Fix redirects
This commit is contained in:
Rico Sta. Cruz
parent
ee90312092
commit
edfdfb794a
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@ -3,6 +3,10 @@ whitelist:
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- jekyll-redirect-from
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- jekyll-github-metadata
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plugins:
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- jekyll-redirect-from
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- jekyll-github-metadata
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# files
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exclude:
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- Makefile
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@ -0,0 +1,10 @@
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<!DOCTYPE html>
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<html lang="en-US">
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<meta charset="utf-8">
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<title>Redirecting…</title>
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<link rel="canonical" href="{{ page.redirect.to | remove: '.html' }}">
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<meta http-equiv="refresh" content="0; url={{ page.redirect.to | remove: '.html' }}">
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<h1>Redirecting...</h1>
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<a href="{{ page.redirect.to | remove: '.html' }}">Click here if you are not redirected.</a>
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<script>location="{{ page.redirect.to | remove: '.html' }}"</script>
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</html>
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575
bash.md
575
bash.md
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@ -1,5 +1,578 @@
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---
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title: Bash scripting
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category: CLI
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redirect_to: /sh
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layout: 2017/sheet
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tags: [Featured]
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redirect_from:
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- /sh
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- /sh.html
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---
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Getting started
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---------------
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{: .-three-column}
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### Example
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```bash
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#!/usr/bin/env bash
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NAME="John"
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echo "Hello $NAME!"
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```
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### Variables
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```bash
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NAME="John"
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echo $NAME
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echo "$NAME"
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echo "${NAME}!"
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```
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### String quotes
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```bash
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NAME="John"
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echo "Hi $NAME" #=> Hi John
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echo 'Hi $NAME' #=> Hi $NAME
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```
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### Shell execution
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```bash
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echo "I'm in $(pwd)"
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echo "I'm in `pwd`"
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# Same
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```
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See [Command substitution](http://wiki.bash-hackers.org/syntax/expansion/cmdsubst)
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### Conditional execution
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```bash
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git commit && git push
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git commit || echo "Commit failed"
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```
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### Functions
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{: id='functions-example'}
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```bash
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get_name() {
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echo "John"
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}
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echo "You are $(get_name)"
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```
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See: [Functions](#functions)
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### Conditionals
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{: id='conditionals-example'}
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```bash
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if [ -z "$string" ]; then
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echo "String is empty"
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elsif [ -n "$string" ]; then
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echo "String is not empty"
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fi
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```
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See: [Conditionals](#conditionals)
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### Strict mode
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```bash
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set -euo pipefail
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IFS=$'\n\t'
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```
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See: [Unofficial bash strict mode](http://redsymbol.net/articles/unofficial-bash-strict-mode/)
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### Brace expansion
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```bash
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echo {A,B}.js
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```
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| `{A,B}` | Same as `A B` |
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| `{A,B}.js` | Same as `A.js B.js` |
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| `{1..5}` | Same as `1 2 3 4 5` |
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See: [Brace expansion](http://wiki.bash-hackers.org/syntax/expansion/brace)
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Parameter expansions
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--------------------
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{: .-three-column}
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### Basics
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```bash
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name="John"
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echo ${name}
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echo ${name/J/j} #=> "john" (substitution)
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echo ${name:0:2} #=> "jo" (slicing)
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echo ${food:-Cake} #=> $food or "Cake"
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```
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```bash
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length=2
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echo ${name:0:length} #=> "jo"
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```
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See: [Parameter expansion](http://wiki.bash-hackers.org/syntax/pe)
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```bash
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STR="/path/to/foo.cpp"
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echo ${STR%.cpp} # /path/to/foo
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echo ${STR%.cpp}.o # /path/to/foo.o
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echo ${STR##*.} # cpp (extension)
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echo ${STR##*/} # foo.cpp (basepath)
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echo ${STR#*/} # path/to/foo.cpp
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echo ${STR##*/} # foo.cpp
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echo ${STR/foo/bar} # /path/to/bar.cpp
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```
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```bash
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STR="Hello world"
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echo ${STR:6:5} # "world"
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echo ${STR:-5:5} # "world"
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```
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```bash
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SRC="/path/to/foo.cpp"
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BASE=${STR##*/} #=> "foo.cpp" (basepath)
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DIR=${SRC%$BASE} #=> "/path/to" (dirpath)
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```
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### Substitution
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| Code | Description |
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| --- | --- |
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| `${FOO%suffix}` | Remove suffix |
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| `${FOO#prefix}` | Remove prefix |
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| --- | --- |
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| `${FOO%%suffix}` | Remove long suffix |
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| `${FOO##prefix}` | Remove long prefix |
