diff options
| author | johannst <johannst@users.noreply.github.com> | 2024-05-01 17:39:45 +0000 |
|---|---|---|
| committer | johannst <johannst@users.noreply.github.com> | 2024-05-01 17:39:45 +0000 |
| commit | 21a13652df728c9571f899caf4949d5d46f49db7 (patch) | |
| tree | dcd723453f6405c53a162da4c95896f5768f13d2 /shells/bash.html | |
| parent | 269caa8ae18eb33e1286e4c21d434ea07228a619 (diff) | |
| download | notes-21a13652df728c9571f899caf4949d5d46f49db7.tar.gz notes-21a13652df728c9571f899caf4949d5d46f49db7.zip | |
deploy: 7ca41565c4e70b212cb88a4d18c18fa35768df6d
Diffstat (limited to 'shells/bash.html')
| -rw-r--r-- | shells/bash.html | 457 |
1 files changed, 457 insertions, 0 deletions
diff --git a/shells/bash.html b/shells/bash.html new file mode 100644 index 0000000..fe98ee4 --- /dev/null +++ b/shells/bash.html @@ -0,0 +1,457 @@ +<!DOCTYPE HTML> +<html lang="en" class="light" dir="ltr"> + <head> + <!-- Book generated using mdBook --> + <meta charset="UTF-8"> + <title>bash - Notes</title> + + + <!-- Custom HTML head --> + + <meta name="description" content=""> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <meta name="theme-color" content="#ffffff"> + + <link rel="icon" href="../favicon.svg"> + <link rel="shortcut icon" href="../favicon.png"> + <link rel="stylesheet" href="../css/variables.css"> + <link rel="stylesheet" href="../css/general.css"> + <link rel="stylesheet" href="../css/chrome.css"> + <link rel="stylesheet" href="../css/print.css" media="print"> + + <!-- Fonts --> + <link rel="stylesheet" href="../FontAwesome/css/font-awesome.css"> + <link rel="stylesheet" href="../fonts/fonts.css"> + + <!-- Highlight.js Stylesheets --> + <link rel="stylesheet" href="../highlight.css"> + <link rel="stylesheet" href="../tomorrow-night.css"> + <link rel="stylesheet" href="../ayu-highlight.css"> + + <!-- Custom theme stylesheets --> + + </head> + <body class="sidebar-visible no-js"> + <div id="body-container"> + <!-- Provide site root to javascript --> + <script> + var path_to_root = "../"; + var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light"; + </script> + + <!-- Work around some values being stored in localStorage wrapped in quotes --> + <script> + try { + var theme = localStorage.getItem('mdbook-theme'); + var sidebar = localStorage.getItem('mdbook-sidebar'); + + if (theme.startsWith('"') && theme.endsWith('"')) { + localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1)); + } + + if (sidebar.startsWith('"') && sidebar.endsWith('"')) { + localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1)); + } + } catch (e) { } + </script> + + <!-- Set the theme before any content is loaded, prevents flash --> + <script> + var theme; + try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { } + if (theme === null || theme === undefined) { theme = default_theme; } + var html = document.querySelector('html'); + html.classList.remove('light') + html.classList.add(theme); + var body = document.querySelector('body'); + body.classList.remove('no-js') + body.classList.add('js'); + </script> + + <input type="checkbox" id="sidebar-toggle-anchor" class="hidden"> + + <!-- Hide / unhide sidebar before it is displayed --> + <script> + var body = document.querySelector('body'); + var sidebar = null; + var sidebar_toggle = document.getElementById("sidebar-toggle-anchor"); + if (document.body.clientWidth >= 1080) { + try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { } + sidebar = sidebar || 'visible'; + } else { + sidebar = 'hidden'; + } + sidebar_toggle.checked = sidebar === 'visible'; + body.classList.remove('sidebar-visible'); + body.classList.add("sidebar-" + sidebar); + </script> + + <nav id="sidebar" class="sidebar" aria-label="Table of contents"> + <div class="sidebar-scrollbox"> + <ol class="chapter"><li class="chapter-item expanded affix "><a href="../intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="../shells/index.html"><strong aria-hidden="true">1.