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                        <h1><a class="header" href="#notes" id="notes">Notes</a></h1>
<p>A personal collection of notes and cheatsheets.</p>
<p>Source code is located at <a href="https://github.com/johannst/notes">johannst/notes</a>.</p>
<h1><a class="header" href="#tools" id="tools">Tools</a></h1>
<ul>
<li><a href="tools/./zsh.html">zsh</a></li>
<li><a href="tools/./bash.html">bash</a></li>
<li><a href="tools/./fish.html">fish</a></li>
<li><a href="tools/./tmux.html">tmux</a></li>
<li><a href="tools/./git.html">git</a></li>
<li><a href="tools/./awk.html">awk</a></li>
<li><a href="tools/./emacs.html">emacs</a></li>
<li><a href="tools/./gpg.html">gpg</a></li>
<li><a href="tools/./gdb.html">gdb</a></li>
<li><a href="tools/./radare2.html">radare2</a></li>
<li><a href="tools/./qemu.html">qemu</a></li>
</ul>
<h1><a class="header" href="#zsh1" id="zsh1">zsh(1)</a></h1>
<h2><a class="header" href="#keybindings" id="keybindings">Keybindings</a></h2>
<p>Change input mode:</p>
<pre><code class="language-zsh">bindkey -v              change to vi keymap
bindkey -e              change to emacs keymap
</code></pre>
<p>Define key-mappings:</p>
<pre><code class="language-zsh">bindkey                 list mappings in current keymap
bindkey in-str cmd      create mapping for `in-str` to `cmd`
bindkey -r in-str       remove binding for `in-str`

# C-v &lt;key&gt;             dump &lt;key&gt; code, which can be used in `in-str`
# zle -l                list all functions for keybindings
# man zshzle(1)         STANDARD WIDGETS: get description of functions
</code></pre>
<p>Access edit buffer in zle widget:</p>
<pre><code class="language-zsh">$BUFFER       # Entire edit buffer content
$LBUFFER      # Edit buffer content left to cursor
$RBUFFER      # Edit buffer content right to cursor

# create zle widget which adds text right of the cursor
function add-text() {
    RBUFFER=&quot;some text $RBUFFER&quot;
}
zle -N add-text

bindkey &quot;^p&quot; add-text
</code></pre>
<h2><a class="header" href="#parameter" id="parameter">Parameter</a></h2>
<p>Default value:</p>
<pre><code class="language-zsh"># default value
echo ${foo:-defval}   # defval
foo=bar
echo ${foo:-defval}   # bar
</code></pre>
<p>Alternative value:</p>
<pre><code class="language-zsh">echo ${foo:+altval}   # ''
foo=bar
echo ${foo:+altval}   # altval
</code></pre>
<p>Check variable set, error if not set:</p>
<pre><code class="language-zsh">echo ${foo:?msg}      # print `msg` and return errno `1`
foo=bar
echo ${foo:?msg}      # bar
</code></pre>
<p>Sub-string <code>${var:offset:length}</code>:</p>
<pre><code class="language-zsh">foo=abcdef
echo ${foo:1:3}       # bcd
</code></pre>
<p>Trim prefix <code>${var#prefix}</code>:</p>
<pre><code class="language-zsh">foo=bar.baz
echo ${foo#bar}       # .baz
</code></pre>
<p>Trim suffix <code>${var%suffix}</code>:</p>
<pre><code class="language-zsh">foo=bar.baz
echo ${foo%.baz}      # bar
</code></pre>
<p>Substitute pattern <code>${var/pattern/replace}</code>:</p>
<pre><code class="language-zsh">foo=aabbccbbdd
echo ${foo/bb/XX}    # aaXXccbbdd
echo ${foo//bb/XX}   # aaXXccXXdd
# replace prefix
echo ${foo/#bb/XX}   # aabbccbbdd
echo ${foo/#aa/XX}   # XXbbccbbdd
# replace suffix
echo ${foo/%bb/XX}   # aabbccbbdd
echo ${foo/%dd/XX}   # aabbccbbXX
</code></pre>
<blockquote>
<p>Note: <code>prefix</code>/<code>suffix</code>/<code>pattern</code> are expanded as pathnames.</p>
</blockquote>
<h2><a class="header" href="#variables" id="variables">Variables</a></h2>
<pre><code class="language-zsh"># Variable with local scope
local var=val

# Read-only variable
readonly var=bal
</code></pre>
<p>Indexed arrays:</p>
<pre><code class="language-zsh">arr=(aa bb cc dd)
echo $arr[1]           # aa
echo $arr[-1]          # dd

arr+=(ee)
echo $arr[-1]          # ee

echo $arr[1,3]         # aa bb cc
</code></pre>
<p>Associative arrays:</p>
<pre><code class="language-zsh">typeset -A arr
arr[x]='aa'
arr[y]='bb'
echo $arr[x]           # aa
</code></pre>
<p>Tied arrays:</p>
<pre><code class="language-zsh">typeset -T VEC vec=(1 2 3) '|'

echo $vec              # 1 2 3
echo $VEC              # 1|2|3
</code></pre>
<p>Unique arrays (set):</p>
<pre><code>typeset -U vec=(1 2 3)

echo $vec             # 1 2 3
vec+=(1 2 4)
echo $vec             # 1 2 3 4
</code></pre>
<h3><a class="header" href="#expansion-flags" id="expansion-flags">Expansion Flags</a></h3>
<p>Join array to string <code>j:sep:</code>:</p>
<pre><code class="language-zsh">foo=(1 2 3 4)
echo ${(j:-:)foo}     # 1-2-3-4
echo ${(j:\n:)foo}    # join with new lines
</code></pre>
<p>Split string to array <code>s:sep</code>:</p>
<pre><code class="language-zsh">foo='1-2-3-4'
bar=(${(s:-:)foo})    # capture as array
echo $bar             # 1 2 3 4
echo $bar[2]          # 2
</code></pre>
<p>Upper/Lower case string:</p>
<pre><code class="language-zsh">foo=aaBB
echo ${(L)foo}        # aabb
echo ${(U)foo}        # AABB
</code></pre>
<h2><a class="header" href="#argument-parsing-with-zparseopts" id="argument-parsing-with-zparseopts">Argument parsing with <code>zparseopts</code></a></h2>
<pre><code class="language-zsh">zparseopts [-D] [-E] [-A assoc] specs
</code></pre>
<p>Arguments are copied into the associative array <code>assoc</code> according to <code>specs</code>.
Each spec is described by an entry as <code>opt[:][=array]</code>.</p>
<ul>
<li><code>opt</code> is the option without the <code>-</code> char. Passing <code>-f</code> is matched against <code>f</code>
opt, <code>--long</code> is matched against <code>-long</code>.</li>
<li>Using <code>:</code> means the option will take an argument.</li>
<li>The optional <code>=array</code> specifies an alternate storage container where this
option should be stored.</li>
</ul>
<blockquote>
<p>Documentation can be found in <code>man zshmodules</code>.</p>
</blockquote>
<h3><a class="header" href="#example" id="example">Example</a></h3>
<pre><code class="language-zsh">#!/bin/zsh
function test() {
    zparseopts -D -E -A opts f=flag o: -long:
    echo &quot;flag $flag&quot;
    echo &quot;o    $opts[-o]&quot;
    echo &quot;long $opts[--long]&quot;
    echo &quot;pos  $1&quot;
}

test -f -o OPTION --long LONG_OPT POSITIONAL

# Outputs:
#   flag -f
#   o    OPTION
#   long LONG_OPT
#   pos  POSITIONAL
</code></pre>
<h2><a class="header" href="#regular-expressions" id="regular-expressions">Regular Expressions</a></h2>
<p>Zsh supports regular expression matching with the binary operator <code>=~</code>.
The match results can be accessed via the <code>$MATCH</code> variable and
<code>$match</code> indexed array:</p>
<ul>
<li><code>$MATCH</code> contains the full match</li>
<li><code>$match[1]</code> contains match of the first capture group</li>
</ul>
<pre><code class="language-zsh">INPUT='title foo : 1234'
REGEX='^title (.+) : ([0-9]+)$'
if [[ $INPUT =~ $REGEX ]]; then
    echo &quot;$MATCH&quot;       # title foo : 1234
    echo &quot;$match[1]&quot;    # foo
    echo &quot;$match[2]&quot;    # 1234
fi
</code></pre>
<h2><a class="header" href="#completion" id="completion">Completion</a></h2>
<h3><a class="header" href="#installation" id="installation">Installation</a></h3>
<p>Completion functions are provided via files and need to be placed in a location
covered by <code>$fpath</code>. By convention the completion files are names as <code>_&lt;CMD&gt;</code>.</p>
<p>A completion skeleton for the command <code>foo</code>, stored in <code>_foo</code></p>
<pre><code class="language-zsh">#compdef _foo foo

function _foo() {
    ...
}
</code></pre>
<p>Alternatively one can install a completion function explicitly by calling <code>compdef &lt;FUNC&gt; &lt;CMD&gt;</code>.</p>
<h3><a class="header" href="#completion-variables" id="completion-variables">Completion Variables</a></h3>
<p>Following variables are available in Completion functions:</p>
<pre><code class="language-zsh">$words              # array with command line in words
$#words             # number words
$CURRENT            # index into $words for cursor position
$words[CURRENT-1]   # previous word (relative to cursor position)
</code></pre>
<h3><a class="header" href="#completion-functions" id="completion-functions">Completion Functions</a></h3>
<ul>
<li><code>_describe</code>     simple completion, just words + description</li>
<li><code>_arguments</code>    sophisticated completion, allow to specify actions</li>
</ul>
<h4><a class="header" href="#completion-with-a-hrefhttpzshsourceforgenetdocreleasecompletion-systemhtmlcompletion-functions_describea" id="completion-with-a-hrefhttpzshsourceforgenetdocreleasecompletion-systemhtmlcompletion-functions_describea">Completion with <a href="http://zsh.sourceforge.net/Doc/Release/Completion-System.html#Completion-Functions"><code>_describe</code></a></a></h4>
<pre><code class="language-zsh">_describe MSG COMP
</code></pre>
<ul>
<li><code>MSG</code> simple string with header message</li>
<li><code>COMP</code> array of completions where each entry is <code>&quot;opt:description&quot;</code></li>
</ul>
<pre><code class="language-zsh">function _foo() {
    local -a opts
    opts=('bla:desc for bla' 'blu:desc for blu')
    _describe 'foo-msg' opts
}
compdef _foo foo

foo &lt;TAB&gt;&lt;TAB&gt;
 -- foo-msg --
bla  -- desc for bla
blu  -- desc for blu
</code></pre>
<h4><a class="header" href="#completion-with-a-hrefhttpzshsourceforgenetdocreleasecompletion-systemhtmlcompletion-functions_argumentsa" id="completion-with-a-hrefhttpzshsourceforgenetdocreleasecompletion-systemhtmlcompletion-functions_argumentsa">Completion with <a href="http://zsh.sourceforge.net/Doc/Release/Completion-System.html#Completion-Functions"><code>_arguments</code></a></a></h4>
<pre><code class="language-zsh">_arguments SPEC [SPEC...]
</code></pre>
<p>where <code>SPEC</code> can have one of the following forms:</p>
<ul>
<li><code>OPT[DESC]:MSG:ACTION</code></li>
<li><code>N:MSG:ACTION</code></li>
</ul>
<p>Available actions</p>
<pre><code class="language-zsh">(op1 op2)   list possible matches
-&gt;VAL       set $state=VAL and continue, `$state` can be checked later in switch case
FUNC        call func to generate matches
{STR}       evaluate `STR` to generate matches
</code></pre>
<h3><a class="header" href="#example-1" id="example-1">Example</a></h3>
<p>Skeleton to copy/paste for writing simple completions.</p>
<p>Assume a program <code>foo</code> with the following interface:</p>
<pre><code class="language-zsh">foo -c green|red|blue -s low|high -f &lt;file&gt; -d &lt;dir&gt; -h
</code></pre>
<p>The completion handler could be implemented as follows in a file called <code>_foo</code>:</p>
<pre><code class="language-zsh">#compdef _foo foo

function _foo_color() {
    local colors=()
    colors+=('green:green color')
    colors+=('red:red color')
    colors+=('blue:blue color')
    _describe &quot;color&quot; colors
}

function _foo() {
    _arguments                              \
        &quot;-c[define color]:color:-&gt;s_color&quot;  \
        &quot;-s[select sound]:sound:(low high)&quot; \
        &quot;-f[select file]:file:_files&quot;       \
        &quot;-d[select dir]:dir:_files -/&quot;      \
        &quot;-h[help]&quot;

    case $state in
        s_color) _foo_color;;
    esac
}
</code></pre>
<blockquote>
<p><code>_files</code> is a zsh builtin utility function to complete files/dirs see</p>
<ul>
<li><a href="http://zsh.sourceforge.net/Doc/Release/Completion-System.html#Completion-Functions">zsh completion functions</a></li>
<li><a href="https://github.com/zsh-users/zsh-completions/blob/master/zsh-completions-howto.org#utility-functions">zsh completion utility functions</a></li>
</ul>
</blockquote>
<h1><a class="header" href="#bash1" id="bash1">bash(1)</a></h1>
<h2><a class="header" href="#expansion" id="expansion">Expansion</a></h2>
<h3><a class="header" href="#generator" id="generator">Generator</a></h3>
<pre><code class="language-bash"># generate sequence from n to m
{n..m}
# generate sequence from n to m step by s
{n..m..s}

# expand cartesian product
{a,b}{c,d}
</code></pre>
<h3><a class="header" href="#parameter-1" id="parameter-1">Parameter</a></h3>
<pre><code class="language-bash"># default value
bar=${foo:-some_val}  # if $foo set, then bar=$foo else bar=some_val

# alternate value
bar=${foo:+bla $foo}  # if $foo set, then bar=&quot;bla $foo&quot; else bar=&quot;&quot;

# check param set
bar=${foo:?msg}  # if $foo set, then bar=$foo else exit and print msg

# indirect
FOO=foo
BAR=FOO
bar=${!BAR}  # deref value of BAR -&gt; bar=$FOO

# prefix
${foo#prefix}  # remove prefix when expanding $foo
# suffix
${foo%suffix}  # remove suffix when expanding $foo

# substitute
${foo/pattern/string}  # replace pattern with string when expanding foo
# pattern starts with
# '/'   replace all occurences of pattern
# '#'   pattern match at beginning
# '%'   pattern match at end
</code></pre>
<blockquote>
<p>Note: <code>prefix</code>/<code>suffix</code>/<code>pattern</code> are expanded as <a href="tools/bash.html#pathname">pathnames</a>.</p>
</blockquote>
<h3><a class="header" href="#pathname" id="pathname">Pathname</a></h3>
<pre><code class="language-bash">*           match any string
?           match any single char
\\          match backslash
[abc]       match any char of 'a' 'b' 'c'
[a-z]       match any char between 'a' - 'z'
[^ab]       negate, match all not 'a' 'b'
[:class:]   match any char in class, available:
              alnum,alpha,ascii,blank,cntrl,digit,graph,lower,
              print,punct,space,upper,word,xdigit
</code></pre>
<p>Wit <code>extglob</code> shell option enabled it is possible to have more powerful
patterns. In the following <code>pattern-list</code> is one ore more patterns separated
by <code>|</code> char.</p>
<pre><code class="language-bash">?(pattern-list)   matches zero or one occurrence of the given patterns
*(pattern-list)   matches zero or more occurrences of the given patterns
+(pattern-list)   matches one or more occurrences of the given patterns
@(pattern-list)   matches one of the given patterns
!(pattern-list)   matches anything except one of the given patterns
</code></pre>
<blockquote>
<p>Note: <code>shopt -s extglob</code>/<code>shopt -u extglob</code> to enable/disable <code>extglob</code>
option.</p>
</blockquote>
<h2><a class="header" href="#io-redirection" id="io-redirection">I/O redirection</a></h2>
<blockquote>
<p>Note: The trick with bash I/O redirection is to interpret from left-to-right.</p>
</blockquote>
<pre><code class="language-bash"># stdout &amp; stderr to file
command &gt;file 2&gt;&amp;1
# equivalent
command &amp;&gt;file