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| --- | --- |
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| `${FOO/from/to}` | Replace first match |
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| `${FOO//from/to}` | Replace all |
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| --- | --- |
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| `${FOO/%from/to}` | Replace suffix |
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| `${FOO/#from/to}` | Replace prefix |
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### Substrings
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| `${FOO:0:3}` | Substring _(position, length)_ |
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| `${FOO:-3:3}` | Substring from the right |
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### Length
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| `${#FOO}` | Length of `$FOO` |
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### Default values
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| `${FOO:-val}` | `$FOO`, or `val` if not set |
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| `${FOO:=val}` | Set `$FOO` to `val` if not set |
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| `${FOO:+val}` | `val` if `$FOO` is set |
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| `${FOO:?message}` | Show error message ande xit if `$FOO` is not set |
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The `:` is optional (eg, `${FOO=word}` works)
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Loops
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-----
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{: .-three-column}
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### Basic for loop
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```bash
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for i in /etc/rc.*; do
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echo $i
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done
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```
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### Ranges
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```bash
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for i in {1..5}; do
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echo "Welcome $i"
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done
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```
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### Reading lines
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```bash
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cat file.txt | while read line; do
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echo $line
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done
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```
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### Forever
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```bash
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while true; do
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···
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done
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```
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Functions
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---------
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{: .-three-column}
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### Defining functions
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```bash
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myfunc() {
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echo "hello $1"
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}
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```
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```bash
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# Same as above (alternate syntax)
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function myfunc() {
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echo "hello $1"
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}
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```
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```bash
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myfunc "John"
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```
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### Returning values
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```bash
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myfunc() {
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local myresult='some value'
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echo $myresult
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}
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```
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```bash
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result=$(myfunc)
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```
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### Raising errors
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```bash
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myfunc() {
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return 1
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}
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```
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```bash
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if myfunc; then
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echo "success"
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else
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echo "failure"
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fi
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```
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### Arguments
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| Expression | Description |
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| --- | --- |
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| `$#` | Number of arguments |
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| `$*` | All arguments |
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| `$@` | All arguments, starting from first |
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| `$1` | First argument |
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See [Special parameters](http://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables).
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Conditionals
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------------
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{: .-three-column}
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### Conditions
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| Condition | Description |
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| --- | --- |
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| `[ -z STRING ]` | Empty string |
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| `[ -n STRING ]` | Not empty string |
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| --- | --- |
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| `[ NUM -eq NUM ]` | Equal |
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| `[ NUM -ne NUM ]` | Not equal |
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| `[ NUM -lt NUM ]` | Less than |
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| `[ NUM -le NUM ]` | Less than or equal |
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| `[ NUM -gt NUM ]` | Greater than |
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| `[ NUM -ge NUM ]` | Greater than or equal |
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| --- | --- |
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| `[[ STRING =~ STRING ]]` | Regexp |
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| --- | --- |
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| `(( NUM < NUM ))` | Numeric conditions |
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| Condition | Description |
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| --- | --- |
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| `[ -o noclobber ]` | If OPTIONNAME is enabled |
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| --- | --- |
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| `[ ! EXPR ]` | Not |
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| `[ X ] && [ Y ]` | And |
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| `[ X ] || [ Y ]` | Or |
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### File conditions
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| Condition | Description |
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| --- | --- |
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| `[ -e FILE ]` | Exists |
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| `[ -r FILE ]` | Readable |
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| `[ -h FILE ]` | Symlink |
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| `[ -d FILE ]` | Directory |
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| `[ -w FILE ]` | Writable |
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| `[ -s FILE ]` | Size is > 0 bytes |
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| `[ -f FILE ]` | File |
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| `[ -x FILE ]` | Executable |
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| --- | --- |
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| `[ FILE1 -nt FILE2 ]` | 1 is more recent than 2 |
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| `[ FILE1 -ot FILE2 ]` | 2 is more recent than 1 |
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| `[ FILE1 -ef FILE2 ]` | Same files |
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### Example
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```bash
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# String
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if [ -z "$string" ]; then
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echo "String is empty"
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elsif [ -n "$string" ]; then
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echo "String is not empty"
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fi
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```
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```bash
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# Combinations
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if [ X ] && [ Y ]; then
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...
