From bac8a5d2822835cf47175d1162030653fadd5c09 Mon Sep 17 00:00:00 2001
From: johannst <johannst@users.noreply.github.com>
Date: Thu, 15 Feb 2024 23:29:57 +0000
Subject: deploy: 4485708c972815bbb6df7f5a228683aa855d553d

---
 tools/bash.html | 47 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 30 insertions(+), 17 deletions(-)

(limited to 'tools/bash.html')

diff --git a/tools/bash.html b/tools/bash.html
index 580e941..91d44cb 100644
--- a/tools/bash.html
+++ b/tools/bash.html
@@ -192,7 +192,7 @@
 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 $foo&quot; else bar=&quot;&quot;
+bar=${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
@@ -274,6 +274,19 @@ contains some nice visualization to explain bash redirections.</p>
 once.</p>
 <pre><code class="language-bash">vim -d &lt;(grep foo bar) &lt;(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>
@@ -296,11 +309,11 @@ once.</p>
 <h3 id="example"><a class="header" href="#example">Example</a></h3>
 <pre><code class="language-bash">#!/bin/bash
 function parse_args() {
-    while getopts &quot;f:c&quot; PARAM; do
+    while getopts "f:c" 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;;
+            f) echo "GOT -f $OPTARG";;
+            c) echo "GOT -c";;
+            *) echo "ERR: print usage"; exit 1;;
         esac
     done
     # users responsibility to reset OPTIND
@@ -320,14 +333,14 @@ The match results can be accessed via the <code>$BASH_REMATCH</code> variable:</
 <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
+    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 =~ &quot;foo&quot; ]]</code> will match against <code>&quot;foo&quot;</code> not <code>foo</code>!</p>
+<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>
@@ -358,11 +371,11 @@ against words generated by <code>option</code>.</p>
 # -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 "f" against words "foo" "foobar" "bar" and generate matches
+compgen -W "foo foobar bar" "f"
 
-# compare &quot;hom&quot; against file/dir names and generate matches
-compgen -d -f &quot;hom&quot;
+# 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>
@@ -374,12 +387,12 @@ compgen -d -f &quot;hom&quot;
     local curr=$2
     local prev=$3
 
-    local opts=&quot;-c -s -f -h&quot;
+    local opts="-c -s -f -h"
     case $prev in
-        -c) COMPREPLY=( $(compgen -W &quot;green red blue&quot; -- $curr) );;
-        -s) COMPREPLY=( $(compgen -W &quot;low high&quot; -- $curr) );;
+        -c) COMPREPLY=( $(compgen -W "green red blue" -- $curr) );;
+        -s) COMPREPLY=( $(compgen -W "low high" -- $curr) );;
         -f) COMPREPLY=( $(compgen -f -- $curr) );;
-        *)  COMPREPLY=( $(compgen -W &quot;$opts&quot; -- $curr) );;
+        *)  COMPREPLY=( $(compgen -W "$opts" -- $curr) );;
     esac
 }
 
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