# stderr to stdout &amp; stdout to file
command 2&gt;&amp;1 &gt;file
</code></pre>
<h3><a class="header" href="#explanation" id="explanation">Explanation</a></h3>
<pre><code class="language-bash">j&gt;&amp;i
</code></pre>
<p>Duplicate <code>fd i</code> to <code>fd j</code>, making <code>j</code> a copy of <code>i</code>. See <a href="http://man7.org/linux/man-pages/man2/dup.2.html">dup2(2)</a>.</p>
<p>Example:</p>
<pre><code class="language-bash">command 2&gt;&amp;1 &gt;file
</code></pre>
<ol>
<li>duplicate <code>fd 1</code> to <code>fd 2</code>, effectively redirecting <code>stderr</code> to <code>stdout</code></li>
<li>redirect <code>stdout</code> to <code>file</code></li>
</ol>
<h2><a class="header" href="#argument-parsing-with-getopts" id="argument-parsing-with-getopts">Argument parsing with <code>getopts</code></a></h2>
<p>The <code>getopts</code> builtin uses following global variables:</p>
<ul>
<li><code>OPTARG</code>, value of last option argument</li>
<li><code>OPTIND</code>, index of the next argument to process (user must reset)</li>
<li><code>OPTERR</code>, display errors if set to <code>1</code></li>
</ul>
<pre><code class="language-bash">getopts &lt;optstring&gt; &lt;param&gt; [&lt;args&gt;]
</code></pre>
<ul>
<li><code>&lt;optstring&gt;</code> specifies the names of supported options, eg <code>f:c</code>
<ul>
<li><code>f:</code> means <code>-f</code> option with an argument</li>
<li><code>c</code> means <code>-c</code> option without an argument</li>
</ul>
</li>
<li><code>&lt;param&gt;</code> specifies a variable name which <code>getopts</code> fills with the last parsed option argument</li>
<li><code>&lt;args&gt;</code> optionally specify argument string to parse, by default <code>getopts</code> parses <code>$@</code></li>
</ul>
<h3><a class="header" href="#example-2" id="example-2">Example</a></h3>
<pre><code class="language-bash">#!/bin/bash
function parse_args() {
    while getopts &quot;f:c&quot; PARAM; do
        case $PARAM in
            f) echo &quot;GOT -f $OPTARG&quot;;;
            c) echo &quot;GOT -c&quot;;;
            *) echo &quot;ERR: print usage&quot;; exit 1;;
        esac
    done
    # users responsibility to reset OPTIND
    OPTIND=1
}

parse_args -f xxx -c
parse_args -f yyy
</code></pre>
<h2><a class="header" href="#regular-expressions-1" id="regular-expressions-1">Regular Expressions</a></h2>
<p>Bash supports regular expression matching with the binary operator <code>=~</code>.
The match results can be accessed via the <code>$BASH_REMATCH</code> variable:</p>
<ul>
<li><code>${BASH_REMATCH[0]}</code> contains the full match</li>
<li><code>${BASH_REMATCH[1]}</code> contains match of the first capture group</li>
</ul>
<pre><code class="language-bash">INPUT='title foo : 1234'
REGEX='^title (.+) : ([0-9]+)$'
if [[ $INPUT =~ $REGEX ]]; then
    echo &quot;${BASH_REMATCH[0]}&quot;    # title foo : 1234
    echo &quot;${BASH_REMATCH[1]}&quot;    # foo
    echo &quot;${BASH_REMATCH[2]}&quot;    # 1234
fi
</code></pre>
<blockquote>
<p><strong>Caution</strong>: When specifying a <code>regex</code> in the <code>[[ ]]</code> block directly, quotes will be treated as part of the pattern.
<code>[[ $INPUT =~ &quot;foo&quot; ]]</code> will match against <code>&quot;foo&quot;</code> not <code>foo</code>!</p>
</blockquote>
<h2><a class="header" href="#completion-1" id="completion-1">Completion</a></h2>
<p>The <code>complete</code> builtin is used to interact with the completion system.</p>
<pre><code class="language-bash">complete                    # print currently installed completion handler
complete -F &lt;func&gt; &lt;cmd&gt;    # install &lt;func&gt; as completion handler for &lt;cmd&gt;
complete -r &lt;cmd&gt;           # uninstall completion handler for &lt;cmd&gt;
</code></pre>
<p>Variables available in completion functions:</p>
<pre><code class="language-bash"># in
$1              # &lt;cmd&gt;
$2              # current word
$3              # privous word

COMP_WORDS      # array with current command line words
COMP_CWORD      # index into COMP_WORDS with current cursor position

# out
COMPREPLY       # array with possible completions
</code></pre>
<p>The <code>compgen</code> builtin is used to generate possible matches by comparing <code>word</code>
against words generated by <code>option</code>.</p>
<pre><code class="language-bash">compgen &lt;option&gt; &lt;word&gt;

# usefule options:
# -W &lt;list&gt;    specify list of possible completions
# -d           generate list with dirs
# -f           generate list with files
# -u           generate list with users
# -e           generate list with exported variables

# compare &quot;f&quot; against words &quot;foo&quot; &quot;foobar&quot; &quot;bar&quot; and generate matches
compgen -W &quot;foo foobar bar&quot; &quot;f&quot;

# compare &quot;hom&quot; against file/dir names and generate matches
compgen -d -f &quot;hom&quot;
</code></pre>
<h3><a class="header" href="#example-3" id="example-3">Example</a></h3>
<p>Skeleton to copy/paste for writing simple completions.</p>
<p>Assume a program <code>foo</code> with the following interface:</p>
<pre><code class="language-bash">foo -c green|red|blue -s low|high -f &lt;file&gt; -h
</code></pre>
<p>The completion handler could be implemented as follows:</p>
<pre><code class="language-bash">function _foo() {
    local curr=$2
    local prev=$3

    local opts=&quot;-c -s -f -h&quot;
    case $prev in
        -c) COMPREPLY=( $(compgen -W &quot;green red blue&quot; -- $curr) );;
        -s) COMPREPLY=( $(compgen -W &quot;low high&quot; -- $curr) );;
        -f) COMPREPLY=( $(compgen -f -- $curr) );;
        *)  COMPREPLY=( $(compgen -W &quot;$opts&quot; -- $curr) );;
    esac
}

complete -F _foo foo
</code></pre>
<h1><a class="header" href="#fish1" id="fish1">fish(1)</a></h1>
<h2><a class="header" href="#quick-info" id="quick-info">Quick Info</a></h2>
<p>Fish initialization file <code>~/.config/fish/config.fish</code></p>
<p>Switch between different key bindings:</p>
<ul>
<li><code>fish_default_key_bindings</code> to use default key bindings</li>
<li><code>fish_vi_key_bindings</code> to use vi key bindings</li>
</ul>
<h2><a class="header" href="#variables-1" id="variables-1">Variables</a></h2>
<p>Available scopes</p>
<ul>
<li><code>local</code> variable local to a block</li>
<li><code>global</code> variable global to shell instance</li>
<li><code>universal</code> variable universal to all shell instances + preserved across
shell restart</li>
</ul>
<h3><a class="header" href="#setunset-variables" id="setunset-variables">Set/Unset Variables</a></h3>
<pre><code class="language-text">set &lt;name&gt; [&lt;values&gt;]
    -l  local scope
    -g  global scope
    -U  universal scope
    -e  erase variable
    -S  show verbose info
    -x  export to ENV
    -u  unexport from ENV
</code></pre>
<h3><a class="header" href="#lists" id="lists">Lists</a></h3>
<p>In <code>fish</code> all variables are lists (start with index <code>1</code>, but lists can't
contain lists.</p>
<pre><code class="language-text">set foo a b c d

echo $foo[1]      # a
echo $foo[-1]     # d
echo $foo[2..3]   # b c
echo $foo[1 3]    # a c
</code></pre>
<p><code>$</code> can be seen as dereference operator.</p>
<pre><code class="language-text">set foo a; set a 1337
echo $$foo  # outputs 1337
</code></pre>
<p>Cartesian product.</p>
<pre><code class="language-text">echo file.{h,cc}
# file.h file.cc

echo {a,b}{1,2}
# a1 b1 b2
</code></pre>
<h3><a class="header" href="#special-variables-lists" id="special-variables-lists">Special Variables (Lists)</a></h3>
<pre><code class="language-text">$status      # exit code of last command
$pipestatus  # list of exit codes of pipe chain

$CMD_DURATION   # runtime of last command in ms
</code></pre>
<h4><a class="header" href="#path" id="path"><code>*PATH</code></a></h4>
<p>Lists ending with <code>PATH</code> are automatically split at <code>:</code> when used and joined
with <code>:</code> when exported to the environment.</p>
<pre><code class="language-text">set -x BLA_PATH a:b:c:d
echo $BLA_PATH              # a b c d
env | grep BLA_PATH         # BLA_PATH=a:b:c:d
</code></pre>
<h2><a class="header" href="#command-handling" id="command-handling">Command Handling</a></h2>
<pre><code class="language-text"># sub-commands are not run in quotes
echo &quot;ls output: &quot;(ls)
</code></pre>
<h3><a class="header" href="#io-redirection-1" id="io-redirection-1">I/O redirection</a></h3>
<pre><code class="language-text"># 'noclobber', fail if 'log' already exists
echo foo &gt;? log
</code></pre>
<h2><a class="header" href="#control-flow" id="control-flow">Control Flow</a></h2>
<h3><a class="header" href="#if--else" id="if--else"><code>if</code> / <code>else</code></a></h3>
<pre><code class="language-text">if grep foo bar
    # do sth
else if grep foobar bar
    # do sth else
else
    # do sth else
end
</code></pre>
<h3><a class="header" href="#switch" id="switch"><code>switch</code></a></h3>
<pre><code class="language-text">switch (echo foo)
case 'foo*'
    # do start with foo
case bar dudel
    # do bar and dudel
case '*'
    # do else
end
</code></pre>
<h3><a class="header" href="#while-loop" id="while-loop"><code>while</code> Loop</a></h3>
<pre><code class="language-text">while true
    echo foo
end
</code></pre>
<h3><a class="header" href="#for-loop" id="for-loop"><code>for</code> Loop</a></h3>
<pre><code class="language-text">for f in (ls)
    echo $f
end
</code></pre>
<h2><a class="header" href="#functions" id="functions">Functions</a></h2>
<p>Function arguments are passed via <code>$argv</code> list.</p>
<pre><code class="language-text">function fn_foo
    echo $argv
end
</code></pre>
<h3><a class="header" href="#autoloading" id="autoloading">Autoloading</a></h3>
<p>When running a command fish attempts to autoload a function. The shell looks
for <code>&lt;cmd&gt;.fish</code> in the locations defined by <code>$fish_function_path</code> and loads
the function lazily if found.</p>
<p>This is the preferred way over monolithically defining all functions in a
startup script.</p>
<h3><a class="header" href="#helper" id="helper">Helper</a></h3>
<pre><code class="language-text">functions         # list al functions
functions foo     # describe function 'foo'
functions -e foo  # erase function 'foo'

funced foo        # edit function 'foo'
                  # '-e vim' to edit in vim
</code></pre>
<h2><a class="header" href="#prompt" id="prompt">Prompt</a></h2>
<p>The prompt is defined by the output of the <code>fish_prompt</code> function.</p>
<pre><code class="language-text">function fish_prompt
    set -l cmd_ret
    echo &quot;&gt; &quot;(pwd) $cmd_ret&quot; &quot;
end
</code></pre>
<blockquote>
<p>Use <code>set_color</code> to manipulate terminal colors.</p>
</blockquote>
<h2><a class="header" href="#useful-builtins" id="useful-builtins">Useful Builtins</a></h2>
<pre><code class="language-text"># history
history search &lt;str&gt;   # search history for &lt;str&gt;
history merge          # merge histories from fish sessions

# list
count $var            # count elements in list

# string
string split SEP STRING
</code></pre>
<h2><a class="header" href="#keymaps" id="keymaps">Keymaps</a></h2>
<pre><code class="language-text">  Shift-Tab ........... tab-completion with search
  Alt-Up / Alt-Down ... search history with token under the cursor
  Alt-l ............... list content of dir under cursor
  Alt-p ............... append '2&gt;&amp;1 | less;' to current cmdline
</code></pre>
<h2><a class="header" href="#debug" id="debug">Debug</a></h2>
<pre><code class="language-text">  status print-stack-trace .. prints function stacktrace (can be used in scripts)
  breakpoint ................ halt script execution and gives shell (C-d | exit
                              to continue)
</code></pre>
<h1><a class="header" href="#tmux1" id="tmux1">tmux(1)</a></h1>
<p>Terminology:</p>
<ul>
<li><code>session</code> is a collection of pseudo terminals which can have multiple
<code>windows</code></li>
<li><code>window</code> uses the entire screen and can be split into rectangular <code>panes</code></li>
<li><code>pane</code> is a single pseudo terminal instance</li>
</ul>
<h1><a class="header" href="#tmux-cli" id="tmux-cli">Tmux cli</a></h1>
<pre><code class="language-markdown"># Session
tmux                        creates new session
tmux ls                     list running sessions
tmux kill-session -t &lt;s&gt;    kill running session &lt;s&gt;
tmux attach -t &lt;s&gt; [-d]     attach to session &lt;s&gt;, detach other clients [-d]
tmux detach -s &lt;s&gt;          detach all clients from session &lt;s&gt;

# Environment
tmux showenv -g             show global tmux environment variables
tmux setenv -g &lt;var&gt; &lt;val&gt;  set variable in global tmux env

# Misc
tmux source-file &lt;file&gt;     source config &lt;file&gt;
tmux lscm                   list available tmux commnds
tmux show -g                show global tmux options
tmux display &lt;msg&gt;          display message in tmux status line
</code></pre>
<h2><a class="header" href="#scripting" id="scripting">Scripting</a></h2>
<pre><code class="language-markdown"># Session
tmux list-sessions -F '#S'           list running sessions, only IDs

# Window
tmux list-windows -F '#I' -t &lt;s&gt;     list window IDs for session &lt;s&gt;
tmux selectw -t &lt;s&gt;:&lt;w&gt;              select window &lt;w&gt; in session &lt;s&gt;

# Pane
tmux list-panes -F '#P' -t &lt;s&gt;:&lt;w&gt;   list pane IDs for window &lt;w&gt; in session &lt;s&gt;
tmux selectp -t &lt;s&gt;:&lt;w&gt;.&lt;p&gt;          select pane &lt;p&gt; in window &lt;w&gt; in session &lt;s&gt;

# Run commands
tmux send -t &lt;s&gt;:&lt;w&gt;.&lt;p&gt; &quot;ls&quot; C-m    send cmds/keys to pane
tmux run -t &lt;p&gt; &lt;sh-cmd&gt;             run shell command &lt;sh-cmd&gt; in background and report output on pane -t &lt;p&gt;
</code></pre>
<p>For example cycle through all panes in all windows in all sessions:</p>
<pre><code class="language-bash"># bash
for s in $(tmux list-sessions -F '#S'); do
    for w in $(tmux list-windows -F '#I' -t $s); do
        for p in $(tmux list-panes -F '#P' -t $s:$w); do
            echo $s:$w.$p
        done
    done
done
</code></pre>
<h1><a class="header" href="#bindings" id="bindings">Bindings</a></h1>
<pre><code class="language-markdown">prefix d    detach from current session
prefix c    create new window
prefix w    open window list
prefix $    rename session
prefix ,    rename window
prefix .    move current window
</code></pre>
<p>Following bindings are specific to my <a href="https://github.com/johannst/dotfiles/blob/master/tmux.conf"><code>tmux.conf</code></a>:</p>
<pre><code class="language-markdown">C-s         prefix

# Panes
prefix s    horizontal split
prefix v    vertical split
prefix f    toggle maximize/minimize current pane

# Movement
prefix Tab  toggle between window

prefix h    move to pane left
prefix j    move to pane down
prefix k    move to pane up
prefix l    move to pane right

# Resize
prefix C-h  resize pane left
prefix C-j  resize pane down
prefix C-k  resize pane up
prefix C-l  resize pane right

# Copy/Paste
prefix C-v    enter copy mode
prefix C-p    paste yanked text
prefix C-b    open copy-buffer list

# In Copy Mode
v     enable visual mode
y     yank selected text
</code></pre>
<h1><a class="header" href="#command-mode" id="command-mode">Command mode</a></h1>
<p>To enter command mode <code>prefix :</code>.</p>
<p>Some useful commands are:</p>
<pre><code class="language-markdown">setw synchronize-panes on/off       enables/disables synchronized input to all panes
list-keys -t vi-copy                list keymaps for vi-copy mode
</code></pre>
<h1><a class="header" href="#git1" id="git1">git(1)</a></h1>
<h2><a class="header" href="#staging" id="staging">staging</a></h2>
<pre><code class="language-markdown">  git add -p [&lt;file&gt;] ............ partial staging (interactive)
</code></pre>
<h2><a class="header" href="#remote" id="remote">Remote</a></h2>
<pre><code class="language-markdown">  git remote -v .................. list remotes verbose (with URLs)
  git remote show [-n] &lt;remote&gt; .. list info for &lt;remote&gt; (like remote HEAD,
                                   remote branches, tracking mapping)
</code></pre>
<h2><a class="header" href="#branching" id="branching">Branching</a></h2>
<pre><code class="language-markdown">  git branch [-a] ................ list available branches; -a to include
                                   remote branches
  git branch -vv ................. list branch &amp; annotate with head sha1 &amp;
                                   remote tracking branch
  git branch &lt;bname&gt; ............. create branch with name &lt;bname&gt;
  git checkout &lt;bname&gt; ........... switch to branch with name &lt;bname&gt;
  git checkout --track &lt;branch&gt; .. start to locally track a remote branch
  git push -u origin &lt;rbname&gt; .... push branch to origin (or other remote), and
                                   setup &lt;rbname&gt; as tracking branch
</code></pre>
<h2><a class="header" href="#resetting" id="resetting">Resetting</a></h2>
<pre><code class="language-markdown">  git reset [opt] &lt;ref|commit&gt;
    opt:
      --mixed .................... resets index, but not working tree
      --hard ..................... matches the working tree and index to that
                                   of the tree being switched to any changes to
                                   tracked files in the working tree since
                                   &lt;commit&gt; are lost
  git reset HEAD &lt;file&gt; .......... remove file from staging
  git reset --soft HEAD~1 ........ delete most recent commit but keep work
  git reset --hard HEAD~1 ........ delete most recent commit and delete work
</code></pre>
<h2><a class="header" href="#tags" id="tags">Tags</a></h2>
<pre><code class="language-markdown">  git tag -a &lt;tname&gt; -m &quot;descr&quot; ........ creates an annotated tag (full object
                                         containing tagger, date, ...)
  git tag -l ........................... list available tags
  git checkout tag/&lt;tname&gt; ............. checkout specific tag
  git checkout tag/&lt;tname&gt; -b &lt;bname&gt; .. checkout specific tag in a new branch
</code></pre>
<h2><a class="header" href="#diff" id="diff">Diff</a></h2>
<pre><code class="language-markdown">  git diff HEAD:&lt;fname&gt; origin/HEAD:&lt;fname&gt; ... diff files for different refs
  git diff -U$(wc -l &lt;fname&gt;) &lt;fname&gt; ......... shows complete file with diffs
                                                instead of usual diff snippets
</code></pre>
<h2><a class="header" href="#log" id="log">Log</a></h2>
<pre><code class="language-markdown">  git log --oneline .... shows log in single line per commit -&gt; alias for
                         '--pretty=oneline --abbrev-commit'
  git log --graph ...... text based graph of commit history
  git log --decorate ... decorate log with REFs
</code></pre>
<h2><a class="header" href="#file-history" id="file-history">File history</a></h2>
<pre><code class="language-markdown">  git log -p &lt;file&gt; ......... show commit history + diffs for &lt;file&gt;
  git log --oneline &lt;file&gt; .. show commit history for &lt;file&gt; in compact format
</code></pre>
<h2><a class="header" href="#patching" id="patching">Patching</a></h2>
<pre><code class="language-markdown">  git format-patch &lt;opt&gt; &lt;since&gt;/&lt;revision range&gt;
    opt:
      -N ................... use [PATCH] instead [PATCH n/m] in subject when
                             generating patch description (for patches spanning
                             multiple commits)
      --start-number &lt;n&gt; ... start output file generation with &lt;n&gt; as start
                             number instead '1'
    since spcifier:
      -3 .................. e.g: create a patch from last three commits
      &lt;commit hash&gt; ....... create patch with commits starting after &lt;commit hash&gt;

  git am &lt;patch&gt; ......... apply patch and create a commit for it

  git apply --stat &lt;PATCH&gt; ... see which files the patch would change
  git apply --check &lt;PATCH&gt; .. see if the patch can be applied cleanly
  git apply &lt;PATCH&gt; .......... apply the patch locally without creating a commit