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fi
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```
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```bash
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# Regex
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if [[ "A" =~ "." ]]
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```
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```bash
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if (( $a < $b ))
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```
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```bash
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if [ -e "file.txt" ]; then
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echo "file exists"
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fi
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```
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Arrays
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------
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### Defining arrays
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```bash
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Fruits=('Apple' 'Banana' 'Orange')
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```
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```bash
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Fruits[0]="Apple"
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Fruits[1]="Banana"
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Fruits[2]="Orange"
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```
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### Working with arrays
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```bash
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echo ${Fruits[0]} # Element #0
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echo ${Fruits[@]} # All elements, space-separated
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echo ${#Fruits[@]} # Number of elements
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echo ${#Fruits} # String length of the 1st element
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echo ${#Fruits[3]} # String length of the Nth element
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echo ${Fruits[@]:3:2} # Range (from position 3, length 2)
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```
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### Operations
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```bash
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Fruits=("${Fruits[@]}" "Watermelon") # Push
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Fruits=( ${Fruits[@]/Ap*/} ) # Remove by regex match
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unset Fruits[2] # Remove one item
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Fruits=("${Fruits[@]}") # Duplicate
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Fruits=("${Fruits[@]}" "${Veggies[@]}") # Concatenate
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lines=(`cat "logfile"`) # Read from file
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```
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### Iteration
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```bash
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for i in "${arrayName[@]}"; do
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echo $i
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done
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```
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Options
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-------
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### Options
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```bash
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set -o noclobber # Avoid overlay files (echo "hi" > foo)
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set -o errexit # Used to exit upon error, avoiding cascading errors
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set -o pipefail # Unveils hidden failures
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set -o nounset # Exposes unset variables
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```
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### Glob options
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```bash
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set -o nullglob # Non-matching globs are removed ('*.foo' => '')
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set -o failglob # Non-matching globs throw errors
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set -o nocaseglob # Case insensitive globs
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set -o globdots # Wildcards match dotfiles ("*.sh" => ".foo.sh")
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set -o globstar # Allow ** for recursive matches ('lib/**/*.rb' => 'lib/a/b/c.rb')
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```
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Set `GLOBIGNORE` as a colon-separated list of patterns to be removed from glob
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matches.