</strong> Shells</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../shells/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="../shells/bash.html" class="active"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="../shells/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li></ol></li><li class="chapter-item expanded "><a href="../cli/index.html"><strong aria-hidden="true">2.</strong> CLI foo</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../cli/awk.html"><strong aria-hidden="true">2.1.</strong> awk</a></li><li class="chapter-item expanded "><a href="../cli/sed.html"><strong aria-hidden="true">2.2.</strong> sed</a></li><li class="chapter-item expanded "><a href="../cli/column.html"><strong aria-hidden="true">2.3.</strong> column</a></li><li class="chapter-item expanded "><a href="../cli/sort.html"><strong aria-hidden="true">2.4.</strong> sort</a></li><li class="chapter-item expanded "><a href="../cli/tr.html"><strong aria-hidden="true">2.5.</strong> tr</a></li></ol></li><li class="chapter-item expanded "><a href="../tools/index.html"><strong aria-hidden="true">3.</strong> Tools</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../tools/tmux.html"><strong aria-hidden="true">3.1.</strong> tmux</a></li><li class="chapter-item expanded "><a href="../tools/emacs.html"><strong aria-hidden="true">3.2.</strong> emacs</a></li><li class="chapter-item expanded "><a href="../tools/gpg.html"><strong aria-hidden="true">3.3.</strong> gpg</a></li><li class="chapter-item expanded "><a href="../tools/radare2.html"><strong aria-hidden="true">3.4.</strong> radare2</a></li><li class="chapter-item expanded "><a href="../tools/qemu.html"><strong aria-hidden="true">3.5.</strong> qemu</a></li><li class="chapter-item expanded "><a href="../tools/pacman.html"><strong aria-hidden="true">3.6.</strong> pacman</a></li><li class="chapter-item expanded "><a href="../tools/dot.html"><strong aria-hidden="true">3.7.</strong> dot</a></li><li class="chapter-item expanded "><a href="../tools/ffmpeg.html"><strong aria-hidden="true">3.8.</strong> ffmpeg</a></li><li class="chapter-item expanded "><a href="../tools/gnuplot.html"><strong aria-hidden="true">3.9.</strong> gnuplot</a></li><li class="chapter-item expanded "><a href="../tools/restic.html"><strong aria-hidden="true">3.10.</strong> restic</a></li></ol></li><li class="chapter-item expanded "><a href="../monitor/index.html"><strong aria-hidden="true">4.</strong> Resource analysis & monitor</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../monitor/lsof.html"><strong aria-hidden="true">4.1.</strong> lsof</a></li><li class="chapter-item expanded "><a href="../monitor/pidstat.html"><strong aria-hidden="true">4.2.</strong> pidstat</a></li><li class="chapter-item expanded "><a href="../monitor/pgrep.html"><strong aria-hidden="true">4.3.</strong> pgrep</a></li><li class="chapter-item expanded "><a href="../monitor/ps.html"><strong aria-hidden="true">4.4.</strong> ps</a></li><li class="chapter-item expanded "><a href="../monitor/pmap.html"><strong aria-hidden="true">4.5.</strong> pmap</a></li><li class="chapter-item expanded "><a href="../monitor/pstack.html"><strong aria-hidden="true">4.6.</strong> pstack</a></li></ol></li><li class="chapter-item expanded "><a href="../trace_profile/index.html"><strong aria-hidden="true">5.</strong> Trace and Profile</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../trace_profile/time.html"><strong aria-hidden="true">5.1.</strong> time</a></li><li class="chapter-item expanded "><a href="../trace_profile/strace.html"><strong aria-hidden="true">5.2.</strong> strace</a></li><li class="chapter-item expanded "><a href="../trace_profile/ltrace.html"><strong aria-hidden="true">5.3.</strong> ltrace</a></li><li class="chapter-item expanded "><a href="../trace_profile/perf.html"><strong aria-hidden="true">5.4.</strong> perf</a></li><li class="chapter-item expanded "><a href="../trace_profile/oprofile.html"><strong aria-hidden="true">5.5.