  # eg: generate patches for each commit from initial commit on
  git format-patch -N $(git rev-list --max-parents=0 HEAD)

  # generate single patch file from a certain commit/ref
  git format-patch &lt;COMMIT/REF&gt; --stdout &gt; my-patch.patch
</code></pre>
<h2><a class="header" href="#submodules" id="submodules">Submodules</a></h2>
<pre><code class="language-markdown">  git submodule add &lt;url&gt; [&lt;path&gt;] .......... add new submodule to current project
  git clone --recursive &lt;url&gt; ............... clone project and recursively all
                                              submodules (same as using
                                              'git submodule update --init
                                              --recursive' after clone)
  git submodule update --init --recursive ... checkout submodules recursively
                                              using the commit listed in the
                                              super-project (in detached HEAD)
  git submodule update --remote &lt;submod&gt; .... fetch &amp; merge remote changes for
                                              &lt;submod&gt;, this will pull
                                              origin/HEAD or a branch specified
                                              for the submodule
  git diff --submodule ...................... show commits that are part of the
                                              submodule diff
</code></pre>
<h2><a class="header" href="#inspection" id="inspection">Inspection</a></h2>
<pre><code class="language-markdown">  git ls-tree [-r] &lt;ref&gt; .... show git tree for &lt;ref&gt;, -r to recursively ls sub-trees
  git show &lt;obj&gt; ............ show &lt;obj&gt;
  git cat-file -p &lt;obj&gt; ..... print content of &lt;obj&gt;
</code></pre>
<h2><a class="header" href="#revision-specifier" id="revision-specifier">Revision Specifier</a></h2>
<pre><code class="language-markdown">  HEAD ........ last commit
  HEAD~1 ...... last commit-1
  HEAD~N ...... last commit-N (linear backwards when in tree structure, check
                difference between HEAD^ and HEAD~)
  git rev-list --max-parents=0 HEAD ........... first commit
</code></pre>
<h1><a class="header" href="#awk1" id="awk1">awk(1)</a></h1>
<pre><code class="language-markdown">awk [opt] program [input]
    -F &lt;sepstr&gt;        field separator string (can be regex)
    program            awk program
    input              file or stdin if not file given
</code></pre>
<h2><a class="header" href="#input-processing" id="input-processing">Input processing</a></h2>
<p>Input is processed in two stages:</p>
<ol>
<li>Splitting input into a sequence of <code>records</code>.
By default split at <code>newline</code> character, but can be changed via the
builtin <code>RS</code> variable.</li>
<li>Splitting a <code>record</code> into <code>fields</code>. By default strings without <code>whitespace</code>,
but can be changed via the builtin variable <code>FS</code> or command line option
<code>-F</code>.</li>
</ol>
<p>Fields are accessed as follows:</p>
<ul>
<li><code>$0</code> whole <code>record</code></li>
<li><code>$1</code> field one</li>
<li><code>$2</code> field two</li>
<li>...</li>
</ul>
<h2><a class="header" href="#program" id="program">Program</a></h2>
<p>An <code>awk</code> program is composed of pairs of the form:</p>
<pre><code class="language-markdown">pattern { action }
</code></pre>
<p>The program is run against each <code>record</code> in the input stream. If a <code>pattern</code>
matches a <code>record</code> the corresponding <code>action</code> is executed and can access the
<code>fields</code>.</p>
<pre><code class="language-markdown">INPUT
  |
  v
record ----&gt; ∀ pattern matched
  |                   |
  v                   v
fields ----&gt; run associated action
</code></pre>
<p>Any valid awk <code>expr</code> can be a <code>pattern</code>.</p>
<h3><a class="header" href="#special-pattern" id="special-pattern">Special pattern</a></h3>
<p>awk provides two special patterns, <code>BEGIN</code> and <code>END</code>, which can be used
multiple times. Actions with those patterns are <strong>executed exactly once</strong>.</p>
<ul>
<li><code>BEGIN</code> actions are run before processing the first record</li>
<li><code>END</code> actions are run after processing the last record</li>
</ul>
<h3><a class="header" href="#special-variables" id="special-variables">Special variables</a></h3>
<ul>
<li><code>RS</code> <em>record separator</em>: first char is the record separator, by default
<newline></li>
<li><code>FS</code> <em>field separator</em>: regex to split records into fields, by default
<space></li>
<li><code>NR</code> <em>number record</em>: number of current record</li>
<li><code>NF</code> <em>number fields</em>: number of fields in the current record</li>
</ul>
<h3><a class="header" href="#special-statements--functions" id="special-statements--functions">Special statements &amp; functions</a></h3>
<ul>
<li>
<p><code>printf &quot;fmt&quot;, args...</code></p>
<p>Print format string, args are comma separated.</p>
<ul>
<li><code>%s</code> string</li>
<li><code>%d</code> decimal</li>
<li><code>%x</code> hex</li>
<li><code>%f</code> float</li>
</ul>
<p>Width can be specified as <code>%Ns</code>, this reserves <code>N</code> chars for a string.
For floats one can use <code>%N.Mf</code>, <code>N</code> is the total number including <code>.</code> and
<code>M</code>.</p>
</li>
<li>
<p><code>strftime(&quot;fmt&quot;)</code></p>
<p>Print time stamp formatted by <code>fmt</code>.</p>
<ul>
<li><code>%Y</code> full year (eg 2020)</li>
<li><code>%m</code> month (01-12)</li>
<li><code>%d</code> day (01-31)</li>
<li><code>%F</code> alias for <code>%Y-%m-%d</code></li>
<li><code>%H</code> hour (00-23)</li>
<li><code>%M</code> minute (00-59)</li>
<li><code>%S</code> second (00-59)</li>
<li><code>%T</code> alias for <code>%H:%M:%S</code></li>
</ul>
</li>
</ul>
<h2><a class="header" href="#examples" id="examples">Examples</a></h2>
<h3><a class="header" href="#filter-records" id="filter-records">Filter records</a></h3>
<pre><code class="language-bash">awk 'NR%2 == 0 { print $0 }' &lt;file&gt;
</code></pre>
<p>The pattern <code>NR%2 == 0</code> matches every second record and the action <code>{ print $0 }</code>
prints the whole record.</p>
<h3><a class="header" href="#access-last-fields-in-records" id="access-last-fields-in-records">Access last fields in records</a></h3>
<pre><code class="language-bash">echo 'a b c d e f' | awk '{ print $NF $(NF-1) }'
</code></pre>
<p>Access last fields with arithmetic on the <code>NR</code> number of fields variable.</p>
<h3><a class="header" href="#capture-in-variables" id="capture-in-variables">Capture in variables</a></h3>
<pre><code class="language-bash"># /proc/&lt;pid&gt;/status
#   Name:    cat
#   ...
#   VmRSS:   516 kB
#   ...

for f in /proc/*/status; do
    cat $f | awk '
             /^VmRSS/ { rss = $2/1024 }
             /^Name/ { name = $2 }
             END { printf &quot;%16s %6d MB\n&quot;, name, rss }';
done | sort -k2 -n
</code></pre>
<p>We capture values from <code>VmRSS</code> and <code>Name</code> into variables and print them at the
<code>END</code> once processing all records is done.</p>
<h3><a class="header" href="#run-shell-command-and-capture-output" id="run-shell-command-and-capture-output">Run shell command and capture output</a></h3>
<pre><code class="language-bash">cat /proc/1/status | awk '
                     /^Pid/ {
                        &quot;ps --no-header -o user &quot; $2 | getline user;
                         print user
                     }'
</code></pre>
<p>We build a <code>ps</code> command line and capture the first line of the processes output
in the <code>user</code> variable and then print it.</p>
<h1><a class="header" href="#emacs1" id="emacs1">emacs(1)</a></h1>
<h2><a class="header" href="#help" id="help">help</a></h2>
<pre><code class="language-markdown">  C-h ?         list available help modes
  C-h e         show message output (`*Messages*` buffer)
  C-h f         describe function
  C-h v         describe variable
  C-h w         describe which key invoke function (where-is)
  C-h c &lt;KEY&gt;   print command bound to &lt;KEY&gt;
  C-h k &lt;KEY&gt;   describe command bound to &lt;KEY&gt;
  C-h b         list buffer local key-bindings
  &lt;kseq&gt; C-h    list possible key-bindings with &lt;kseq&gt;
                eg C-x C-h -&gt; list key-bindings beginning with C-x
</code></pre>
<h2><a class="header" href="#package-manager" id="package-manager">package manager</a></h2>
<pre><code class="language-markdown">  key    fn                          description
------------------------------------------------
         package-refresh-contents    refresh package list
         package-list-packages       list available/installed packages
                                     `U x` to mark packages for Upgrade &amp; eXecute
</code></pre>
<h2><a class="header" href="#window" id="window">window</a></h2>
<pre><code class="language-markdown">  key      fn                      description
----------------------------------------------
  C-x 0    delete-window           kill focused window
  C-x 1    delete-other-windows    kill all other windows
  C-x 2    split-window-below      split horizontal
  C-x 3    split-window-right      split vertical
  C-x o    other-window            other window (cycle)
</code></pre>
<h2><a class="header" href="#buffer" id="buffer">buffer</a></h2>
<pre><code class="language-markdown">  key        fn                   description
---------------------------------------------
  C-x C-q    read-only-mode       toggle read-only mode for buffer
  C-x k      kill-buffer          kill buffer
  C-x s      save-some-buffers    save buffer
  C-x w      write-file           write buffer (save as)
  C-x b      switch-to-buffer     switch buffer
  C-x C-b    list-buffers         buffer list
</code></pre>
<h2><a class="header" href="#ibuffer" id="ibuffer">ibuffer</a></h2>
<p>Builtin advanced buffer selection mode</p>
<pre><code class="language-markdown">  key        fn            description
--------------------------------------
             ibuffer       enter buffer selection

  h                        ibuffer help

  o                        open buffer in other window
  C-o                      open buffer in other window keep focus in ibuffer

  s a                      sort by buffer name
  s f                      sort by file name
  s v                      sort by last viewed
  s v                      sort by major mode
  ,                        cycle sorting mode

  =                        compare buffer against file on disk (if file is dirty `*`)

  /m                       filter by major mode
  /n                       filter by buffer name
  /f                       filter by file name
  //                       remove all filter

  /g                       create filter group
  /\                       remove all filter groups
</code></pre>
<h2><a class="header" href="#isearch" id="isearch">isearch</a></h2>
<pre><code class="language-markdown">  key    fn                           description
-------------------------------------------------
  C-s    isearch-forward              search forward from current position (C-s to go to next match)
  C-r    isearch-backward             search backwards from current position (C-r to go to next match)
  C-w    isearch-yank-word-or-char    feed next word to current search (extend)
  M-p    isearch-ring-advance         previous search input
  M-n    isearch-ring-retreat         next search input
</code></pre>
<h2><a class="header" href="#occur" id="occur">occur</a></h2>
<pre><code class="language-markdown">  key      fn           description
-----------------------------------
  M-s o    occur        get matches for regexp in buffer
                        use during `isearch` to use current search term

  C-n                   goto next line
  C-p                   goto previous line
  o                     open match in other window
  C-o                   open match in other window keep focus in ibuffer
</code></pre>
<pre><code class="language-markdown">  key      fn                                 description
---------------------------------------------------------
           multi-occur-in-matching-buffers    run occur in buffers matching regexp
</code></pre>
<h2><a class="header" href="#grep" id="grep">grep</a></h2>
<pre><code class="language-markdown">  key    fn           description
-----------------------------------
         rgrep        recursive grep
         find-grep    run find-grep result in *grep* buffer

  n/p                 navigate next/previous match in *grep* buffer
  q                   quit *grep* buffer
</code></pre>
<h2><a class="header" href="#yankpaste" id="yankpaste">yank/paste</a></h2>
<pre><code class="language-markdown">  key         fn                  description
---------------------------------------------
  C-&lt;SPACE&gt;   set-mark-command    set start mark to select text
  M-w         kill-ring-save      copy selected text
  C-w         kill-region         kill selected text
  C-y         yank                paste selected text
  M-y         yank-pop            cycle through kill-ring (only after paste)
</code></pre>
<h2><a class="header" href="#register" id="register">register</a></h2>
<pre><code class="language-markdown">  key             fn                 description
------------------------------------------------
  C-x r s &lt;reg&gt;   copy-to-register   save region in register &lt;reg&gt;
  C-x r i &lt;reg&gt;   insert-register    insert content of register &lt;reg&gt;
</code></pre>
<h2><a class="header" href="#blockrect" id="blockrect">block/rect</a></h2>
<pre><code class="language-markdown">  key          fn                    description
------------------------------------------------
  C-x &lt;SPC&gt;    rectangle-mark-mode   activate rectangle-mark-mode
               string-rectangle      insert text in marked rect
</code></pre>
<h2><a class="header" href="#mass-edit" id="mass-edit">mass edit</a></h2>
<pre><code class="language-markdown">  key       fn                       description
------------------------------------------------
  C-x h     mark-whole-buffer        mark whole buffer
            delete-matching-line     delete lines matching regex
  M-%       query-replace            search &amp; replace
  C-M-%     query-replace-regexp     search &amp; replace regex
</code></pre>
<h2><a class="header" href="#narrow" id="narrow">narrow</a></h2>
<pre><code class="language-markdown">  key       fn                    description
---------------------------------------------
  C-x n n   narrow-to-region      show only focused region (narrow)
  C-x n w   widen                 show whole buffer (wide)
</code></pre>
<h2><a class="header" href="#org" id="org">org</a></h2>
<pre><code class="language-markdown">  key              fn   description
------------------------------------
  M-up/M-down           re-arrange items in same hierarchy
  M-left/M-right        change item hierarchy
  C-RET                 create new item below current
  C-S-RET               create new TODO item below current
  S-left/S-right        cycle TODO states
</code></pre>
<h3><a class="header" href="#org-source" id="org-source">org source</a></h3>
<pre><code class="language-markdown">  key       fn     description
------------------------------
  &lt;s TAB           generate a source block
  C-c '            edit source block (in lang specific buffer)
  C-c C-c          eval source block
</code></pre>
<h2><a class="header" href="#comapny" id="comapny">comapny</a></h2>
<pre><code class="language-markdown">  key         fn   description
-------------------------------
  C-s              search through completion candidates
  C-o              filter completion candidates based on search term
  &lt;f1&gt;             get doc for completion condidate
  M-&lt;digit&gt;        select completion candidate
</code></pre>
<h2><a class="header" href="#tags-1" id="tags-1">tags</a></h2>
<p>To generate <code>etags</code> using <code>ctags</code></p>
<pre><code class="language-markdown">  ctags -R -e .         generate emacs tag file (important `-e`)
</code></pre>
<p>Navigate using tags</p>
<pre><code class="language-markdown">  key      fn                       description
-----------------------------------------------
           xref-find-definitions    find definition of tag
           xref-find-apropos        find symbols matching regexp
           xref-find-references     find references of tag
</code></pre>
<h2><a class="header" href="#lisp" id="lisp">lisp</a></h2>
<pre><code class="language-markdown">  key   fn        description
------------------------------
        ielm      open interactive elips shell
</code></pre>
<p>In <code>lisp-interaction-mode</code> (<code>*scratch*</code> buffer by defult)</p>
<pre><code class="language-markdown">  key              fn                        description
--------------------------------------------------------
  C-j              eval-print-last-sexp      evaluate &amp; print preceeding lisp expr