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Miscellaneous
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-------------
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### Numeric calculations
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```bash
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$((a + 200)) # Add 200 to $a
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```
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```bash
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$((RANDOM%=200)) # Random number 0..200
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```
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### Subshells
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```bash
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(cd somedir; echo "I'm now in $PWD")
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pwd # still in first directory
|
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```
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|
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### Redirection
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||||
|
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```bash
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python hello.py > output.txt # stdout to (file)
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python hello.py >> output.txt # stdout to (file), append
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python hello.py 2> error.log # stderr to (file)
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python hello.py 2>&1 # stderr to stdout
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python hello.py 2>/dev/null # stderr to (null)
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```
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```bash
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python hello.py < foo.txt
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```
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|
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### Inspecting commands
|
||||
|
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```bash
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command -V cd
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#=> "cd is a function/alias/whatever"
|
||||
```
|
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|
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### Trap errors
|
||||
|
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```bash
|
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trap 'echo Error at about $LINENO' ERR
|
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```
|
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|
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or
|
||||
|
||||
```bash
|
||||
traperr() {
|
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echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}"
|
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}
|
||||
|
||||
set -o errtrace
|
||||
trap traperr ERR
|
||||
```
|
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|
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### Case/switch
|
||||
|
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```bash
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case "$1" in
|
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start | up)
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vagrant up
|
||||
;;
|
||||
|
||||
*)
|
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echo "Usage: $0 {start|stop|ssh}"
|
||||
;;
|
||||
esac
|
||||
```
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|
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### Source relative
|
||||
|
||||
```bash
|
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source "${0%/*}/../share/foo.sh"
|
||||
```
|
||||
|
||||
### printf
|
||||
|
||||
```bash
|
||||
printf "Hello %s, I'm %s" Sven Olga
|
||||
#=> "Hello Sven, I'm Olga
|
||||
```
|
||||
|
||||
### Directory of script
|
||||
|
||||
```bash
|
||||
DIR="${0%/*}"
|
||||
```
|
||||
|
||||
### Getting options
|
||||
|
||||
```bash
|
||||
while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in
|
||||
-V | --version )
|
||||
echo $version
|
||||
exit
|
||||
;;
|
||||
-s | --string )
|
||||
shift; string=$1
|
||||
;;
|
||||
-f | --flag )
|
||||
flag=1
|
||||
;;
|
||||
esac; shift; done
|
||||
if [[ "$1" == '--' ]]; then shift; fi
|
||||
```
|
||||
|
||||
### Heredoc
|
||||
|
||||
```sh
|
||||
cat <<END
|
||||
hello world
|
||||
END
|
||||
```
|
||||
|
||||
### Reading input
|
||||
|
||||
```bash
|
||||
echo -n "Proceed? [y/n]: "
|
||||
read ans
|
||||
echo $ans
|
||||
```
|
||||
|
||||
```bash
|
||||
read -n 1 ans # Just one character
|
||||
```
|
||||
|
||||
### Process IDs
|
||||
|
||||
| `$?` | PID of last foreground task |
|
||||
| `$!` | PID of last background task |
|
||||
| `$$` | PID of shell |
|
||||
|
||||
See [Special parameters](http://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables).
|
||||
|
||||
## Also see
|
||||
{: .-one-column}
|
||||
|
||||
* [Bash-hackers wiki](http://wiki.bash-hackers.org/) _(bash-hackers.org)_
|
||||
* [Shell vars](http://wiki.bash-hackers.org/syntax/shellvars) _(bash-hackers.org)_
|
||||
* [Learn bash in y minutes](https://learnxinyminutes.com/docs/bash/) _(learnxinyminutes.com)_
|
||||
|
|
|
|||
575
sh.md
575
sh.md
|
|
@ -1,575 +0,0 @@
|
|||
---
|
||||
title: Bash scripting
|
||||
category: CLI
|
||||
layout: 2017/sheet
|
||||
tags: [Featured]
|
||||
---
|
||||
|
||||
Getting started
|
||||
---------------
|
||||
{: .-three-column}
|
||||
|
||||
### Example
|
||||
|
||||
```bash
|
||||
#!/usr/bin/env bash
|
||||
|
||||
NAME="John"
|
||||
echo "Hello $NAME!"
|
||||
```
|
||||
|
||||
### Variables
|
||||
|
||||
```bash
|
||||
NAME="John"
|
||||
echo $NAME
|
||||
echo "$NAME"
|
||||
echo "${NAME}!"