</strong> OProfile</a></li><li class="chapter-item expanded "><a href="../trace_profile/callgrind.html"><strong aria-hidden="true">5.6.</strong> callgrind</a></li></ol></li><li class="chapter-item expanded "><a href="../debug/index.html"><strong aria-hidden="true">6.</strong> Debug</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../debug/gdb.html"><strong aria-hidden="true">6.1.</strong> gdb</a></li><li class="chapter-item expanded "><a href="../debug/gdbserver.html"><strong aria-hidden="true">6.2.</strong> gdbserver</a></li></ol></li><li class="chapter-item expanded "><a href="../binary/index.html"><strong aria-hidden="true">7.</strong> Binary</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../binary/od.html"><strong aria-hidden="true">7.1.</strong> od</a></li><li class="chapter-item expanded "><a href="../binary/xxd.html"><strong aria-hidden="true">7.2.</strong> xxd</a></li><li class="chapter-item expanded "><a href="../binary/readelf.html"><strong aria-hidden="true">7.3.</strong> readelf</a></li><li class="chapter-item expanded "><a href="../binary/objdump.html"><strong aria-hidden="true">7.4.</strong> objdump</a></li><li class="chapter-item expanded "><a href="../binary/nm.html"><strong aria-hidden="true">7.5.</strong> nm</a></li></ol></li><li class="chapter-item expanded "><a href="../development/index.html"><strong aria-hidden="true">8.</strong> Development</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../development/c++filt.html"><strong aria-hidden="true">8.1.</strong> c++filt</a></li><li class="chapter-item expanded "><a href="../development/c++.html"><strong aria-hidden="true">8.2.</strong> c++</a></li><li class="chapter-item expanded "><a href="../development/glibc.html"><strong aria-hidden="true">8.3.</strong> glibc</a></li><li class="chapter-item expanded "><a href="../development/gcc.html"><strong aria-hidden="true">8.4.</strong> gcc</a></li><li class="chapter-item expanded "><a href="../development/git.html"><strong aria-hidden="true">8.5.</strong> git</a></li><li class="chapter-item expanded "><a href="../development/cmake.html"><strong aria-hidden="true">8.6.</strong> cmake</a></li><li class="chapter-item expanded "><a href="../development/make.html"><strong aria-hidden="true">8.7.</strong> make</a></li><li class="chapter-item expanded "><a href="../development/ld.so.html"><strong aria-hidden="true">8.8.</strong> ld.so</a></li><li class="chapter-item expanded "><a href="../development/symbolver.html"><strong aria-hidden="true">8.9.</strong> symbol versioning</a></li><li class="chapter-item expanded "><a href="../development/python.html"><strong aria-hidden="true">8.10.</strong> python</a></li><li class="chapter-item expanded "><a href="../development/gcov.html"><strong aria-hidden="true">8.11.</strong> gcov</a></li><li class="chapter-item expanded "><a href="../development/pgo.html"><strong aria-hidden="true">8.12.</strong> pgo</a></li></ol></li><li class="chapter-item expanded "><a href="../linux/index.html"><strong aria-hidden="true">9.</strong> Linux</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../linux/systemd.html"><strong aria-hidden="true">9.1.</strong> systemd</a></li><li class="chapter-item expanded "><a href="../linux/coredump.html"><strong aria-hidden="true">9.2.</strong> coredump</a></li><li class="chapter-item expanded "><a href="../linux/ptrace_scope.html"><strong aria-hidden="true">9.3.</strong> ptrace_scope</a></li><li class="chapter-item expanded "><a href="../linux/cryptsetup.html"><strong aria-hidden="true">9.4.</strong> cryptsetup</a></li><li class="chapter-item expanded "><a href="../linux/swap.html"><strong aria-hidden="true">9.5.</strong> swap</a></li><li class="chapter-item expanded "><a href="../linux/input.html"><strong aria-hidden="true">9.6.</strong> input</a></li><li class="chapter-item expanded "><a href="../linux/acl.html"><strong aria-hidden="true">9.7.</strong> acl</a></li><li class="chapter-item expanded "><a href="../linux/zfs.html"><strong aria-hidden="true">9.8.