  C-x C-e          eval-last-sexp            evaluate lisp expr
  C-u C-x C-e      eval-last-sexp            evaluate &amp; print
</code></pre>
<h2><a class="header" href="#ido" id="ido">ido</a></h2>
<p>Builtin fuzzy completion mode (eg buffer select, dired, ...).</p>
<pre><code class="language-markdown">  key              fn          description
------------------------------------------
                  ido-mode     toggle ido mode
  &lt;Left&gt;/&lt;Right&gt;               cycle through available competions
  &lt;RET&gt;                        select completion
</code></pre>
<h2><a class="header" href="#evil" id="evil">evil</a></h2>
<pre><code class="language-markdown">  key    fn    description
--------------------------
  C-z          toggle emacs/evil mode
  C-^          toggle between previous and current buffer
  C-p          after paste cycle kill-ring back
  C-n          after paste cycle kill-ring forward
</code></pre>
<h2><a class="header" href="#dired" id="dired">dired</a></h2>
<pre><code class="language-markdown">  key    fn    description
--------------------------
  i            open sub-dir in same buffer
  +            create new directory
  C            copy file/dir

  q            quit
</code></pre>
<h1><a class="header" href="#gpg1" id="gpg1">gpg(1)</a></h1>
<pre><code>gpg
  -o|--output                 Specify output file
  -a|--armor                  Create ascii output
  -u|--local-user &lt;name&gt;      Specify key for signing
  -r|--recipient              Encrypt for user
</code></pre>
<h2><a class="header" href="#generate-new-keypair" id="generate-new-keypair">Generate new keypair</a></h2>
<pre><code class="language-bash">gpg --full-generate-key
</code></pre>
<h2><a class="header" href="#list-keys" id="list-keys">List keys</a></h2>
<pre><code>gpg -k / --list-key               # public keys
gpg -K / --list-secret-keys       # secret keys
</code></pre>
<h2><a class="header" href="#edit-keys" id="edit-keys">Edit keys</a></h2>
<pre><code class="language-bash">gpg --edit-key &lt;KEY ID&gt;
</code></pre>
<p>Gives prompt to modify <code>KEY ID</code>, common commands:</p>
<pre><code class="language-bash">help         show help
save         save &amp; quit

list         list keys and user IDs
key &lt;N&gt;      select subkey &lt;N&gt;
uid &lt;N&gt;      select user ID &lt;N&gt;

expire       change expiration of selected key

adduid       add user ID
deluid       delete selected user ID

addkey       add subkey
delkey       delete selected subkey
</code></pre>
<h2><a class="header" href="#export--import-keys" id="export--import-keys">Export &amp; Import Keys</a></h2>
<pre><code class="language-bash">gpg --export --armor --output &lt;KEY.PUB&gt; &lt;KEY ID&gt;
gpg --import &lt;FILE&gt;
</code></pre>
<h2><a class="header" href="#search--send-keys" id="search--send-keys">Search &amp; Send keys</a></h2>
<pre><code class="language-bash">gpg --keyserver &lt;SERVER&gt; --send-keys &lt;KEY ID&gt;
gpg --keyserver &lt;SERVER&gt; --search-keys &lt;KEY ID&gt;
</code></pre>
<h2><a class="header" href="#encrypt-passphrase" id="encrypt-passphrase">Encrypt (passphrase)</a></h2>
<p>Encrypt file using <code>passphrase</code> and write encrypted data to <code>&lt;file&gt;.gpg</code>.</p>
<pre><code class="language-bash">gpg --symmetric &lt;file&gt;

# Decrypt using passphrase
gpg -o &lt;file&gt; --decrypt &lt;file&gt;.gpg
</code></pre>
<h2><a class="header" href="#encrypt-public-key" id="encrypt-public-key">Encrypt (public key)</a></h2>
<p>Encrypt file with <code>public key</code> of specified <code>recipient</code> and write encrypted
data to <code>&lt;file&gt;.gpg</code>.</p>
<pre><code class="language-bash">gpg --encrypt -r foo@bar.de &lt;file&gt;

# Decrypt at foos side (private key required)
gpg -o &lt;file&gt; --decrypt &lt;file&gt;.gpg
</code></pre>
<h2><a class="header" href="#signing" id="signing">Signing</a></h2>
<p>Generate a signed file and write to <code>&lt;file&gt;.gpg</code>.</p>
<pre><code class="language-bash">gpg --sign -u foor@bar.de &lt;file&gt;

# Verify
gpg --verify &lt;file&gt;

# Extract content from signed file
gpg -o &lt;file&gt; --decrypt &lt;file&gt;.gpg
</code></pre>
<blockquote>
<p>Without <code>-u</code> use first private key in list <code>gpg -K</code> for signing.</p>
</blockquote>
<p>Files can also be <code>signed</code> and <code>encrypted</code> at once, gpg will first sign the
file and then encrypt it.</p>
<pre><code class="language-bash">gpg --sign --encrypt &lt;file&gt;
</code></pre>
<h2><a class="header" href="#signing-detached" id="signing-detached">Signing (detached)</a></h2>
<p>Generate a <code>detached</code> signature and write to <code>&lt;file&gt;.asc</code>.
Send <code>&lt;file&gt;.asc</code> along with <code>&lt;file&gt;</code> when distributing.</p>
<pre><code class="language-bash">gpg --detach-sign --armor -u foor@bar.de &lt;file&gt;

# Verify
gpg --verify &lt;file&gt;.asc &lt;file&gt;
</code></pre>
<blockquote>
<p>Without <code>-u</code> use first private key in list <code>gpg -K</code> for signing.</p>
</blockquote>
<h2><a class="header" href="#abbreviations" id="abbreviations">Abbreviations</a></h2>
<ul>
<li><code>sec</code> secret key</li>
<li><code>ssb</code> secret subkey</li>
<li><code>pub</code> public key</li>
<li><code>sub</code> public subkey</li>
</ul>
<h2><a class="header" href="#keyservers" id="keyservers">Keyservers</a></h2>
<ul>
<li>http://pgp.mit.edu</li>
<li>http://keyserver.ubuntu.com</li>
<li>hkps://pgp.mailbox.org</li>
</ul>
<h1><a class="header" href="#gdb1" id="gdb1">gdb(1)</a></h1>
<h1><a class="header" href="#cli" id="cli">CLI</a></h1>
<pre><code class="language-markdown">  gdb [opts] [prg [-c coredump | -p pid]]
  gdb [opts] --args prg &lt;prg-args&gt;
    opts:
      -p &lt;pid&gt;        attach to pid
      -c &lt;coredump&gt;   use &lt;coredump&gt;
      -x &lt;file&gt;       execute script &lt;file&gt; before prompt
      -ex &lt;cmd&gt;       execute command &lt;cmd&gt; before prompt
      --tty &lt;tty&gt;     set I/O tty for debugee
</code></pre>
<h1><a class="header" href="#interactive-usage" id="interactive-usage">Interactive usage</a></h1>
<h2><a class="header" href="#misc" id="misc">Misc</a></h2>
<pre><code class="language-markdown">  tty &lt;tty&gt;
          Set &lt;tty&gt; as tty for debugee.
          Make sure nobody reads from target tty, easiest is to spawn a shell
          and run following in target tty:
          &gt; while true; do sleep 1024; done

  sharedlibrary [&lt;regex&gt;]
          Load symbols of shared libs loaded by debugee. Optionally use &lt;regex&gt;
          to filter libs for symbol loading.

  display [/FMT] &lt;expr&gt;
          Print &lt;expr&gt; every time debugee stops. Eg print next instr, see
          examples below.

  undisplay [&lt;num&gt;]
          Delete display expressions either all or one referenced by &lt;num&gt;.

  info display
          List display expressions.
</code></pre>
<h2><a class="header" href="#breakpoints" id="breakpoints">Breakpoints</a></h2>
<pre><code class="language-markdown">  break [-qualified] &lt;sym&gt; thread &lt;tnum&gt;
          Set a breakpoint only for a specific thread.
          -qualified: Treat &lt;sym&gt; as fully qualified symbol (quiet handy to set
          breakpoints on C symbols in C++ contexts)

  break &lt;sym&gt; if &lt;cond&gt;
          Set conditional breakpoint (see examples below).

  delete [&lt;num&gt;]
          Delete breakpoint either all or one referenced by &lt;num&gt;.

  info break
          List breakpoints.

  cond &lt;bp&gt; &lt;cond&gt;
          Make existing breakpoint &lt;bp&gt; conditional with &lt;cond&gt;.

  tbreak
          Set temporary breakpoint, will be deleted when hit.
          Same syntax as `break`.

  rbreak &lt;regex&gt;
          Set breakpoints matching &lt;regex&gt;, where matching internally is done
          on: .*&lt;regex&gt;.*

  command [&lt;bp_list&gt;]
          Define commands to run after breakpoint hit. If &lt;bp_list&gt; is not
          specified attach command to last created breakpoint. Command block
          terminated with 'end' token.

          &lt;bp_list&gt;: Space separates list, eg 'command 2 5-8' to run command
          for breakpoints: 2,5,6,7,8.
</code></pre>
<h2><a class="header" href="#inspection-1" id="inspection-1">Inspection</a></h2>
<pre><code class="language-markdown">  info functions [&lt;regex&gt;]
          List functions matching &lt;regex&gt;. List all functions if no &lt;regex&gt;
          provided.

  info variables [&lt;regex&gt;]
          List variables matching &lt;regex&gt;. List all variables if no &lt;regex&gt;
          provided.
</code></pre>
<h2><a class="header" href="#signal-handling" id="signal-handling">Signal handling</a></h2>
<pre><code class="language-markdown">  info handle [&lt;signal&gt;]
          Print how to handle &lt;signal&gt;. If no &lt;signal&gt; specified print for all
          signals.

  handle &lt;signal&gt; &lt;action&gt;
          Configure how gdb handles &lt;signal&gt; sent to debugee.
          &lt;action&gt;:
            stop/nostop       Catch signal in gdb and break.
            print/noprint     Print message when gdb catches signal.
            pass/nopass       Pass signal down to debugee.

  catch signal &lt;signal&gt;
          Create a catchpoint for &lt;signal&gt;.
</code></pre>
<h2><a class="header" href="#source-file-locations" id="source-file-locations">Source file locations</a></h2>
<pre><code class="language-markdown">  dir &lt;path&gt;
          Add &lt;path&gt; to the beginning of the searh path for source files.

  show dir
          Show current search path.

  set substitute-path &lt;from&gt; &lt;to&gt;
          Add substitution rule checked during source file lookup.

  show substitute-path
          Show current substitution rules.
</code></pre>
<h2><a class="header" href="#configuration" id="configuration">Configuration</a></h2>
<pre><code class="language-markdown">  set follow-fork-mode &lt;child | parent&gt;
          Specify which process to follow when debuggee makes a fork(2)
          syscall.

  set pagination &lt;on | off&gt;
          Turn on/off gdb's pagination.

  set breakpoint pending &lt;on | off | auto&gt;
          on: always set pending breakpoints.
          off: error when trying to set pending breakpoints.
          auto: interatively query user to set breakpoint.

  set print pretty &lt;on | off&gt;
          Turn on/off pertty printing of structures.

  set logging &lt;on | off&gt;
          Enable output logging to file (default gdb.txt).

  set logging file &lt;fname&gt;
          Change output log file to &lt;fname&gt;

  set logging redirect &lt;on/off&gt;
          on: only log to file.
          off: log to file and tty.
</code></pre>
<h1><a class="header" href="#user-commands-macros" id="user-commands-macros">User commands (macros)</a></h1>
<p>Gdb allows to create &amp; document user commands as follows:</p>
<pre><code class="language-markdown">  define &lt;cmd&gt;
    # cmds
  end

  document &lt;cmd&gt;
    # docu
  end
</code></pre>
<p>To get all user commands or documentations one can use:</p>
<pre><code class="language-markdown">  help user-defined
  help &lt;cmd&gt;
</code></pre>
<h1><a class="header" href="#hooks" id="hooks">Hooks</a></h1>
<p>Gdb allows to create two types of command <code>hooks</code></p>
<ul>
<li><code>hook-</code> will be run before <code>&lt;cmd&gt;</code></li>
<li><code>hookpost-</code> will be run after <code>&lt;cmd&gt;</code></li>
</ul>
<pre><code class="language-markdown">  define hook-&lt;cmd&gt;
    # cmds
  end

  define hookpost-&lt;cmd&gt;
    # cmds
  end
</code></pre>
<h1><a class="header" href="#examples-1" id="examples-1">Examples</a></h1>
<h2><a class="header" href="#automatically-print-next-instr" id="automatically-print-next-instr">Automatically print next instr</a></h2>
<p>When ever the debugee stops automatically print the memory at the current
instruction pointer (<code>$rip</code> x86) and format as instruction <code>/i</code>.</p>
<pre><code class="language-markdown">  # rip - x86
  display /i $rip

  # step instruction, after the step the next instruction is automatically printed
  si
</code></pre>
<h2><a class="header" href="#conditional-breakpoints" id="conditional-breakpoints">Conditional breakpoints</a></h2>
<p>Create conditional breakpoints for a function <code>void foo(int i)</code> in the debugee.</p>
<pre><code class="language-markdown">  # Create conditional breakpoint
  b foo if i == 42

  b foo     # would create bp 2
  # Make existing breakpoint conditional
  cond 2 if i == 7
</code></pre>
<h2><a class="header" href="#catch-sigsegv-and-execute-commands" id="catch-sigsegv-and-execute-commands">Catch SIGSEGV and execute commands</a></h2>
<p>This creates a <code>catchpoint</code> for the <code>SIGSEGV</code> signal and attached the <code>command</code>
to it.</p>
<pre><code class="language-markdown">  catch signal SIGSEGV
  command
    bt
    c
  end
</code></pre>
<h2><a class="header" href="#run-backtrace-on-thread-1-batch-mode" id="run-backtrace-on-thread-1-batch-mode">Run <code>backtrace</code> on thread 1 (batch mode)</a></h2>
<pre><code class="language-markdown">  gdb --batch -ex 'thread 1' -ex 'bt' -p &lt;pid&gt;
</code></pre>
<h2><a class="header" href="#script-gdb-for-automating-debugging-sessions" id="script-gdb-for-automating-debugging-sessions">Script gdb for automating debugging sessions</a></h2>
<p>To script gdb add commands into a file and pass it to gdb via <code>-x</code>.
For example create <code>run.gdb</code>:</p>
<pre><code class="language-markdown">  set pagination off

  break mmap
  command
    info reg rdi rsi rdx
    bt
    c
  end

  #initial drop
  c
</code></pre>
<p>This script can be used as:</p>
<pre><code class="language-markdown">  gdb --batch -x ./run.gdb -p &lt;pid&gt;
</code></pre>
<h1><a class="header" href="#know-bugs" id="know-bugs">Know Bugs</a></h1>
<h2><a class="header" href="#workaround-command--finish-bug" id="workaround-command--finish-bug">Workaround <code>command + finish</code> bug</a></h2>
<p>When using <code>finish</code> inside a <code>command</code> block, commands after <code>finish</code> are not
executed. To workaround that bug one can create a wrapper function which calls
<code>finish</code>.</p>
<pre><code class="language-markdown">  define handler
    bt
    finish
    info reg rax
  end

  command
    handler
  end
</code></pre>
<h1><a class="header" href="#radare21" id="radare21">radare2(1)</a></h1>
<h2><a class="header" href="#print" id="print">print</a></h2>
<pre><code class="language-markdown">
  pd &lt;n&gt; [@ &lt;addr&gt;]     # print disassembly for &lt;n&gt; instructions
                        # with optional temporary seek to &lt;addr&gt;
</code></pre>
<h2><a class="header" href="#flags" id="flags">flags</a></h2>
<pre><code class="language-markdown">  fs            # list flag-spaces
  fs &lt;fs&gt;       # select flag-space &lt;fs&gt;
  f             # print flags of selected flag-space
</code></pre>
<h2><a class="header" href="#help-1" id="help-1">help</a></h2>
<pre><code class="language-markdown">  ?*~&lt;kw&gt;       # '?*' list all commands and '~' grep for &lt;kw&gt;
  ?*~...        # '..' less mode /'...' interactive search
</code></pre>
<h2><a class="header" href="#relocation" id="relocation">relocation</a></h2>
<pre><code class="language-markdown">  &gt; r2 -B &lt;baddr&gt; &lt;exe&gt;         # open &lt;exe&gt; mapped to addr &lt;baddr&gt;
  oob &lt;addr&gt;                    # reopen current file at &lt;baddr&gt;
</code></pre>
<h1><a class="header" href="#qemu1" id="qemu1">qemu(1)</a></h1>
<p>All the examples &amp; notes use <code>qemu-system-x86_64</code> but in most cases
this can be swapped with the system emulator for other architectures.</p>
<h2><a class="header" href="#keybindings-1" id="keybindings-1">Keybindings</a></h2>
<pre><code class="language-markdown">Ctrl+Alt+g         release mouse capture from VM

Ctrl+Alt+1         switch to display of VM
Ctrl+Alt+2         switch to qemu monitor
</code></pre>
<h2><a class="header" href="#vm-config-snippet" id="vm-config-snippet">VM config snippet</a></h2>
<p>Following command-line gives a good starting point to assemble a VM:</p>
<pre><code class="language-bash">qemu-system-x86_64                              \
        -cpu host -enable-kvm -smp 4            \
        -m 8G                                   \
        -vga virtio -display sdl,gl=on          \
        -boot menu=on                           \
        -cdrom &lt;iso&gt;                            \
        -hda &lt;disk&gt;                             \
        -device qemu-xhci,id=xhci               \
        -device usb-host,bus=xhci.0,vendorid=0x05e1,productid=0x0408,id=capture-card
</code></pre>
<h3><a class="header" href="#cpu--ram" id="cpu--ram">CPU &amp; RAM</a></h3>
<ul>
<li><code>-cpu host</code> emulate host CPU in guest VM</li>
<li><code>-enable-kvm</code> use KVM instead software models (requires KVM on host machine)</li>
<li><code>-smp &lt;N&gt;</code> number of guest CPUs</li>
</ul>
<blockquote>
<p>List available CPUs <code>qemu-system-x86_64 -cpu help</code>.</p>
</blockquote>
<ul>
<li><code>-m 8G</code> size of guest RAM</li>
</ul>
<h3><a class="header" href="#graphic--display" id="graphic--display">Graphic &amp; Display</a></h3>
<ul>
<li><code>-vga virtio</code> use virtio as 3D video graphic accelerator (requires virgl in guest)</li>
<li><code>-display sdl,gl=on</code> use sdl window and enable openGL context</li>
</ul>
<h3><a class="header" href="#boot-menu" id="boot-menu">Boot Menu</a></h3>
<ul>
<li><code>-boot menu=on</code> enables boot menu to select boot device (enter with <code>ESC</code>)</li>
</ul>
<h3><a class="header" href="#block-devices" id="block-devices">Block devices</a></h3>
<ul>
<li><code>-cdrom &lt;iso&gt;</code> attach cdrom drive with iso to a VM</li>
<li><code>-hda &lt;disk&gt;</code> attach disk drive to a VM</li>
<li><code>-drive file=&lt;file&gt;,format=qcow2</code> generic way to configure &amp; attach a drive to a VM</li>
</ul>
<h4><a class="header" href="#create-a-disk-with-a-hrefhttpsqemureadthedocsioenlatesttoolsqemu-imghtmlqemu-imga" id="create-a-disk-with-a-hrefhttpsqemureadthedocsioenlatesttoolsqemu-imghtmlqemu-imga">Create a disk with <a href="https://qemu.readthedocs.io/en/latest/tools/qemu-img.html"><code>qemu-img</code></a></a></h4>
<p>To create a <code>qcow2</code> disk (qemu copy-on-write) of size <code>10G</code>:</p>
<pre><code class="language-bash">qemu-img create -f qcow2 disk.qcow2 10G
</code></pre>
<p>The disk does not contain any <code>partitions</code> or a <code>partition table</code>.
We can format the disk from <strong>within the <strong>guest</strong></strong> as following example:</p>
<pre><code class="language-bash"># Create `gpt` partition table.
sudo parted /dev/sda mktable gpt