|
||||
```
|
||||
|
||||
### String quotes
|
||||
|
||||
```bash
|
||||
NAME="John"
|
||||
echo "Hi $NAME" #=> Hi John
|
||||
echo 'Hi $NAME' #=> Hi $NAME
|
||||
```
|
||||
|
||||
### Shell execution
|
||||
|
||||
```bash
|
||||
echo "I'm in $(pwd)"
|
||||
echo "I'm in `pwd`"
|
||||
# Same
|
||||
```
|
||||
|
||||
See [Command substitution](http://wiki.bash-hackers.org/syntax/expansion/cmdsubst)
|
||||
|
||||
### Conditional execution
|
||||
|
||||
```bash
|
||||
git commit && git push
|
||||
git commit || echo "Commit failed"
|
||||
```
|
||||
|
||||
### Functions
|
||||
{: id='functions-example'}
|
||||
|
||||
```bash
|
||||
get_name() {
|
||||
echo "John"
|
||||
}
|
||||
|
||||
echo "You are $(get_name)"
|
||||
```
|
||||
|
||||
See: [Functions](#functions)
|
||||
|
||||
### Conditionals
|
||||
{: id='conditionals-example'}
|
||||
|
||||
```bash
|
||||
if [ -z "$string" ]; then
|
||||
echo "String is empty"
|
||||
elsif [ -n "$string" ]; then
|
||||
echo "String is not empty"
|
||||
fi
|
||||
```
|
||||
|
||||
See: [Conditionals](#conditionals)
|
||||
|
||||
### Strict mode
|
||||
|
||||
```bash
|
||||
set -euo pipefail
|
||||
IFS=$'\n\t'
|
||||
```
|
||||
|
||||
See: [Unofficial bash strict mode](http://redsymbol.net/articles/unofficial-bash-strict-mode/)
|
||||
|
||||
### Brace expansion
|
||||
|
||||
```bash
|
||||
echo {A,B}.js
|
||||
```
|
||||
|
||||
| `{A,B}` | Same as `A B` |
|
||||
| `{A,B}.js` | Same as `A.js B.js` |
|
||||
| `{1..5}` | Same as `1 2 3 4 5` |
|
||||
|
||||
See: [Brace expansion](http://wiki.bash-hackers.org/syntax/expansion/brace)
|
||||
|
||||
|
||||
Parameter expansions
|
||||
--------------------
|
||||
{: .-three-column}
|
||||
|
||||
### Basics
|
||||
|
||||
```bash
|
||||
name="John"
|
||||
echo ${name}
|
||||
echo ${name/J/j} #=> "john" (substitution)
|
||||
echo ${name:0:2} #=> "jo" (slicing)
|
||||
echo ${food:-Cake} #=> $food or "Cake"
|
||||
```
|
||||
|
||||
```bash
|
||||
length=2
|
||||
echo ${name:0:length} #=> "jo"
|
||||
```
|
||||
|
||||
See: [Parameter expansion](http://wiki.bash-hackers.org/syntax/pe)
|
||||
|
||||
```bash
|
||||
STR="/path/to/foo.cpp"
|
||||
echo ${STR%.cpp} # /path/to/foo
|
||||
echo ${STR%.cpp}.o # /path/to/foo.o
|
||||
|
||||
echo ${STR##*.} # cpp (extension)
|
||||
echo ${STR##*/} # foo.cpp (basepath)
|
||||
|
||||
echo ${STR#*/} # path/to/foo.cpp
|
||||
echo ${STR##*/} # foo.cpp
|
||||
|
||||
echo ${STR/foo/bar} # /path/to/bar.cpp
|
||||
```
|
||||
|
||||
```bash
|
||||
STR="Hello world"
|
||||
echo ${STR:6:5} # "world"
|
||||
echo ${STR:-5:5} # "world"
|
||||
```
|
||||
|
||||
```bash
|
||||
SRC="/path/to/foo.cpp"
|
||||
BASE=${STR##*/} #=> "foo.cpp" (basepath)
|
||||
DIR=${SRC%$BASE} #=> "/path/to" (dirpath)
|
||||
```
|
||||
|
||||
### Substitution
|