</strong> zfs</a></li></ol></li><li class="chapter-item expanded "><a href="../network/index.html"><strong aria-hidden="true">10.</strong> Network</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../network/ss.html"><strong aria-hidden="true">10.1.</strong> ss</a></li><li class="chapter-item expanded "><a href="../network/tcpdump.html"><strong aria-hidden="true">10.2.</strong> tcpdump</a></li><li class="chapter-item expanded "><a href="../network/tshark.html"><strong aria-hidden="true">10.3.</strong> tshark</a></li><li class="chapter-item expanded "><a href="../network/firewall-cmd.html"><strong aria-hidden="true">10.4.</strong> firewall-cmd</a></li><li class="chapter-item expanded "><a href="../network/nftables.html"><strong aria-hidden="true">10.5.</strong> nftables</a></li></ol></li><li class="chapter-item expanded "><a href="../web/index.html"><strong aria-hidden="true">11.</strong> Web</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../web/html.html"><strong aria-hidden="true">11.1.</strong> html</a></li><li class="chapter-item expanded "><a href="../web/css.html"><strong aria-hidden="true">11.2.</strong> css</a></li><li class="chapter-item expanded "><a href="../web/chartjs.html"><strong aria-hidden="true">11.3.</strong> chartjs</a></li></ol></li><li class="chapter-item expanded "><a href="../arch/index.html"><strong aria-hidden="true">12.</strong> Arch</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../arch/x86_64.html"><strong aria-hidden="true">12.1.</strong> x86_64</a></li><li class="chapter-item expanded "><a href="../arch/armv8.html"><strong aria-hidden="true">12.2.</strong> armv8</a></li><li class="chapter-item expanded "><a href="../arch/arm64.html"><strong aria-hidden="true">12.3.</strong> arm64</a></li><li class="chapter-item expanded "><a href="../arch/armv7.html"><strong aria-hidden="true">12.4.</strong> armv7</a></li><li class="chapter-item expanded "><a href="../arch/riscv.html"><strong aria-hidden="true">12.5.</strong> riscv</a></li></ol></li></ol> + </div> + <div id="sidebar-resize-handle" class="sidebar-resize-handle"> + <div class="sidebar-resize-indicator"></div> + </div> + </nav> + + <!-- Track and set sidebar scroll position --> + <script> + var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox'); + sidebarScrollbox.addEventListener('click', function(e) { + if (e.target.tagName === 'A') { + sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop); + } + }, { passive: true }); + var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll'); + sessionStorage.removeItem('sidebar-scroll'); + if (sidebarScrollTop) { + // preserve sidebar scroll position when navigating via links within sidebar + sidebarScrollbox.scrollTop = sidebarScrollTop; + } else { + // scroll sidebar to current active section when navigating via "next/previous chapter" buttons + var activeSection = document.querySelector('#sidebar .active'); + if (activeSection) { + activeSection.scrollIntoView({ block: 'center' }); + } + } + </script> + + <div id="page-wrapper" class="page-wrapper"> + + <div class="page"> + <div id="menu-bar-hover-placeholder"></div> + <div id="menu-bar" class="menu-bar sticky"> + <div class="left-buttons"> + <label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar"> + <i class="fa fa-bars"></i> + </label> + <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list"> + <i class="fa fa-paint-brush"></i> + </button> + <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu"> + <li role="none"><button role="menuitem" class="theme" id="light">Light</button></li> + <li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li> + <li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li> + <li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li> + <li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li> + </ul> + <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> + <i class="fa fa-search"></i> + </button> + </div> + + <h1 class="menu-title">Notes</h1> + + <div