# Create two equally sized primary partitions.
sudo parted /dev/sda mkpart primary 0% 50%
sudo parted /dev/sda mkpart primary 50% 100%

# Create filesystem on each partition.
sudo mkfs.ext3 /dev/sda1
sudo mkfs.ext4 /dev/sda2

lsblk -f /dev/sda
  NAME   FSTYPE LABEL UUID FSAVAIL FSUSE% MOUNTPOINT
  sda
  ├─sda1 ext3         ....
  └─sda2 ext4         ....
</code></pre>
<h3><a class="header" href="#usb" id="usb">USB</a></h3>
<h4><a class="header" href="#host-controller" id="host-controller">Host Controller</a></h4>
<ul>
<li><code>-device qemu-xhci,id=xhci</code> add XHCI USB controller to the VM (supports USB 3.0, 2.0, 1.1). <code>id=xhci</code> creates a usb bus named <code>xhci</code>.</li>
</ul>
<h4><a class="header" href="#usb-device" id="usb-device">USB Device</a></h4>
<ul>
<li><code>-device usb-host,bus=xhci.0,vendorid=0x05e1,productid=0x0408</code> pass-through USB device from host identified by vendorid &amp; productid and attach to usb bus <code>xhci.0</code> (defined with controller <code>id</code>)</li>
</ul>
<h2><a class="header" href="#references" id="references">References</a></h2>
<ul>
<li><a href="https://github.com/qemu/qemu/blob/master/docs/usb2.txt">QEMU USB</a></li>
<li><a href="https://qemu.readthedocs.io/en/latest/tools/qemu-img.html">QEMU IMG</a></li>
<li><a href="https://qemu.readthedocs.io/en/latest/tools/index.html">QEMU Tools</a></li>
<li><a href="https://www.qemu.org/docs/master/system/index.html">QEMU System</a></li>
</ul>
<h1><a class="header" href="#resource-analysis--monitor" id="resource-analysis--monitor">Resource analysis &amp; monitor</a></h1>
<ul>
<li><a href="monitor/./lsof.html">lsof</a></li>
<li><a href="monitor/./ss.html">ss</a></li>
<li><a href="monitor/./pidstat.html">pidstat</a></li>
<li><a href="monitor/./pgrep.html">pgrep</a></li>
<li><a href="monitor/./pmap.html">pmap</a></li>
<li><a href="monitor/./pstack.html">pstack</a></li>
</ul>
<h1><a class="header" href="#lsof8" id="lsof8">lsof(8)</a></h1>
<pre><code class="language-markdown">lsof
  -r &lt;s&gt; ..... repeatedly execute command ervery &lt;s&gt; seconds
  -a ......... AND slection filters instead ORing (OR: default)
  -p &lt;pid&gt; ... filter by &lt;pid&gt;
  +fg ........ show file flags for file descripros
  -n ......... don't convert network addr to hostnames
  -P ......... don't convert network port to service names
  -i &lt;@h[:p]&gt;. show connections to h (hostname|ip addr) with optional port p
  -s &lt;p:s&gt; ... in conjunction with '-i' filter for protocol &lt;p&gt; in state &lt;s&gt;
  -U ......... show unix domain sockets ('@' indicates abstract sock name, see unix(7))
</code></pre>
<pre><code class="language-markdown">file flags:
  R/W/RW ..... read/write/read-write
  CR ......... create
  AP ......... append
  TR ......... truncate
</code></pre>
<pre><code class="language-markdown">-s protocols
  TCP, UDP

-s states (TCP)
  CLOSED, IDLE, BOUND, LISTEN, ESTABLISHED, SYN_SENT, SYN_RCDV, ESTABLISHED,
  CLOSE_WAIT, FIN_WAIT1, CLOSING, LAST_ACK, FIN_WAIT_2, TIME_WAIT

-s states (UDP)
  Unbound, Idle
</code></pre>
<h1><a class="header" href="#examples-2" id="examples-2">Examples</a></h1>
<h2><a class="header" href="#file-flags" id="file-flags">File flags</a></h2>
<p>Show open files with file flags for process:</p>
<pre><code class="language-markdown">lsof +fg -p &lt;pid&gt;
</code></pre>
<h2><a class="header" href="#open-tcp-connections" id="open-tcp-connections">Open TCP connections</a></h2>
<p>Show open tcp connections for <code>$USER</code>:</p>
<pre><code class="language-markdown">lsof -a -u $USER -i TCP
</code></pre>
<p><strong>Note</strong>: <code>-a</code> <em>ands</em> the results. If <code>-a</code> is not given all open files matching
<code>$USER</code> and all tcp connections are listed (<em>ored</em>).</p>
<h2><a class="header" href="#open-connection-to-specific-host" id="open-connection-to-specific-host">Open connection to specific host</a></h2>
<p>Show open connections to <code>localhost</code> for <code>$USER</code>:</p>
<pre><code class="language-markdown">lsof -a -u $USER -i @localhost
</code></pre>
<h2><a class="header" href="#open-connection-to-specific-port" id="open-connection-to-specific-port">Open connection to specific port</a></h2>
<p>Show open connections to port <code>:1234</code> for <code>$USER</code>:</p>
<pre><code class="language-markdown">lsof -a -u $USER -i :1234
</code></pre>
<h2><a class="header" href="#ipv4-tcp-connections-in-established-state" id="ipv4-tcp-connections-in-established-state">IPv4 TCP connections in <code>ESTABLISHED</code> state</a></h2>
<pre><code class="language-markdown">lsof -i 4TCP -s TCP:ESTABLISHED
</code></pre>
<h1><a class="header" href="#ss8" id="ss8">ss(8)</a></h1>
<pre><code class="language-markdown">ss [option] [filter]
</code></pre>
<pre><code class="language-markdown">[option]
  -p ..... Show process using socket
  -l ..... Show sockets in listening state
  -4/-6 .. Show IPv4/6 sockets
  -x ..... Show unix sockets
  -n ..... Show numeric ports (no resolve)
  -O ..... Oneline output per socket
</code></pre>
<pre><code class="language-markdown">[filter]
  dport/sport PORT .... Filter for destination/source port
  dst/src ADDR ........ Filter for destination/source address

  and/or .............. Logic operator
  ==/!= ............... Comparison operator

  (EXPR) .............. Group exprs
</code></pre>
<h1><a class="header" href="#examples-3" id="examples-3">Examples</a></h1>
<p>Show all tcp IPv4 sockets connecting to port <code>443</code>:</p>
<pre><code class="language-markdown">ss -4 'dport 443'
</code></pre>
<p>Show all tcp IPv4 sockets that don't connect to port <code>443</code> or connect to address <code>1.2.3.4</code>.</p>
<pre><code class="language-markdown">ss -4 'dport != 443 or dst 1.2.3.4'
</code></pre>
<h1><a class="header" href="#pidstat1" id="pidstat1">pidstat(1)</a></h1>
<pre><code class="language-markdown">pidstat [opt] [interval] [cont]
  -U [user]     show username instead UID, optionally only show for user
  -r            memory statistics
  -d            I/O statistics
  -h            single line per process and no lines with average
</code></pre>
<h1><a class="header" href="#page-fault-and-memory-utilization" id="page-fault-and-memory-utilization">Page fault and memory utilization</a></h1>
<pre><code class="language-markdown">pidstat -r -p &lt;pid&gt; [interval] [count]
</code></pre>
<pre><code class="language-markdown">minor_pagefault: Happens when the page needed is already in memory but not
                 allocated to the faulting process, in that case the kernel
                 only has to create a new page-table entry pointing to the
                 shared physical page (not required to load a memory page from
                 disk).

major_pagefault: Happens when the page needed is NOT in memory, the kernel
                 has to create a new page-table entry and populate the
                 physical page (required to load a memory page from disk).
</code></pre>
<h1><a class="header" href="#io-statistics" id="io-statistics">I/O statistics</a></h1>
<pre><code class="language-markdown">pidstat -d -p &lt;pid&gt; [interval] [count]
</code></pre>
<h1><a class="header" href="#pgrep1" id="pgrep1">pgrep(1)</a></h1>
<pre><code class="language-markdown">pgrep [opts] &lt;pattern&gt;
  -n         only list newest matching process
  -u &lt;usr&gt;   only show matching for user &lt;usr&gt;
  -l         additionally list command
  -a         additionally list command + arguments
</code></pre>
<h2><a class="header" href="#debug-newest-process" id="debug-newest-process">Debug newest process</a></h2>
<p>For example attach gdb to newest zsh process from <code>$USER</code>.</p>
<pre><code class="language-markdown">gdb -p $(pgrep -n -u $USER zsh)
</code></pre>
<h1><a class="header" href="#pmap1" id="pmap1">pmap(1)</a></h1>
<pre><code class="language-markdown">pmap &lt;pid&gt;
    Dump virtual memory map of process.
    Compared to /proc/&lt;pid&gt;/maps it shows the size of the mappings.
</code></pre>
<h1><a class="header" href="#pstack1" id="pstack1">pstack(1)</a></h1>
<pre><code class="language-markdown">pstack &lt;pid&gt;
    Dump stack for all threads of process.
</code></pre>
<h1><a class="header" href="#trace-and-profile" id="trace-and-profile">Trace and Profile</a></h1>
<ul>
<li><a href="trace_profile/./strace.html">strace</a></li>
<li><a href="trace_profile/./ltrace.html">ltrace</a></li>
<li><a href="trace_profile/./perf.html">perf</a></li>
<li><a href="trace_profile/./oprofile.html">OProfile</a></li>
<li><a href="trace_profile/./time.html">time</a></li>
</ul>
<h1><a class="header" href="#strace1" id="strace1">strace(1)</a></h1>
<pre><code class="language-markdown">strace [opts] [prg]
  -f .......... follow child processes on fork(2)
  -p &lt;pid&gt; .... attach to running process
  -s &lt;size&gt; ... max string size, truncate of longer (default: 32)
  -e &lt;expr&gt; ... expression for trace filtering
  -o &lt;file&gt; ... log output into &lt;file&gt;
  -c .......... dump syscall statitics at the end
</code></pre>
<pre><code class="language-markdown">&lt;expr&gt;:
  trace=syscall[,syscall] .... trace only syscall listed
  trace=file ................. trace all syscall that take a filename as arg
  trace=process .............. trace process management related syscalls
  trace=signal ............... trace signal related syscalls
  signal ..................... trace signals delivered to the process
</code></pre>
<h1><a class="header" href="#examples-4" id="examples-4">Examples</a></h1>
<p>Trace <code>open(2)</code> &amp; <code>socket(2)</code> syscalls for a running process + child processes:</p>
<pre><code class="language-markdown">strace -f -e trace=open,socket -p &lt;pid&gt;
</code></pre>
<p>Trace signals delivered to a running process:</p>
<pre><code class="language-markdown">strace -f -e signal -p &lt;pid&gt;
</code></pre>
<h1><a class="header" href="#ltrace1" id="ltrace1">ltrace(1)</a></h1>
<pre><code class="language-markdown">ltrace [opts] [prg]
  -f .......... follow child processes on fork(2)
  -p &lt;pid&gt; .... attach to running process
  -o &lt;file&gt; ... log output into &lt;file&gt;
  -l &lt;filter&gt; . show who calls into lib matched by &lt;filter&gt;
  -C .......... demangle
</code></pre>
<h1><a class="header" href="#example-4" id="example-4">Example</a></h1>
<p>List which program/libs call into <code>libstdc++</code>:</p>
<pre><code class="language-bash">ltrace -l '*libstdc++*' -C -o ltrace.log ./main
</code></pre>
<h1><a class="header" href="#perf1" id="perf1">perf(1)</a></h1>
<pre><code class="language-markdown">perf list      show supported hw/sw events

perf stat
  -p &lt;pid&gt; .. show stats for running process
  -I &lt;ms&gt; ... show stats periodically over interval &lt;ms&gt;
  -e &lt;ev&gt; ... filter for events

perf top
  -p &lt;pid&gt; .. show stats for running process
  -F &lt;hz&gt; ... sampling frequency
  -K ........ hide kernel threads

perf record
  -p &lt;pid&gt; ............... record stats for running process
  -F &lt;hz&gt; ................ sampling frequency
  --call-graph &lt;method&gt; .. [fp, dwarf, lbr] method how to caputre backtrace
                           fp   : use frame-pointer, need to compile with
                                  -fno-omit-frame-pointer
                           dwarf: use .cfi debug information
                           lbr  : use hardware last branch record facility
  -g ..................... short-hand for --call-graph fp
  -e &lt;ev&gt; ................ filter for events

perf report
  -n .................... annotate symbols with nr of samples
  --stdio ............... report to stdio, if not presen tui mode
  -g graph,0.5,caller ... show caller based call chains with value &gt;0.5
</code></pre>
<pre><code class="language-markdown">Useful &lt;ev&gt;:
  page-faults
  minor-faults
  major-faults
  cpu-cycles`
  task-clock
</code></pre>
<h2><a class="header" href="#a-hrefhttpsgithubcombrendangreggflamegraphflamegrapha" id="a-hrefhttpsgithubcombrendangreggflamegraphflamegrapha"><a href="https://github.com/brendangregg/FlameGraph"><code>Flamegraph</code></a></a></h2>
<h3><a class="header" href="#flamegraph-with-single-event-trace" id="flamegraph-with-single-event-trace">Flamegraph with single event trace</a></h3>
<pre><code class="language-markdown">perf record -g -e cpu-cycles -p &lt;pid&gt;
perf script | FlameGraph/stackcollapse-perf.pl | FlameGraph/flamegraph.pl &gt; cycles-flamegraph.svg
</code></pre>
<h3><a class="header" href="#flamegraph-with-multiple-event-traces" id="flamegraph-with-multiple-event-traces">Flamegraph with multiple event traces</a></h3>
<pre><code class="language-markdown">perf record -g -e cpu-cycles,page-faults -p &lt;pid&gt;
perf script --per-event-dump
# fold &amp; generate as above
</code></pre>
<h1><a class="header" href="#a-hrefhttpsoprofilesourceforgeiooprofilea" id="a-hrefhttpsoprofilesourceforgeiooprofilea"><a href="https://oprofile.sourceforge.io/">OProfile</a></a></h1>
<pre><code class="language-markdown">operf -g -p &lt;pid&gt;
  -g ...... caputre call-graph information

opreport [opt] FILE
            show time spent per binary image
  -l ...... show time spent per symbol
  -c ...... show callgraph information (see below)
  -a ...... add column with time spent accumulated over child nodes

ophelp      show supported hw/sw events
</code></pre>
<h1><a class="header" href="#usrbintime1" id="usrbintime1">/usr/bin/time(1)</a></h1>
<pre><code class="language-markdown"># statistics of process run
/usr/bin/time -v &lt;cmd&gt;
</code></pre>
<h1><a class="header" href="#binary" id="binary">Binary</a></h1>
<ul>
<li><a href="binary/./od.html">od</a></li>
<li><a href="binary/./xxd.html">xxd</a></li>
<li><a href="binary/./readelf.html">readelf</a></li>
<li><a href="binary/./objdump.html">objdump</a></li>
<li><a href="binary/./nm.html">nm</a></li>
</ul>
<h1><a class="header" href="#od1" id="od1">od(1)</a></h1>
<pre><code class="language-markdown">  od [opts] &lt;file&gt;
    -An         don't print addr info
    -tx4        print hex in 4 byte chunks
    -ta         print as named character
    -tc         printable chars or backslash escape
    -w4         print 4 bytes per line
    -j &lt;n&gt;      skip &lt;n&gt; bytes from &lt;file&gt; (hex if start with 0x)
    -N &lt;n&gt;      dump &lt;n&gt; bytes (hex of start with 0x)
</code></pre>
<h2><a class="header" href="#ascii-to-hex-string" id="ascii-to-hex-string">ASCII to hex string</a></h2>
<pre><code class="language-markdown">  echo -n AAAABBBB | od -An -w4 -tx4
    &gt;&gt; 41414141
    &gt;&gt; 42424242