||||
|
||||
| Code | Description |
|
||||
| --- | --- |
|
||||
| `${FOO%suffix}` | Remove suffix |
|
||||
| `${FOO#prefix}` | Remove prefix |
|
||||
| --- | --- |
|
||||
| `${FOO%%suffix}` | Remove long suffix |
|
||||
| `${FOO##prefix}` | Remove long prefix |
|
||||
| --- | --- |
|
||||
| `${FOO/from/to}` | Replace first match |
|
||||
| `${FOO//from/to}` | Replace all |
|
||||
| --- | --- |
|
||||
| `${FOO/%from/to}` | Replace suffix |
|
||||
| `${FOO/#from/to}` | Replace prefix |
|
||||
|
||||
### Substrings
|
||||
|
||||
| `${FOO:0:3}` | Substring _(position, length)_ |
|
||||
| `${FOO:-3:3}` | Substring from the right |
|
||||
|
||||
### Length
|
||||
|
||||
| `${#FOO}` | Length of `$FOO` |
|
||||
|
||||
### Default values
|
||||
|
||||
| `${FOO:-val}` | `$FOO`, or `val` if not set |
|
||||
| `${FOO:=val}` | Set `$FOO` to `val` if not set |
|
||||
| `${FOO:+val}` | `val` if `$FOO` is set |
|
||||
| `${FOO:?message}` | Show error message ande xit if `$FOO` is not set |
|
||||
|
||||
The `:` is optional (eg, `${FOO=word}` works)
|
||||
|
||||
Loops
|
||||
-----
|
||||
{: .-three-column}
|
||||
|
||||
### Basic for loop
|
||||
|
||||
```bash
|
||||
for i in /etc/rc.*; do
|
||||
echo $i
|
||||
done
|
||||
```
|
||||
|
||||
### Ranges
|
||||
|
||||
```bash
|
||||
for i in {1..5}; do
|
||||
echo "Welcome $i"
|
||||
done
|
||||
```
|
||||
|
||||
### Reading lines
|
||||
|
||||
```bash
|
||||
cat file.txt | while read line; do
|
||||
echo $line
|
||||
done
|
||||
```
|
||||
|
||||
### Forever
|
||||
|
||||
```bash
|
||||
while true; do
|
||||
···
|
||||
done
|
||||
```
|
||||
|
||||
Functions
|
||||
---------
|
||||
{: .-three-column}
|
||||
|
||||
### Defining functions
|
||||
|
||||
```bash
|
||||
myfunc() {
|
||||
echo "hello $1"
|
||||
}
|
||||
```
|
||||
|
||||
```bash
|
||||
# Same as above (alternate syntax)
|
||||
function myfunc() {
|
||||
echo "hello $1"
|
||||
}
|
||||
```
|
||||
|
||||
```bash
|
||||
myfunc "John"
|
||||
```
|
||||
|
||||
### Returning values
|
||||
|
||||
```bash
|
||||
myfunc() {
|
||||
local myresult='some value'
|
||||
echo $myresult
|
||||
}
|
||||
```
|
||||
|
||||
```bash
|
||||
result=$(myfunc)
|
||||
```
|
||||
|
||||
### Raising errors
|
||||
|
||||
```bash
|
||||
myfunc() {
|
||||
return 1
|
||||
}
|
||||
```
|
||||
|
||||
```bash
|
||||
if myfunc; then
|
||||
echo "success"
|
||||
else
|
||||
echo "failure"
|
||||
fi
|
||||
```
|
||||
|
||||
### Arguments
|
||||
|
||||
| Expression | Description |
|
||||
| --- | --- |
|
||||
| `$#` | Number of arguments |
|
||||
| `$*` | All arguments |
|
||||
| `$@` | All arguments, starting from first |
|
||||
| `$1` | First argument |
|
||||
|
||||
See [Special parameters](http://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables).
