From be5e0048913797f2ef91065908730da025113c34 Mon Sep 17 00:00:00 2001
From: Egor Tensin <egor@tensin.name>
Date: Sat, 6 Jun 2026 22:23:54 +0200
Subject: move Jekyll source files to src/

---
 src/_notes/bash.html | 184 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 184 insertions(+)
 create mode 100644 src/_notes/bash.html

(limited to 'src/_notes/bash.html')

diff --git a/src/_notes/bash.html b/src/_notes/bash.html
new file mode 100644
index 0000000..c401522
--- /dev/null
+++ b/src/_notes/bash.html
@@ -0,0 +1,184 @@
+---
+title: bash
+subtitle: best practices
+layout: nosidebar
+links:
+  - {rel: stylesheet, href: 'assets/css/guides.css'}
+features:
+  - title: Script header
+    topics:
+      - do:
+          - |
+            #!/usr/bin/env bash
+
+            set -o errexit -o nounset -o pipefail
+            shopt -s inherit_errexit lastpipe
+        dont:
+          - |
+            #!/bin/sh -e
+  - title: Arrays
+    topics:
+      - title: Declaration
+        do:
+          - |
+            local -a xs=()
+            declare -a xs=()
+            local -A xs=()
+            declare -A xs=()
+        dont:
+          - |
+            local -a xs
+            declare -a xs
+            local -A xs
+            declare -A xs
+
+            # Doesn't work with nounset:
+            echo "${#xs[@]}"
+      - title: Expansion
+        do:
+          - |
+            func ${arr[@]+"${arr[@]}"}
+        dont:
+          - |
+            # Doesn't work with nounset:
+            func "${arr[@]}"
+          - |
+            # Expands to 0 arguments instead of 1:
+            declare -a arr=('')
+            func "${arr[@]+"${arr[@]}"}"
+      - title: unset
+        do:
+          - |
+            unset -v 'arr[x]'
+            unset -v 'arr[$i]'
+        dont:
+          - |
+            # May break due to globbing:
+            unset -v arr[x]
+            # In addition, possible quoting problem:
+            unset -v arr[$i]
+            # Doesn't work for some reason:
+            unset -v 'arr["x"]'
+            unset -v 'arr["]"]'
+            # Also rejected:
+            unset -v 'arr["$i"]'
+
+            # An insightful discussion on the topic:
+            # https://lists.gnu.org/archive/html/help-bash/2016-09/msg00020.html
+  - title: errexit
+    topics:
+      - title: Command substitution
+        do:
+          - |
+            shopt -s inherit_errexit
+
+            foo() { echo foo ; }
+            bar() { false ; echo bar >&2 ; }
+
+            output="$( bar )"
+            foo "$output"
+
+            # If inherit_errexit is unavailable, you can do
+            #output="$( set -e; bar )"
+        dont:
+          - |
+            foo() { echo foo ; }
+            bar() { false ; echo bar >&2 ; }
+
+            # This will print both "foo" and "bar":
+            foo "$( bar )"
+            # This will also print "foo":
+            foo "$( false )"
+          - |
+            foo() { echo foo ; }
+            bar() { false ; echo bar >&2 ; }
+
+            # This will still print both "foo" and "bar".
+            output="$( bar )"
+            foo "$output"
+
+            # This won't print anything.
+            output="$( false )"
+            foo "$output"
+      - title: Process substitution
+        do:
+          - |
+            shopt -s lastpipe
+
+            result=()
+            cmd | while IFS= read -r line; do
+                result+=("$( process_line "$line" )")
+            done
+        dont:
+          - |
+            # Without lastpipe, the loop is executed is a subshell,
+            # and the array will be empty:
+            result=()
+            cmd | while IFS= read -r line; do
+                result+=("$( process_line "$line" )")
+            done
+          - |
+            # errexit doesn't work for <( cmd ) no matter what:
+            while IFS= read -r line; do
+                process_line "$line"
+            done < <( cmd )
+            # This will be printed even if cmd fails:
+            echo 'should never see this'
+          - |
+            # This breaks if $output contains the \0 byte:
+            output="$( cmd )"
+
+            while IFS= read -r line; do
+                process_line "$line"
+            done <<< "$output"
+      - title: Functions
+        do:
+          - |
+            foo() { false ; echo foo >&2 ; }
+
+            foo
+            echo ok
+        dont:
+          - |
+            foo() { false ; echo foo >&2 ; }
+
+            # This will print "foo" no matter what.
+            if foo; then
+                echo ok
+            fi
+
+            # Same below.
+            foo && echo ok
+            foo || echo fail
+
+            # It currently appears to be completely impossible to
+            # execute a function inside a conditional with errexit
+            # enabled. Therefore, you should try to avoid this
+            # whenever possible.
+---
+{% for feature in page.features %}
+  <h2>{{ feature.title }}</h2>
+  {% for topic in feature.topics %}
+    {% if topic.title %}
+      <h3>{{ topic.title }}</h3>
+    {% endif %}
+    <div class="row">
+      <div class="col-md-6">
+        {% for guide in topic.do %}
+          <div class="pre_container pre_do">
+            {% highlight bash %}{{ guide }}{% endhighlight %}
+            <div class="pre_mark"><span class="glyphicon glyphicon-ok"></span></div>
+          </div>
+        {% endfor %}
+      </div>
+      <div class="col-md-6">
+        {% for guide in topic.dont %}
+          <div class="pre_container pre_dont">
+            {% highlight bash %}{{ guide }}{% endhighlight %}
+            <div class="pre_mark"><span class="glyphicon glyphicon-remove"></span></div>
+          </div>
+        {% endfor %}
+      </div>
+    </div>
+  {% endfor %}
+{% endfor %}
-- 
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