class="right-buttons"> + <a href="../print.html" title="Print this book" aria-label="Print this book"> + <i id="print-button" class="fa fa-print"></i> + </a> + <a href="https://github.com/johannst/notes" title="Git repository" aria-label="Git repository"> + <i id="git-repository-button" class="fa fa-github"></i> + </a> + + </div> + </div> + + <div id="search-wrapper" class="hidden"> + <form id="searchbar-outer" class="searchbar-outer"> + <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> + </form> + <div id="searchresults-outer" class="searchresults-outer hidden"> + <div id="searchresults-header" class="searchresults-header"></div> + <ul id="searchresults"> + </ul> + </div> + </div> + + <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM --> + <script> + document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); + document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); + Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { + link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); + }); + </script> + + <div id="content" class="content"> + <main> + <h1 id="bash1"><a class="header" href="#bash1">bash(1)</a></h1> +<h2 id="expansion"><a class="header" href="#expansion">Expansion</a></h2> +<h3 id="generator"><a class="header" href="#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 id="parameter"><a class="header" href="#parameter">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="bla $foo" else bar="" + +# check param set +bar=${foo:?msg} # if $foo set, then bar=$foo else exit and print msg + +# indirect +FOO=foo +BAR=FOO +bar=${!BAR} # deref value of BAR -> bar=$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 + +# set programmatically with priintf builtin +printf -v "VAR1" "abc" +NAME=VAR2 +printf -v "$NAME" "%s" "def" +</code></pre> +<blockquote> +<p>Note: <code>prefix</code>/<code>suffix</code>/<code>pattern</code> are expanded as <a href="#pathname">pathnames</a>.</p> +</blockquote> +<h3 id="pathname"><a class="header" href="#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>With <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 id="io-redirection"><a class="header" href="#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 & stderr to file +command >file 2>&1 +# equivalent +command &>file + +# stderr to stdout & stdout to file +command 2>&1 >file +</code></pre> +<blockquote> +<p>The article <a href="https://catonmat.net/bash-one-liners-explained-part-three">Bash One-Liners Explained, Part III: All about +redirections</a> +contains some nice visualization to explain bash redirections.</p> +</blockquote> +<h3 id="explanation"><a class="header" href="#explanation">Explanation</a></h3> +<pre><code class="language-bash">j>&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>&1 >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 id="process-substitution-ref"><a class="header" href="#process-substitution-ref">Process substitution (<a href="https://tldp.org/LDP/abs/html/process-sub.html">ref</a>)</a></h2> +<p>Process substitution allows to redirect the stdout of multiple processes at +once.</p> +<pre><code class="language-bash">vim -d <(grep foo bar) <(grep foo moose) +</code></pre> +<h2 id="command-grouping"><a class="header" href="#command-grouping">Command grouping</a></h2> +<p>Execute commands in a group with or without subshell. Can be used to easily +redirect stdout/stderr of all commands in the group into one file.