|
||||
|
||||
Conditionals
|
||||
------------
|
||||
{: .-three-column}
|
||||
|
||||
### Conditions
|
||||
|
||||
| Condition | Description |
|
||||
| --- | --- |
|
||||
| `[ -z STRING ]` | Empty string |
|
||||
| `[ -n STRING ]` | Not empty string |
|
||||
| --- | --- |
|
||||
| `[ NUM -eq NUM ]` | Equal |
|
||||
| `[ NUM -ne NUM ]` | Not equal |
|
||||
| `[ NUM -lt NUM ]` | Less than |
|
||||
| `[ NUM -le NUM ]` | Less than or equal |
|
||||
| `[ NUM -gt NUM ]` | Greater than |
|
||||
| `[ NUM -ge NUM ]` | Greater than or equal |
|
||||
| --- | --- |
|
||||
| `[[ STRING =~ STRING ]]` | Regexp |
|
||||
| --- | --- |
|
||||
| `(( NUM < NUM ))` | Numeric conditions |
|
||||
|
||||
| Condition | Description |
|
||||
| --- | --- |
|
||||
| `[ -o noclobber ]` | If OPTIONNAME is enabled |
|
||||
| --- | --- |
|
||||
| `[ ! EXPR ]` | Not |
|
||||
| `[ X ] && [ Y ]` | And |
|
||||
| `[ X ] || [ Y ]` | Or |
|
||||
|
||||
### File conditions
|
||||
|
||||
| Condition | Description |
|
||||
| --- | --- |
|
||||
| `[ -e FILE ]` | Exists |
|
||||
| `[ -r FILE ]` | Readable |
|
||||
| `[ -h FILE ]` | Symlink |
|
||||
| `[ -d FILE ]` | Directory |
|
||||
| `[ -w FILE ]` | Writable |
|
||||
| `[ -s FILE ]` | Size is > 0 bytes |
|
||||
| `[ -f FILE ]` | File |
|
||||
| `[ -x FILE ]` | Executable |
|
||||
| --- | --- |
|
||||
| `[ FILE1 -nt FILE2 ]` | 1 is more recent than 2 |
|
||||
| `[ FILE1 -ot FILE2 ]` | 2 is more recent than 1 |
|
||||
| `[ FILE1 -ef FILE2 ]` | Same files |
|
||||
|
||||
### Example
|
||||
|
||||
```bash
|
||||
# String
|
||||
if [ -z "$string" ]; then
|
||||
echo "String is empty"
|
||||
elsif [ -n "$string" ]; then
|
||||
echo "String is not empty"
|
||||
fi
|
||||
```
|
||||
|
||||
```bash
|
||||
# Combinations
|
||||
if [ X ] && [ Y ]; then
|
||||
...
|
||||
fi
|
||||
```
|
||||
|
||||
```bash
|
||||
# Regex
|
||||
if [[ "A" =~ "." ]]
|
||||
```
|
||||
|
||||
```bash
|
||||
if (( $a < $b ))
|
||||
```
|
||||
|
||||
```bash
|
||||
if [ -e "file.txt" ]; then
|
||||
echo "file exists"
|
||||
fi
|
||||
```
|
||||
|
||||
Arrays
|
||||
------
|
||||
|
||||
### Defining arrays
|
||||
|
||||
```bash
|
||||
Fruits=('Apple' 'Banana' 'Orange')
|
||||
```
|
||||
|
||||
```bash
|
||||
Fruits[0]="Apple"
|
||||
Fruits[1]="Banana"
|
||||
Fruits[2]="Orange"
|
||||
```
|
||||
|
||||
### Working with arrays
|
||||
|
||||
```bash
|
||||
echo ${Fruits[0]} # Element #0
|
||||
echo ${Fruits[@]} # All elements, space-separated
|
||||
echo ${#Fruits[@]} # Number of elements
|
||||
echo ${#Fruits} # String length of the 1st element
|
||||
echo ${#Fruits[3]} # String length of the Nth element
|
||||
echo ${Fruits[@]:3:2} # Range (from position 3, length 2)
|
||||
```
|
||||
|
||||
### Operations
|
||||
|
||||
```bash
|
||||
Fruits=("${Fruits[@]}" "Watermelon") # Push
|
||||
Fruits=( ${Fruits[@]/Ap*/} ) # Remove by regex match
|
||||
unset Fruits[2] # Remove one item
|
||||
Fruits=("${Fruits[@]}") # Duplicate
|
||||
Fruits=("${Fruits[@]}" "${Veggies[@]}") # Concatenate
|
||||
lines=(`cat "logfile"`) # Read from file
|
||||
```
|
||||
|
||||
### Iteration
|
||||
|
||||
```bash
|
||||
for i in "${arrayName[@]}"; do
|
||||
echo $i
|
||||
done
|
||||
```
|
||||
|
||||
Options
|
||||
-------
|
||||
|
||||
### Options
|
||||
|
||||
```bash
|
||||
set -o noclobber # Avoid overlay files (echo "hi" > foo)
|
||||
set -o errexit # Used to exit upon error, avoiding cascading errors
|
||||
set -o pipefail # Unveils hidden failures
|
||||
set -o nounset # Exposes unset variables
|
||||
```
|
||||
|
||||
### Glob options
|
||||
|
||||
```bash
|
||||
set -o nullglob # Non-matching globs are removed ('*.foo' => '')
|
||||
set -o failglob # Non-matching globs throw errors
|
||||
set -o nocaseglob # Case insensitive globs
|
||||
set -o globdots # Wildcards match dotfiles ("*.sh" => ".foo.sh")
|
||||
set -o globstar # Allow ** for recursive matches ('lib/**/*.rb' => 'lib/a/b/c.rb')
|
||||
```
|
||||
|
||||
Set `GLOBIGNORE` as a colon-separated list of patterns to be removed from glob
|
||||
matches.