  echo -n '\x7fELF\n' | od -tx1 -ta -tc
    &gt;&gt; 0000000  7f  45  4c  46  0a      # tx1
    &gt;&gt;         del   E   L   F  nl      # ta
    &gt;&gt;         177   E   L   F  \n      # tc
</code></pre>
<h2><a class="header" href="#extract-parts-of-file" id="extract-parts-of-file">Extract parts of file</a></h2>
<p>For example <code>.rodata</code> section from an elf file. We can use <code>readelf</code> to get the
offset into the file where the <code>.rodata</code> section starts.</p>
<pre><code class="language-markdown">  readelf -W -S foo
    &gt;&gt; Section Headers:
    &gt;&gt; [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
    &gt;&gt; ...
    &gt;&gt; [15] .rodata           PROGBITS        00000000004009c0 0009c0 000030 00   A  0   0 16
</code></pre>
<p>With the offset of <code>-j 0x0009c0</code> we can dump <code>-N 0x30</code> bytes from the beginning of
the <code>.rodata</code> section as follows:</p>
<pre><code class="language-markdown">  od -j 0x0009c0 -N 0x30 -tx4 -w4 foo
    &gt;&gt; 0004700 00020001
    &gt;&gt; 0004704 00000000
    &gt;&gt; *
    &gt;&gt; 0004740 00000001
    &gt;&gt; 0004744 00000002
    &gt;&gt; 0004750 00000003
    &gt;&gt; 0004754 00000004
</code></pre>
<p><strong>Note</strong>: Numbers starting with <code>0x</code> will be interpreted as hex by <code>od</code>.</p>
<h1><a class="header" href="#xxd1" id="xxd1">xxd(1)</a></h1>
<pre><code class="language-markdown">  xxd [opts]
    -p          dump continuous hexdump
    -r          convert hexdump into binary ('revert')
    -e          dump as little endian mode
    -i          output as C array
</code></pre>
<h2><a class="header" href="#ascii-to-hex-stream" id="ascii-to-hex-stream">ASCII to hex stream</a></h2>
<pre><code class="language-markdown">  echo -n 'aabb' | xxd -p
    &gt;&gt; 61616262
</code></pre>
<h2><a class="header" href="#hex-to-binary-stream" id="hex-to-binary-stream">Hex to binary stream</a></h2>
<pre><code class="language-markdown">  echo -n '61616262' | xxd -p -r
    &gt;&gt; aabb
</code></pre>
<h2><a class="header" href="#ascii-to-binary" id="ascii-to-binary">ASCII to binary</a></h2>
<pre><code class="language-markdown">  echo -n '\x7fELF' | xxd -p | xxd -p -r | file -p -
    &gt;&gt; ELF
</code></pre>
<h2><a class="header" href="#ascii-to-c-array-hex-encoded" id="ascii-to-c-array-hex-encoded">ASCII to <code>C</code> array (hex encoded)</a></h2>
<pre><code class="language-markdown">  xxd -i &lt;(echo -n '\x7fELF')
    &gt;&gt; unsigned char _proc_self_fd_11[] = {
    &gt;&gt;   0x7f, 0x45, 0x4c, 0x46
    &gt;&gt; };
    &gt;&gt; unsigned int _proc_self_fd_11_len = 4;
</code></pre>
<h1><a class="header" href="#readelf1" id="readelf1">readelf(1)</a></h1>
<pre><code class="language-markdown">  readelf [opts] &lt;elf&gt;
    -W|--wide     wide output, dont break output at 80 chars
    -h            print ELF header
    -S            print section headers
    -l            print program headers + segment mapping
    -d            print .dynamic section (dynamic link information)
    --syms        print symbol tables (.symtab .dynsym)
    --dyn-syms    print dynamic symbol table (exported symbols for dynamic linker)
    -r            print relocation sections (.rel.*, .rela.*)
</code></pre>
<h1><a class="header" href="#objdump1" id="objdump1">objdump(1)</a></h1>
<pre><code class="language-markdown">  objdump [opts] &lt;elf&gt;
    -M intel                use intil syntax
    -d                      disassemble text section
    -D                      disassemble all sections
    -S                      mix disassembly with source code
    -C                      demangle
    -j &lt;section&gt;            display info for section
    --[no-]show-raw-insn    [dont] show object code next to disassembly
</code></pre>
<h2><a class="header" href="#disassemble-section" id="disassemble-section">Disassemble section</a></h2>
<p>For example <code>.plt</code> section:</p>
<pre><code class="language-markdown">  objdump -j .plt -d &lt;elf&gt;
</code></pre>
<h1><a class="header" href="#nm1" id="nm1">nm(1)</a></h1>
<pre><code class="language-markdown">  nm [opts] &lt;elf&gt;
    -C          demangle
    -u          undefined only
</code></pre>
<h1><a class="header" href="#development" id="development">Development</a></h1>
<ul>
<li><a href="development/./c++filt.html">c++filt</a></li>
<li><a href="development/./c++.html">c++</a></li>
<li><a href="development/./glibc.html">glibc</a></li>
<li><a href="development/./gcc.html">gcc</a></li>
<li>[make] (./make.md)</li>
<li><a href="development/./ld.so.html">ld.so</a></li>
</ul>
<h1><a class="header" href="#cfilt1" id="cfilt1">c++filt(1)</a></h1>
<h2><a class="header" href="#demangle-symbol" id="demangle-symbol">Demangle symbol</a></h2>
<pre><code class="language-markdown">  c++-filt &lt;symbol_str&gt;
</code></pre>
<h2><a class="header" href="#demangle-stream" id="demangle-stream">Demangle stream</a></h2>
<p>For example dynamic symbol table:</p>
<pre><code class="language-markdown">  readelf -W --dyn-syms &lt;elf&gt; | c++filt
</code></pre>
<h1><a class="header" href="#c" id="c">c++</a></h1>
<h2><a class="header" href="#type-deduction" id="type-deduction">Type deduction</a></h2>
<p>Force compile error to see what <code>auto</code> is deduced to.</p>
<pre><code class="language-cpp">auto foo = bar();

// force compile error
typename decltype(foo)::_;
</code></pre>
<h1><a class="header" href="#glibc" id="glibc">glibc</a></h1>
<h2><a class="header" href="#malloc-tracer-a-hrefhttpman7orglinuxman-pagesman3mtrace3htmlmtrace3a" id="malloc-tracer-a-hrefhttpman7orglinuxman-pagesman3mtrace3htmlmtrace3a">malloc tracer <a href="http://man7.org/linux/man-pages/man3/mtrace.3.html"><code>mtrace(3)</code></a></a></h2>
<p>Trace memory allocation and de-allocation to detect memory leaks.
Need to call <code>mtrace(3)</code> to install the tracing hooks.</p>
<p>If we can't modify the binary to call <code>mtrace</code> we can create a small shared
library and pre-load it.</p>
<pre><code class="language-c">// libmtrace.c
#include &lt;mcheck.h&gt;
__attribute__((constructor))  static void init_mtrace() { mtrace(); }
</code></pre>
<p>Compile as:</p>
<pre><code class="language-bash">gcc -shared -fPIC -o libmtrace.so libmtrace.c
</code></pre>
<p>To generate the trace file run:</p>
<pre><code class="language-bash">export MALLOC_TRACE=&lt;file&gt;
LD_PRELOAD=./libmtrace.so &lt;binary&gt;
</code></pre>
<p><strong>Note</strong>: If <code>MALLOC_TRACE</code> is not set <code>mtrace</code> won't install tracing hooks.</p>
<p>To get the results of the trace file:</p>
<pre><code class="language-bash">mtrace &lt;binary&gt; $MALLOC_TRACE
</code></pre>
<h2><a class="header" href="#malloc-check-a-hrefhttpman7orglinuxman-pagesman3mallopt3htmlmallopt3a" id="malloc-check-a-hrefhttpman7orglinuxman-pagesman3mallopt3htmlmallopt3a">malloc check <a href="http://man7.org/linux/man-pages/man3/mallopt.3.html"><code>mallopt(3)</code></a></a></h2>
<p>Configure action when glibc detects memory error.</p>
<pre><code class="language-bash">export MALLOC_CHECK_=&lt;N&gt;
</code></pre>
<p>Useful values:</p>
<pre><code class="language-markdown">1   print detailed error &amp; continue
3   print detailed error + stack trace + memory mappings &amp; abort
7   print simple error message + stack trace + memory mappings &amp; abort
</code></pre>
<h1><a class="header" href="#gcc1" id="gcc1">gcc(1)</a></h1>
<h2><a class="header" href="#cli-1" id="cli-1">CLI</a></h2>
<h3><a class="header" href="#preprocessing" id="preprocessing">Preprocessing</a></h3>
<p>While debugging can be helpful to just pre-process files.</p>
<pre><code class="language-bash">gcc -E [-dM] ...
</code></pre>
<ul>
<li><code>-E</code> run only preprocessor</li>
<li><code>-dM</code> list only <code>#define</code> statements</li>
</ul>
<h2><a class="header" href="#a-hrefhttpsgccgnuorgonlinedocsgccother-builtinshtmlbuiltinsa" id="a-hrefhttpsgccgnuorgonlinedocsgccother-builtinshtmlbuiltinsa"><a href="https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html">Builtins</a></a></h2>
<h3><a class="header" href="#__builtin_expectexpr-cond" id="__builtin_expectexpr-cond"><code>__builtin_expect(expr, cond)</code></a></h3>
<p>Give the compiler a hint which branch is hot, so it can lay out the code
accordingly to reduce number of jump instructions.
See on <a href="https://godbolt.org/z/MbTHAP">compiler explorer</a>.</p>
<pre><code class="language-bash">echo &quot;
extern void foo();
extern void bar();
void run0(int x) {
  if (__builtin_expect(x,0)) { foo(); }
  else { bar(); }
}
void run1(int x) {
  if (__builtin_expect(x,1)) { foo(); }
  else { bar(); }
}
&quot; | gcc -O2 -S -masm=intel -o /dev/stdout -xc -
</code></pre>
<p>Will generate something similar to the following.</p>
<ul>
<li><code>run0</code>: <code>bar</code> is on the path without branch</li>
<li><code>run1</code>: <code>foo</code> is on the path without branch</li>
</ul>
<pre><code class="language-x86asm">run0:
        test    edi, edi
        jne     .L4
        xor     eax, eax
        jmp     bar
.L4:
        xor     eax, eax
        jmp     foo
run1:
        test    edi, edi
        je      .L6
        xor     eax, eax
        jmp     foo
.L6:
        xor     eax, eax
        jmp     bar
</code></pre>
<h2><a class="header" href="#abi-linux" id="abi-linux">ABI (Linux)</a></h2>
<ul>
<li>C ABI - <a href="https://www.uclibc.org/docs/psABI-x86_64.pdf">SystemV ABI</a></li>
<li>C++ ABI - <a href="https://itanium-cxx-abi.github.io/cxx-abi">C++ Itanium ABI</a></li>
</ul>
<h1><a class="header" href="#make1" id="make1">make(1)</a></h1>
<h2><a class="header" href="#anatomy-of-make-rules" id="anatomy-of-make-rules">Anatomy of <code>make</code> rules</a></h2>
<pre><code class="language-make">target .. : prerequisite ..
	recipe
	..
</code></pre>
<ul>
<li><code>target</code>: an output generated by the rule</li>
<li><code>prerequisite</code>: an input that is used to generate the target</li>
<li><code>recipe</code>: list of actions to generate the output from the input</li>
</ul>
<blockquote>
<p>Use <code>make -p</code> to print all rules and variables (implicitly + explicitly defined).</p>
</blockquote>
<h2><a class="header" href="#pattern-rules--automatic-variables" id="pattern-rules--automatic-variables">Pattern rules &amp; Automatic variables</a></h2>
<h3><a class="header" href="#pattern-rules" id="pattern-rules">Pattern rules</a></h3>
<p>A pattern rule contains the <code>%</code> char (exactly one of them) and look like this example:</p>
<pre><code class="language-make">%.o : %.c
	$(CC) -c $(CFLAGS) $(CPPFLAGS) $&lt; -o $@
</code></pre>
<p>The target matches files of the pattern <code>%.o</code>, where <code>%</code> matches any none-empty
substring and other character match just them self.</p>
<p>The substring matched by <code>%</code> is called the <code>stem</code>.</p>
<p><code>%</code> in the prerequisite stands for the matched <code>stem</code> in the target.</p>
<h3><a class="header" href="#automatic-variables" id="automatic-variables">Automatic variables</a></h3>
<p>As targets and prerequisites in pattern rules can't be spelled explicitly in
the recipe, make provides a set of automatic variables to work with:</p>
<ul>
<li><code>$@</code>: Name of the target that triggered the rule.</li>
<li><code>$&lt;</code>: Name of the first prerequisite.</li>
<li><code>$^</code>: Names of all prerequisites (without duplicates).</li>
<li><code>$+</code>: Names of all prerequisites (with duplicates).</li>
<li><code>$*</code>: Stem of the pattern rule.</li>
</ul>
<pre><code class="language-make"># file: Makefile

all: foobar blabla

foo% bla%: aaa bbb bbb
	@echo &quot;@ = $@&quot;
	@echo &quot;&lt; = $&lt;&quot;
	@echo &quot;^ = $^&quot;
	@echo &quot;+ = $+&quot;
	@echo &quot;* = $*&quot;
	@echo &quot;----&quot;

aaa:
bbb:
</code></pre>
<p>Running above <code>Makefile</code> gives:</p>
<pre><code class="language-test">@ = foobar
&lt; = aaa
^ = aaa bbb
+ = aaa bbb bbb
* = bar
----
@ = blabla
&lt; = aaa
^ = aaa bbb
+ = aaa bbb bbb
* = bla
----
</code></pre>
<h2><a class="header" href="#useful-functions" id="useful-functions">Useful functions</a></h2>
<h3><a class="header" href="#substitution-references" id="substitution-references">Substitution references</a></h3>
<p>Substitute strings matching pattern in a list.</p>
<pre><code class="language-make">in  := a.o l.a c.o
out := $(in:.o=.c)
# =&gt; out = a.c l.a c.c
</code></pre>
<h3><a class="header" href="#filter" id="filter"><code>filter</code></a></h3>
<p>Keep strings matching a pattern in a list.</p>
<pre><code class="language-make">in  := a.a b.b c.c d.d
out := $(filter %.b %.c, $(in))
# =&gt; out = b.b c.c
</code></pre>
<h3><a class="header" href="#filter-out" id="filter-out"><code>filter-out</code></a></h3>
<p>Remove strings matching a pattern from a list.</p>
<pre><code class="language-make">in  := a.a b.b c.c d.d
out := $(filter-out %.b %.c, $(in))
# =&gt; out = a.a d.d
</code></pre>
<h3><a class="header" href="#abspath" id="abspath"><code>abspath</code></a></h3>
<p>Resolve each file name as absolute path (don't resolve symlinks).</p>
<pre><code class="language-make">$(abspath fname1 fname2 ..)