</p> +<pre><code class="language-bash"># Group commands without subshell. +v=abc ; { v=foo; echo $v; } ; echo $v +# foo +# foo + +# Group commands with subshell. +v=abc ; ( v=foo; echo $v; ) ; echo $v +# foo +# abc +</code></pre> +<h2 id="argument-parsing-with-getopts"><a class="header" href="#argument-parsing-with-getopts">Argument parsing with <code>getopts</code></a></h2> +<p>The <code>getopts</code> builtin uses following global variables:</p> +<ul> +<li><code>OPTARG</code>, value of last option argument</li> +<li><code>OPTIND</code>, index of the next argument to process (user must reset)</li> +<li><code>OPTERR</code>, display errors if set to <code>1</code></li> +</ul> +<pre><code class="language-bash">getopts <optstring> <param> [<args>] +</code></pre> +<ul> +<li><code><optstring></code> specifies the names of supported options, eg <code>f:c</code> +<ul> +<li><code>f:</code> means <code>-f</code> option with an argument</li> +<li><code>c</code> means <code>-c</code> option without an argument</li> +</ul> +</li> +<li><code><param></code> specifies a variable name which <code>getopts</code> fills with the last parsed option argument</li> +<li><code><args></code> optionally specify argument string to parse, by default <code>getopts</code> parses <code>$@</code></li> +</ul> +<h3 id="example"><a class="header" href="#example">Example</a></h3> +<pre><code class="language-bash">#!/bin/bash +function parse_args() { + while getopts "f:c" PARAM; do + case $PARAM in + f) echo "GOT -f $OPTARG";; + c) echo "GOT -c";; + *) echo "ERR: print usage"; exit 1;; + esac + done + # users responsibility to reset OPTIND + OPTIND=1 +} + +parse_args -f xxx -c +parse_args -f yyy +</code></pre> +<h2 id="regular-expressions"><a class="header" href="#regular-expressions">Regular Expressions</a></h2> +<p>Bash supports regular expression matching with the binary operator <code>=~</code>. +The match results can be accessed via the <code>$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 =~ $REGEX ]]; then + echo "${BASH_REMATCH[0]}" # title foo : 1234 + echo "${BASH_REMATCH[1]}" # foo + echo "${BASH_REMATCH[2]}" # 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 =~ "foo" ]]</code> will match against <code>"foo"</code> not <code>foo</code>!</p> +</blockquote> +<h2 id="completion"><a class="header" href="#completion">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 <func> <cmd> # install <func> as completion handler for <cmd> +complete -r <cmd> # uninstall completion handler for <cmd> +</code></pre> +<p>Variables available in completion functions:</p> +<pre><code class="language-bash"># in +$1 # <cmd> +$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 <option> <word> + +# usefule options: +# -W <list> 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 "f" against words "foo" "foobar" "bar" and generate matches +compgen -W "foo foobar bar" "f" + +# compare "hom" against file/dir names and generate matches +compgen -d -f "hom" +</code></pre> +<h3 id="example-1"><a class="header" href="#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-bash">foo -c green|red|blue -s low|high -f <file> -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="-c -s -f -h" + case $prev in + -c) COMPREPLY=( $(compgen -W "green red blue" -- $curr) );; + -s) COMPREPLY=( $(compgen -W "low high" -- $curr) );; + -f) COMPREPLY=( $(compgen -f -- $curr) );; + *) COMPREPLY=( $(compgen -W "$opts" -- $curr) );; + esac +} + +complete -F _foo foo +</code></pre> + + </main> + + <nav class="nav-wrapper" aria-label="Page navigation"> + <!-- Mobile navigation buttons --> + <a rel="prev" href="../shells/zsh.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + <a rel="next prefetch" href="../shells/fish.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + + <div style="clear: both"></div> + </nav> + </div> + </div> + + <nav class="nav-wide-wrapper" aria-label="Page navigation"> + <a rel="prev" href="../shells/zsh.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + <a rel="next prefetch" href="../shells/fish.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + </nav> + + </div> + + + + + <script> + window.playground_copyable = true; + </script> + + + <script src="../elasticlunr.min.js"></script> + <script src="../mark.min.js"></script> + <script src="../searcher.js"></script> + + <script src="../clipboard.min.js"></script> + <script src="../highlight.js"></script> + <script src="../book.js"></script> + + <!-- Custom JS scripts --> + + + </div> + </body> +</html> |