### `realpath`
Resolve each file name as canonical path.
```make
$(realpath fname1 fname2 ..)
</code></pre>
<h1><a class="header" href="#ldso8" id="ldso8">ld.so(8)</a></h1>
<h2><a class="header" href="#environment-variables" id="environment-variables">Environment Variables</a></h2>
<pre><code class="language-console">  LD_PRELOAD=&lt;l_so&gt;       colon separated list of libso's to be pre loaded
  LD_DEBUG=&lt;opts&gt;         comma separated list of debug options
          =help           list available options
          =libs           show library search path
          =files          processing of input files
          =symbols        show search path for symbol lookup
          =bindings       show against which definition a symbol is bound
</code></pre>
<h2><a class="header" href="#ld_preload-initialization-order-and-link-map" id="ld_preload-initialization-order-and-link-map">LD_PRELOAD: Initialization Order and Link Map</a></h2>
<p>Libraries specified in <code>LD_PRELOAD</code> are loaded from <code>left-to-right</code> but
initialized from <code>right-to-left</code>.</p>
<pre><code class="language-markdown">  &gt; ldd ./main
    &gt;&gt; libc.so.6 =&gt; /usr/lib/libc.so.6

  &gt; LD_PRELOAD=liba.so:libb.so ./main
             --&gt;
      preloaded in this order
             &lt;--
      initialized in this order
</code></pre>
<p>The preload order determines:</p>
<ul>
<li>the order libraries are inserted into the <code>link map</code></li>
<li>the initialization order for libraries</li>
</ul>
<p>For the example listed above the resulting <code>link map</code> will look like the
following:</p>
<pre><code class="language-makrdown">  +------+    +------+    +------+    +------+
  | main | -&gt; | liba | -&gt; | libb | -&gt; | libc |
  +------+    +------+    +------+    +------+
</code></pre>
<p>This can be seen when running with <code>LD_DEBUG=files</code>:</p>
<pre><code class="language-makrdown">  &gt; LD_DEBUG=files LD_PRELOAD=liba.so:libb.so ./main
    # load order (-&gt; determines link map)
    &gt;&gt; file=liba.so [0];  generating link map
    &gt;&gt; file=libb.so [0];  generating link map
    &gt;&gt; file=libc.so.6 [0];  generating link map

    # init order
    &gt;&gt; calling init: /usr/lib/libc.so.6
    &gt;&gt; calling init: &lt;path&gt;/libb.so
    &gt;&gt; calling init: &lt;path&gt;/liba.so
    &gt;&gt; initialize program: ./main
</code></pre>
<p>To verify the <code>link map</code> order we let <code>ld.so</code> resolve the <code>memcpy(3)</code> libc
symbol (used in <em>main</em>) dynamically, while enabling <code>LD_DEBUG=symbols,bindings</code>
to see the resolving in action.</p>
<pre><code class="language-makrdown">  &gt; LD_DEBUG=symbols,bindings LD_PRELOAD=liba.so:libb.so ./main
    &gt;&gt; symbol=memcpy;  lookup in file=./main [0]
    &gt;&gt; symbol=memcpy;  lookup in file=&lt;path&gt;/liba.so [0]
    &gt;&gt; symbol=memcpy;  lookup in file=&lt;path&gt;/libb.so [0]
    &gt;&gt; symbol=memcpy;  lookup in file=/usr/lib/libc.so.6 [0]
    &gt;&gt; binding file ./main [0] to /usr/lib/libc.so.6 [0]: normal symbol `memcpy' [GLIBC_2.14]
</code></pre>
<h2><a class="header" href="#dynamic-linking-x86_64" id="dynamic-linking-x86_64">Dynamic Linking (x86_64)</a></h2>
<p>Dynamic linking basically works via one indirect jump. It uses a combination of
function trampolines (<code>.plt</code> section) and a function pointer table (<code>.got.plt</code>
section).
On the first call the trampoline sets up some metadata and then jumps to the
<code>ld.so</code> runtime resolve function, which in turn patches the table with the
correct function pointer.</p>
<pre><code class="language-makrdown">  .plt ....... procedure linkage table, contains function trampolines, usually
               located in code segment (rx permission)
  .got.plt ... global offset table for .plt, holds the function pointer table
</code></pre>
<p>Using <code>radare2</code> we can analyze this in more detail:</p>
<pre><code class="language-makrdown">  [0x00401040]&gt; pd 4 @ section..got.plt
              ;-- section..got.plt:
              ;-- .got.plt:    ; [22] -rw- section size 32 named .got.plt
              ;-- _GLOBAL_OFFSET_TABLE_:
         [0]  0x00404000      .qword 0x0000000000403e10 ; section..dynamic
         [1]  0x00404008      .qword 0x0000000000000000
              ; CODE XREF from section..plt @ +0x6
         [2]  0x00404010      .qword 0x0000000000000000
              ;-- reloc.puts:
              ; CODE XREF from sym.imp.puts @ 0x401030
         [3]  0x00404018      .qword 0x0000000000401036 ; RELOC 64 puts

  [0x00401040]&gt; pd 6 @ section..plt
              ;-- section..plt:
              ;-- .plt:       ; [12] -r-x section size 32 named .plt
          ┌─&gt; 0x00401020      ff35e22f0000   push qword [0x00404008]
          â•Ž   0x00401026      ff25e42f0000   jmp qword [0x00404010]
          â•Ž   0x0040102c      0f1f4000       nop dword [rax]
  ┌ 6: int sym.imp.puts (const char *s);
  â””       â•Ž   0x00401030      ff25e22f0000   jmp qword [reloc.puts]
          â•Ž   0x00401036      6800000000     push 0
          └─&lt; 0x0040103b      e9e0ffffff     jmp sym..plt
</code></pre>
<ul>
<li>At address <code>0x00401030</code> in the <code>.plt</code> section we see the indirect jump for
<code>puts</code> using the function pointer in <code>_GLOBAL_OFFSET_TABLE_[3] (GOT)</code>.</li>
<li><code>GOT[3]</code> initially points to instruction after the <code>puts</code> trampoline
<code>0x00401036</code>.</li>
<li>This pushes the relocation index <code>0</code> and then jumps to the first trampoline
<code>0x00401020</code>.</li>
<li>The first trampoline jumps to <code>GOT[2]</code> which will be filled at program
startup by the <code>ld.so</code> with its resolve function.</li>
<li>The <code>ld.so</code> resolve function fixes the relocation referenced by the
relocation index pushed by the <code>puts</code> trampoline.</li>
<li>The relocation entry at index <code>0</code> tells the resolve function which symbol to
search for and where to put the function pointer:
<pre><code class="language-makrdown">  &gt; readelf -r &lt;main&gt;
    &gt;&gt; Relocation section '.rela.plt' at offset 0x4b8 contains 1 entry:
    &gt;&gt;   Offset          Info           Type           Sym. Value    Sym. Name + Addend
    &gt;&gt; 000000404018  000200000007 R_X86_64_JUMP_SLO 0000000000000000 puts@GLIBC_2.2.5 + 0
</code></pre>
As we can see the offset from relocation at index <code>0</code> points to <code>GOT[3]</code>.</li>
</ul>
<h1><a class="header" href="#arch" id="arch">Arch</a></h1>
<ul>
<li><a href="arch/./x86_64.html">x86_64</a></li>
<li><a href="arch/./arm64.html">arm64</a></li>
<li><a href="arch/./armv7.html">armv7</a></li>
</ul>
<h1><a class="header" href="#x86_64" id="x86_64">x86_64</a></h1>
<p>keywords: x86_64, x86, abi</p>
<ul>
<li>64bit synonyms: <code>x86_64</code>, <code>x64</code>, <code>amd64</code>, <code>intel 64</code></li>
<li>32bit synonyms: <code>x86</code>, <code>ia32</code>, <code>i386</code></li>
<li>ISA type: <code>CISC</code></li>
<li>Endianness: <code>little</code></li>
</ul>
<h2><a class="header" href="#registers" id="registers">Registers</a></h2>
<h3><a class="header" href="#general-purpose-register" id="general-purpose-register">General purpose register</a></h3>
<pre><code class="language-markdown">bytes
[7:0]      [3:0]   [1:0]   [1]   [0]     desc
----------------------------------------------------------
rax        eax     ax      ah    al      accumulator
rbx        ebx     bx      bh    bl      base register
rcx        ecx     cx      ch    cl      counter
rdx        edx     dx      dh    dl      data register
rsi        esi     si      -     sil     source index
rdi        edi     di      -     dil     destination index
rbp        ebp     bp      -     bpl     base pointer
rsp        esp     sp      -     spl     stack pointer
r8-15      rNd     rNw     -     rNb
</code></pre>
<h3><a class="header" href="#special-register" id="special-register">Special register</a></h3>
<pre><code class="language-markdown">bytes
[7:0]      [3:0]     [1:0]      desc
---------------------------------------------------
rflags     eflags    flags      flags register
rip        eip       ip         instruction pointer
</code></pre>
<h3><a class="header" href="#flags-register" id="flags-register">FLAGS register</a></h3>
<pre><code class="language-markdown">rflags
bits  desc
-----------------------------
[11]  OF overflow flag
[10]  DF direction flag
 [7]  SF sign flag
 [6]  ZF zero flag
 [4]  AF auxiliary carry flag
 [2]  PF parity flag
 [0]  CF carry flag
</code></pre>
<h2><a class="header" href="#addressing" id="addressing">Addressing</a></h2>
<pre><code class="language-asm">movw [rax], rbx         // save val in rbx at [rax]
movw [imm], rbx         // save val in rbx at [imm]
movw rax, [rbx+4*rcx]   // load val at [rbx+4*rcx] into rax
</code></pre>
<p><code>rip</code> relative addressing:</p>
<pre><code class="language-asm">lea rax, [rip+.my_str]       // load addr of .my_str into rax
...
.my_str:
.asciz &quot;Foo&quot;
</code></pre>
<h2><a class="header" href="#size-directives" id="size-directives">Size directives</a></h2>
<p>Explicitly specify size of the operation.</p>
<pre><code class="language-x86asm">mov  byte ptr [rax], 0xff    // save 1 byte(s) at [rax]
mov  word ptr [rax], 0xff    // save 2 byte(s) at [rax]
mov dword ptr [rax], 0xff    // save 4 byte(s) at [rax]
mov qword ptr [rax], 0xff    // save 8 byte(s) at [rax]
</code></pre>
<h2><a class="header" href="#a-hrefhttpswwwuclibcorgdocspsabi-x86_64pdfsysv-x86_64-abia" id="a-hrefhttpswwwuclibcorgdocspsabi-x86_64pdfsysv-x86_64-abia"><a href="https://www.uclibc.org/docs/psABI-x86_64.pdf">SysV x86_64 ABI</a></a></h2>
<h3><a class="header" href="#passing-arguments-to-functions" id="passing-arguments-to-functions">Passing arguments to functions</a></h3>
<ul>
<li>Integer/Pointer arguments
<pre><code class="language-markdown">reg     arg
-----------
rdi       1
rsi       2
rdx       3
rcx       4
r8        5
r9        6
</code></pre>
</li>
<li>Floating point arguments
<pre><code class="language-markdown">reg     arg
-----------
xmm0      1
  ..     ..
xmm7      8
</code></pre>
</li>
<li>Additional arguments are passed on the stack. Arguments are pushed
right-to-left (RTL), meaning next arguments are closer to current <code>rsp</code>.</li>
</ul>
<h3><a class="header" href="#return-values-from-functions" id="return-values-from-functions">Return values from functions</a></h3>
<ul>
<li>Integer/Pointer return values
<pre><code class="language-markdown">reg          size
-----------------
rax        64 bit
rax+rdx   128 bit
</code></pre>
</li>
<li>Floating point return values:
<pre><code class="language-markdown">reg            size
-------------------
xmm0         64 bit
xmm0+xmm1   128 bit
</code></pre>
</li>
</ul>
<h3><a class="header" href="#caller-saved-registers" id="caller-saved-registers">Caller saved registers</a></h3>
<p>Caller must save these registers if they should be preserved across function
calls.</p>
<ul>
<li><code>rax</code></li>
<li><code>rcx</code></li>
<li><code>rdx</code></li>
<li><code>rsi</code></li>
<li><code>rdi</code></li>
<li><code>rsp</code></li>
<li><code>r8</code> - <code>r11</code></li>
</ul>
<h3><a class="header" href="#callee-saved-registers" id="callee-saved-registers">Callee saved registers</a></h3>
<p>Caller can expect these registers to be preserved across function calls. Callee
must must save these registers in case they are used.</p>
<ul>
<li><code>rbx</code></li>
<li><code>rbp</code></li>
<li><code>r12</code> – <code>r15</code></li>
</ul>
<h3><a class="header" href="#stack" id="stack">Stack</a></h3>
<ul>
<li>grows downwards</li>
<li>frames aligned on 16 byte boundary
<pre><code class="language-text">Hi ADDR
 |                +------------+
 |                | prev frame |
 |                +------------+ &lt;--- 16 byte aligned (X &amp; ~0xf)
 |       [rbp+8]  | saved RIP  |
 |       [rbp]    | saved RBP  |
 |       [rbp-8]  | func stack |
 |                | ...        |
 v                +------------+
Lo ADDR
</code></pre>
</li>
</ul>
<h3><a class="header" href="#function-prologue--epilogue" id="function-prologue--epilogue">Function prologue &amp; epilogue</a></h3>
<ul>
<li>prologue
<pre><code class="language-x86asm">push rbp        // save caller base pointer
mov rbp, rsp    // save caller stack pointer
</code></pre>
</li>
<li>epilogue
<pre><code class="language-x86asm">mov rsp, rbp    // restore caller stack pointer
pop rbp         // restore caller base pointer
</code></pre>
<blockquote>
<p>Equivalent to <code>leave</code> instruction.</p>
</blockquote>
</li>
</ul>
<h2><a class="header" href="#asm-skeleton" id="asm-skeleton">ASM skeleton</a></h2>
<p>Small assembler skeleton, ready to use with following properties:</p>
<ul>
<li>use raw Linux syscalls (<code>man 2 syscall</code> for ABI)</li>
<li>no <code>C runtime (crt)</code></li>
<li>gnu assembler <a href="https://sourceware.org/binutils/docs/as"><code>gas</code></a></li>
<li>intel syntax</li>
</ul>
<pre><code class="language-x86asm"># file: greet.s

    .intel_syntax noprefix

    .section .text, &quot;ax&quot;, @progbits
    .global _start
_start:
    mov rdi, 1                      # fd
    lea rsi, [rip + greeting]       # buf
    mov rdx, [rip + greeting_len]   # count
    mov rax, 1                      # write(2) syscall nr
    syscall

    mov rdi, 0                      # exit code
    mov rax, 60                     # exit(2) syscall nr
    syscall

    .section .rdonly, &quot;a&quot;, @progbits
greeting:
    .asciz &quot;Hi ASM-World!\n&quot;
greeting_len:
    .int .-greeting
</code></pre>
<blockquote>
<p>Syscall numbers are defined in <code>/usr/include/asm/unistd.h</code>.</p>
</blockquote>
<p>To compile and run:</p>
<pre><code class="language-bash">&gt; gcc -o greet greet.s -nostartfiles -nostdlib &amp;&amp; ./greet
Hi ASM-World!
</code></pre>
<h2><a class="header" href="#references-1" id="references-1">References</a></h2>
<ul>
<li><a href="https://www.uclibc.org/docs/psABI-x86_64.pdf">SystemV AMD64 ABI</a></li>
<li><a href="https://www.amd.com/system/files/TechDocs/24592.pdf">AMD64 Vol1: Application Programming</a></li>
<li><a href="https://www.amd.com/system/files/TechDocs/24593.pdf">AMD64 Vol2: System Programming</a></li>
<li><a href="https://www.amd.com/system/files/TechDocs/24594.pdf">AMD64 Vol3: General-Purpose &amp; System Instructions</a></li>
<li><a href="https://cs.brown.edu/courses/cs033/docs/guides/x64_cheatsheet.pdf">X86_64 Cheat-Sheet</a></li>
<li><a href="https://software.intel.com/content/www/us/en/develop/download/intel-64-and-ia-32-architectures-software-developers-manual-volume-1-basic-architecture.html">Intel 64 Vol1: Basic Architecture</a></li>
<li><a href="https://software.intel.com/content/www/us/en/develop/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-2a-2b-2c-and-2d-instruction-set-reference-a-z.html">Intel 64 Vol2: Instruction Set Reference</a></li>
<li><a href="https://software.intel.com/content/www/us/en/develop/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-3a-3b-3c-and-3d-system-programming-guide.html">Intel 64 Vol3: System Programming Guide</a></li>
<li><a href="https://sourceware.org/binutils/docs/as">GNU Assembler</a></li>
<li><a href="https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops">GNU Assembler Directives</a></li>
<li><a href="https://sourceware.org/binutils/docs/as/i386_002dDependent.html">GNU Assembler <code>x86_64</code> dependent features</a></li>
</ul>
<h1><a class="header" href="#arm64" id="arm64">arm64</a></h1>
<p>keywords: arm64, aarch64, abi</p>
<ul>
<li>64bit synonyms: <code>arm64</code>, <code>aarch64</code></li>
<li>ISA type: <code>RISC</code></li>
<li>Endianness: <code>little</code>, <code>big</code></li>
</ul>
<h2><a class="header" href="#registers-1" id="registers-1">Registers</a></h2>
<h3><a class="header" href="#general-purpose-registers" id="general-purpose-registers">General purpose registers</a></h3>
<pre><code class="language-markdown">bytes
[7:0]     [3:0]     desc
---------------------------------------------
x0-x28    w0-w28    general purpose registers
x29       w29       frame pointer (FP)
x30       w30       link register (LR)
sp        wsp       stack pointer (SP)
pc                  program counter (PC)
xzr       wzr       zero register
</code></pre>
<blockquote>
<p>Write to <code>wN</code> register clears upper 32bit.</p>
</blockquote>
<h3><a class="header" href="#special-registers-per-el" id="special-registers-per-el">Special registers per EL</a></h3>
<pre><code class="language-markdown">bytes
[7:0]       desc
---------------------------------------------
sp_el0      stack pointer EL0

sp_el1      stack pointer EL1
elr_el1     exception link register EL1
spsr_el1    saved process status register EL1

sp_el2      stack pointer EL2
elr_el2     exception link register EL2
spsr_el2    saved process status register EL2

sp_el3      stack pointer EL3
elr_el3     exception link register EL3
spsr_el3    saved process status register EL3
</code></pre>
<h2><a class="header" href="#instructions-cheatsheet" id="instructions-cheatsheet">Instructions cheatsheet</a></h2>
<h3><a class="header" href="#accessing-system-registers" id="accessing-system-registers">Accessing system registers</a></h3>
<p>Reading from system registers:</p>
<pre><code class="language-armasm">mrs x0, vbar_el1      // move vbar_el1 into x0
</code></pre>
<p>Writing to system registers:</p>
<pre><code class="language-armasm">msr vbar_el1, x0      // move x0 into vbar_el1
</code></pre>
<h3><a class="header" href="#control-flow-1" id="control-flow-1">Control Flow</a></h3>
<pre><code class="language-armasm">b &lt;offset&gt;    // relative forward/back branch
br &lt;Xn&gt;       // absolute branch to address in register Xn

// branch &amp; link, store return address in X30 (LR)
bl &lt;offset&gt;   // relative forward/back branch
blr &lt;Xn&gt;      // absolute branch to address in register Xn

ret {Xn}      // return to address in X30, or Xn if supplied
</code></pre>
<h2><a class="header" href="#addressing-1" id="addressing-1">Addressing</a></h2>
<h3><a class="header" href="#offset" id="offset">Offset</a></h3>
<pre><code class="language-armasm">ldr x0, [x1]                // x0 = [x1]
ldr x0, [x1, 8]             // x0 = [x1 + 8]
ldr x0, [x1, x2, lsl #3]    // x0 = [x1 + (x2&lt;&lt;3)]
ldr x0, [x1, w2, stxw]      // x0 = [x1 + sign_ext(w2)]
ldr x0, [x1, w2, stxw #3]   // x0 = [x1 + (sign_ext(w2)&lt;&lt;3)]
</code></pre>
<blockquote>
<p>Shift amount can either be <code>0</code> or <code>log2(access_size_bytes)</code>. Eg for 8byte
access it can either be <code>{0, 3}</code>.</p>
</blockquote>
<h3><a class="header" href="#index" id="index">Index</a></h3>
<pre><code class="language-armasm">ldr x0, [x1, 8]!    // pre-inc : x1+=8; x0 = [x1]
ldr x0, [x1], 8     // post-inc: x0 = [x1]; x1+=8
</code></pre>
<h3><a class="header" href="#pair-access" id="pair-access">Pair access</a></h3>
<pre><code class="language-armasm">ldp x1, x2, [x0]    // x1 = [x0]; x2 = [x0 + 8]
stp x1, x2, [x0]    // [x0] = x1; [x0 + 8] = x2
</code></pre>
<h2><a class="header" href="#procedure-call-standard-arm64-a-hrefhttpsgithubcomarm-softwareabi-aablobmasteraapcs64aapcs64rstaapcs64a" id="procedure-call-standard-arm64-a-hrefhttpsgithubcomarm-softwareabi-aablobmasteraapcs64aapcs64rstaapcs64a">Procedure Call Standard ARM64 (<a href="https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst"><code>aapcs64</code></a>)</a></h2>
<h3><a class="header" href="#passing-arguments-to-functions-1" id="passing-arguments-to-functions-1">Passing arguments to functions</a></h3>
<ul>
<li>Integer/Pointer arguments
<pre><code class="language-markdown">reg     arg
-----------
x0        1
..       ..
x7        8
</code></pre>
</li>
<li>Additional arguments are passed on the stack. Arguments are pushed
<code>right-to-left (RTL)</code>, meaning next arguments are closer to current <code>sp</code>.
<pre><code class="language-markdown">void take(..., int a9, int a10);
                   |       |   | ... |       Hi
                   |       +--&gt;| a10 |       |
                   +----------&gt;| a9  | &lt;-SP  |
                               +-----+       v
                               | ... |       Lo
</code></pre>
</li>
</ul>
<h3><a class="header" href="#return-values-from-functions-1" id="return-values-from-functions-1">Return values from functions</a></h3>
<ul>
<li>Integer/Pointer return values
<pre><code class="language-markdown">reg          size
-----------------
x0         64 bit
</code></pre>
</li>
</ul>
<h3><a class="header" href="#callee-saved-registers-1" id="callee-saved-registers-1">Callee saved registers</a></h3>
<ul>
<li><code>x19</code> - <code>x28</code></li>
<li><code>SP</code></li>
</ul>
<h3><a class="header" href="#stack-1" id="stack-1">Stack</a></h3>
<ul>
<li>full descending
<ul>
<li>full: <code>sp</code> points to the last used location (valid item)</li>
<li>descending: stack grows downwards</li>
</ul>
</li>
<li><code>sp</code> must be 16byte aligned when used to access memory for r/w</li>
<li><code>sp</code> must be 16byte aligned on public interface interfaces</li>
</ul>
<h3><a class="header" href="#frame-chain" id="frame-chain">Frame chain</a></h3>
<ul>
<li>linked list of stack-frames</li>
<li>each frame links to the frame of its caller by a <code>frame record</code>
<ul>
<li>a frame record is described as a <code>(FP,LR)</code> pair</li>
</ul>
</li>
<li><code>x29 (FP)</code> must point to the frame record of the current stack-frame
<pre><code class="language-markdown">      +------+                   Hi
      |   0  |     frame0        |
   +-&gt;|   0  |                   |
   |  |  ... |                   |
   |  +------+                   |
   |  |  LR  |     frame1        |
   +--|  FP  |&lt;-+                |
      | ...  |  |                |
      +------+  |                |
      |  LR  |  |  current       |
x29 -&gt;|  FP  |--+  frame         v
      | ...  |                   Lo
</code></pre>
</li>
<li>end of the frame chain is indicated by following frame record <code>(0,-)</code></li>
<li>location of the frame record in the stack frame is not specified</li>
</ul>
<h3><a class="header" href="#function-prologue--epilogue-1" id="function-prologue--epilogue-1">Function prologue &amp; epilogue</a></h3>
<ul>
<li>prologue
<pre><code class="language-armasm">sub sp, sp, 16
stp x29, x30, [sp]      // [sp] = x29; [sp + 8] = x30
mov x29, sp             // FP points to frame record
</code></pre>
</li>
<li>epilogue
<pre><code class="language-armasm">ldp x29, x30, [sp]      // x29 = [sp]; x30 = [sp + 8]
add sp, sp, 16
ret
</code></pre>
</li>
</ul>
<h2><a class="header" href="#asm-skeleton-1" id="asm-skeleton-1">ASM skeleton</a></h2>
<p>Small assembler skeleton, ready to use with following properties:</p>
<ul>
<li>use raw Linux syscalls (<code>man 2 syscall</code> for ABI)</li>
<li>no <code>C runtime (crt)</code></li>
<li>gnu assembler <a href="https://sourceware.org/binutils/docs/as"><code>gas</code></a></li>
</ul>
<pre><code class="language-armasm">// file: greet.S

#include &lt;asm/unistd.h&gt;      // syscall NRs

    .arch armv8-a

    .section .text, &quot;ax&quot;, @progbits
    .balign 4                // align code on 4byte boundary
    .global _start
_start:
    mov x0, 2                // fd
    ldr x1, =greeting        // buf
    ldr x2, =greeting_len    // &amp;len
    ldr x2, [x2]             // len
    mov w8, __NR_write       // write(2) syscall
    svc 0

    mov x0, 0                // exit code
    mov w8, __NR_exit        // exit(2) syscall
    svc 0

    .balign 8                // align data on 8byte boundary
    .section .rodata, &quot;a&quot;, @progbits
greeting:
    .asciz &quot;Hi ASM-World!\n&quot;
greeting_len:
    .int .-greeting
</code></pre>
<blockquote>
<p>man gcc: <code>file.S</code> assembler code that must be preprocessed.</p>
</blockquote>
<p>To cross-compile and run:</p>
<pre><code class="language-bash">&gt; aarch64-linux-gnu-g++ -o greet greet.S -nostartfiles -nostdlib          \
    -Wl,--dynamic-linker=/usr/aarch64-linux-gnu/lib/ld-linux-aarch64.so.1 \
  &amp;&amp; qemu-aarch64 ./greet
Hi ASM-World!
</code></pre>
<blockquote>
<p>Cross-compiling on <code>Ubuntu 20.04 (x86_64)</code>, paths might differ on other
distributions. Explicitly specifying the dynamic linker should not be
required when compiling natively on arm64.</p>
</blockquote>
<h2><a class="header" href="#references-2" id="references-2">References</a></h2>
<ul>
<li><a href="https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst">Procedure Call Standard ARM64</a></li>
<li><a href="https://developer.arm.com/documentation/den0024/latest">ARMv8-A Programmer's Guide</a></li>
<li><a href="https://developer.arm.com/documentation/ddi0487/latest">ARMv8-A Architecture Reference Manual</a></li>
<li><a href="https://developer.arm.com/documentation/dai0527/latest">AppNote: ARMv8 Bare-metal boot code</a></li>
<li><a href="https://sourceware.org/binutils/docs/as">GNU Assembler</a></li>
<li><a href="https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops">GNU Assembler Directives</a></li>
<li><a href="https://sourceware.org/binutils/docs/as/AArch64_002dDependent.html">GNU Assembler <code>AArch64</code> dependent features</a></li>
</ul>
<h1><a class="header" href="#armv7a" id="armv7a">armv7a</a></h1>
<p>keywords: arm, armv7, abi</p>
<ul>
<li>ISA type: <code>RISC</code></li>
<li>Endianness: <code>little</code>, <code>big</code></li>
</ul>
<h2><a class="header" href="#registers-2" id="registers-2">Registers</a></h2>
<h3><a class="header" href="#general-purpose-registers-1" id="general-purpose-registers-1">General purpose registers</a></h3>
<pre><code class="language-markdown">bytes
[3:0]     alt     desc
---------------------------------------------
r0-r12            general purpose registers
r11       fp
r13       sp      stack pointer
r14       lr      link register
r15       pc      program counter
</code></pre>
<h3><a class="header" href="#special-registers" id="special-registers">Special registers</a></h3>
<pre><code class="language-markdown">bytes
[3:0]             desc
---------------------------------------------
cpsr              current program status register
</code></pre>
<h3><a class="header" href="#cpsr-register" id="cpsr-register">CPSR register</a></h3>
<pre><code class="language-markdown">cpsr
bits  desc
-----------------------------
 [31]  N negative flag
 [30]  Z zero flag
 [29]  C carry flag
 [28]  V overflow flag
 [27]  Q cummulative saturation (sticky)
  [9]  E load/store endianness
  [8]  A disable asynchronous aborts
  [7]  I disable IRQ
  [6]  F disable FIQ
  [5]  T indicate Thumb state
[4:0]  M process mode (USR, FIQ, IRQ, SVC, ABT, UND, SYS)
</code></pre>
<h2><a class="header" href="#instructions-cheatsheet-1" id="instructions-cheatsheet-1">Instructions cheatsheet</a></h2>
<h3><a class="header" href="#accessing-system-registers-1" id="accessing-system-registers-1">Accessing system registers</a></h3>
<p>Reading from system registers:</p>
<pre><code class="language-armasm">mrs r0, cpsr      // move cpsr into r0
</code></pre>
<p>Writing to system registers:</p>
<pre><code class="language-armasm">msr cpsr, r0      // move r0 into cpsr
</code></pre>
<h3><a class="header" href="#control-flow-2" id="control-flow-2">Control Flow</a></h3>
<pre><code class="language-armasm">b &lt;lable&gt;     // relative forward/back branch
bl &lt;lable&gt;    // relative forward/back branch &amp; link return addr in r14 (LR)

// branch &amp; exchange (can change between ARM &amp; Thumb instruction set)
//   bit Rm[0] == 0 -&gt; ARM
//   bit Rm[0] == 1 -&gt; Thumb
bx &lt;Rm&gt;       // absolute branch to address in register Rm
blx &lt;Rm&gt;      // absolute branch to address in register Rm &amp;
              // link return addr in r14 (LR)
</code></pre>
<h3><a class="header" href="#loadstore" id="loadstore">Load/Store</a></h3>
<p>Different addressing modes.</p>
<pre><code class="language-armasm">str r1, [r0]         // [r0]=r1
str r1, [r0, #4]     // [r0+4]=r1
str r1, [r0, #4]!    // r0+=4; [r0]=r1
str r1, [r0], 4      // [r0]=r1; r0+=4
</code></pre>
<p>Load/store multiple registers full-descending.</p>
<pre><code class="language-armasm">stmfd r0!, {r1-r2, r5}    // r0-=4; [r0]=r5
                          // r0-=4; [r0]=r2
                          // r0-=4; [r0]=r1
ldmfd r0!, {r1-r2, r5}    // r1=[r0]; r0+=4
                          // r2=[r0]; r0+=4
                          // r5=[r0]; r0+=4
</code></pre>
<blockquote>
<p><code>!</code> is optional but has the effect to update the base pointer register <code>r0</code> here.</p>
</blockquote>
<p>Push/Pop</p>
<pre><code class="language-armasm">push {r0-r2}    // effectively stmfd sp!, {r0-r2}
pop {r0-r2}     // effectively ldmfd sp!, {r0-r2}
</code></pre>
<h2><a class="header" href="#procedure-call-standard-arm-a-hrefhttpsgithubcomarm-softwareabi-aablobmasteraapcs32aapcs32rstaapcs32a" id="procedure-call-standard-arm-a-hrefhttpsgithubcomarm-softwareabi-aablobmasteraapcs32aapcs32rstaapcs32a">Procedure Call Standard ARM (<a href="https://github.com/ARM-software/abi-aa/blob/master/aapcs32/aapcs32.rst"><code>aapcs32</code></a>)</a></h2>
<h3><a class="header" href="#passing-arguments-to-functions-2" id="passing-arguments-to-functions-2">Passing arguments to functions</a></h3>
<ul>
<li>integer/pointer arguments
<pre><code class="language-markdown">reg     arg
-----------
r0        1
..       ..
r3        4
</code></pre>
</li>
<li>a double word (64bit) is passed in two consecutive registers (eg <code>r1+r2</code>)</li>
<li>additional arguments are passed on the stack. Arguments are pushed
<code>right-to-left (RTL)</code>, meaning next arguments are closer to current <code>sp</code>.
<pre><code class="language-markdown">void take(..., int a5, int a6);
                   |       |   | ... |       Hi
                   |       +--&gt;| a6  |       |
                   +----------&gt;| a5  | &lt;-SP  |
                               +-----+       v
                               | ... |       Lo
</code></pre>
</li>
</ul>
<h3><a class="header" href="#return-values-from-functions-2" id="return-values-from-functions-2">Return values from functions</a></h3>
<ul>
<li>integer/pointer return values
<pre><code class="language-markdown">reg          size
-----------------
r0         32 bit
r0+r1      64 bit
</code></pre>
</li>
</ul>
<h3><a class="header" href="#callee-saved-registers-2" id="callee-saved-registers-2">Callee saved registers</a></h3>
<ul>
<li><code>r4</code> - <code>r11</code></li>
<li><code>sp</code></li>
</ul>
<h3><a class="header" href="#stack-2" id="stack-2">Stack</a></h3>
<ul>
<li>full descending
<ul>
<li>full: <code>sp</code> points to the last used location (valid item)</li>
<li>descending: stack grows downwards</li>
</ul>
</li>
<li><code>sp</code> must be 4byte aligned (word boundary) at all time</li>
<li><code>sp</code> must be 8byte aligned on public interface interfaces</li>
</ul>
<h3><a class="header" href="#frame-chain-1" id="frame-chain-1">Frame chain</a></h3>
<ul>
<li>not strictly required by each platform</li>
<li>linked list of stack-frames</li>
<li>each frame links to the frame of its caller by a <code>frame record</code>
<ul>
<li>a frame record is described as a <code>(FP,LR)</code> pair (2x32bit)</li>
</ul>
</li>
<li><code>r11 (FP)</code> must point to the frame record of the current stack-frame
<pre><code class="language-markdown">      +------+                   Hi
      |   0  |     frame0        |
   +-&gt;|   0  |                   |
   |  |  ... |                   |
   |  +------+                   |
   |  |  LR  |     frame1        |
   +--|  FP  |&lt;-+                |
      | ...  |  |                |
      +------+  |                |
      |  LR  |  |  current       |
r11 -&gt;|  FP  |--+  frame         v
      | ...  |                   Lo
</code></pre>
</li>
<li>end of the frame chain is indicated by following frame record <code>(0,-)</code></li>
<li>location of the frame record in the stack frame is not specified</li>
<li><code>r11</code> is not updated before the new frame record is fully constructed</li>
</ul>
<h3><a class="header" href="#function-prologue--epilogue-2" id="function-prologue--epilogue-2">Function prologue &amp; epilogue</a></h3>
<ul>
<li>prologue
<pre><code class="language-armasm">push {fp, lr}
mov fp, sp              // FP points to frame record
</code></pre>
</li>
<li>epilogue
<pre><code class="language-armasm">pop {fp, pc}            // pop LR directly into PC
</code></pre>
</li>
</ul>
<h2><a class="header" href="#asm-skeleton-2" id="asm-skeleton-2">ASM skeleton</a></h2>
<p>Small assembler skeleton, ready to use with following properties:</p>
<ul>
<li>use raw Linux syscalls (<code>man 2 syscall</code> for ABI)</li>
<li>no <code>C runtime (crt)</code></li>
<li>gnu assembler <a href="https://sourceware.org/binutils/docs/as"><code>gas</code></a></li>
</ul>
<pre><code class="language-armasm">// file: greet.S

#include &lt;asm/unistd.h&gt;      // syscall NRs

    .arch armv7-a

    .section .text, &quot;ax&quot;
    .balign 4

    // Emit `arm` instructions, same as `.arm` directive.
    .code 32
    .global _start
_start:
    // Branch with link and exchange instruction set.
    blx _do_greet

    mov r0, #0               // exit code
    mov r7, #__NR_exit       // exit(2) syscall
    swi 0x0

    // Emit `thumb` instructions, same as `.thumb` directive.
    .code 16
    .thumb_func
_do_greet:
    mov r0, #2               // fd
    ldr r1, =greeting        // buf
    ldr r2, =greeting_len    // &amp;len
    ldr r2, [r2]             // len
    mov r7, #__NR_write      // write(2) syscall
    swi 0x0

    // Branch and exchange instruction set.
    bx lr

    .balign 8                // align data on 8byte boundary
    .section .rodata, &quot;a&quot;
greeting:
    .asciz &quot;Hi ASM-World!\n&quot;
greeting_len:
    .int .-greeting
</code></pre>
<blockquote>
<p>man gcc: <code>file.S</code> assembler code that must be preprocessed.</p>
</blockquote>
<p>To cross-compile and run:</p>
<pre><code class="language-bash">&gt; arm-linux-gnueabi-gcc -o greet greet.S -nostartfiles -nostdlib  \
    -Wl,--dynamic-linker=/usr/arm-linux-gnueabi/lib/ld-linux.so.3 \
  &amp;&amp; qemu-arm ./greet
Hi ASM-World!
</code></pre>
<blockquote>
<p>Cross-compiling on <code>Ubuntu 20.04 (x86_64)</code>, paths might differ on other
distributions. Explicitly specifying the dynamic linker should not be
required when compiling natively on arm.</p>
</blockquote>
<h2><a class="header" href="#references-3" id="references-3">References</a></h2>
<ul>
<li><a href="https://github.com/ARM-software/abi-aa/blob/master/aapcs32/aapcs32.rst">Procedure Call Standard ARM</a></li>
<li><a href="https://developer.arm.com/documentation/den0013/latest">ARMv7-A Programmer's Guide</a></li>
<li><a href="https://developer.arm.com/documentation/ddi0406/latest">ARMv7-A Architecture Reference Manual</a></li>
<li><a href="https://sourceware.org/binutils/docs/as">GNU Assembler</a></li>
<li><a href="https://sourceware.org/binutils/docs/as/Pseudo-Ops.html#Pseudo-Ops">GNU Assembler Directives</a></li>
<li><a href="https://sourceware.org/binutils/docs/as/ARM_002dDependent.html">GNU Assembler <code>ARM</code> dependent features</a></li>
</ul>

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