|
||||
|
||||
Miscellaneous
|
||||
-------------
|
||||
|
||||
### Numeric calculations
|
||||
|
||||
```bash
|
||||
$((a + 200)) # Add 200 to $a
|
||||
```
|
||||
|
||||
```bash
|
||||
$((RANDOM%=200)) # Random number 0..200
|
||||
```
|
||||
|
||||
### Subshells
|
||||
|
||||
```bash
|
||||
(cd somedir; echo "I'm now in $PWD")
|
||||
pwd # still in first directory
|
||||
```
|
||||
|
||||
### Redirection
|
||||
|
||||
```bash
|
||||
python hello.py > output.txt # stdout to (file)
|
||||
python hello.py >> output.txt # stdout to (file), append
|
||||
python hello.py 2> error.log # stderr to (file)
|
||||
python hello.py 2>&1 # stderr to stdout
|
||||
python hello.py 2>/dev/null # stderr to (null)
|
||||
```
|
||||
|
||||
```bash
|
||||
python hello.py < foo.txt
|
||||
```
|
||||
|
||||
### Inspecting commands
|
||||
|
||||
```bash
|
||||
command -V cd
|
||||
#=> "cd is a function/alias/whatever"
|
||||
```
|
||||
|
||||
### Trap errors
|
||||
|
||||
```bash
|
||||
trap 'echo Error at about $LINENO' ERR
|
||||
```
|
||||
|
||||
or
|
||||
|
||||
```bash
|
||||
traperr() {
|
||||
echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}"
|
||||
}
|
||||
|
||||
set -o errtrace
|
||||
trap traperr ERR
|
||||
```
|
||||
|
||||
### Case/switch
|
||||
|
||||
```bash
|
||||
case "$1" in
|
||||
start | up)
|
||||
vagrant up
|
||||
;;
|
||||
|
||||
*)
|
||||
echo "Usage: $0 {start|stop|ssh}"
|
||||
;;
|
||||
esac
|
||||
```
|
||||
|
||||
### Source relative
|
||||
|
||||
```bash
|
||||
source "${0%/*}/../share/foo.sh"
|
||||
```
|
||||
|
||||
### printf
|
||||
|
||||
```bash
|
||||
printf "Hello %s, I'm %s" Sven Olga
|
||||
#=> "Hello Sven, I'm Olga
|
||||
```
|
||||
|
||||
### Directory of script
|
||||
|
||||
```bash
|
||||
DIR="${0%/*}"
|
||||
```
|
||||
|
||||
### Getting options
|
||||
|
||||
```bash
|
||||
while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in
|
||||
-V | --version )
|
||||
echo $version
|
||||
exit
|
||||
;;
|
||||
-s | --string )
|
||||
shift; string=$1
|
||||
;;
|
||||
-f | --flag )
|
||||
flag=1
|
||||
;;
|
||||
esac; shift; done
|
||||
if [[ "$1" == '--' ]]; then shift; fi
|
||||
```
|
||||
|
||||
### Heredoc
|
||||
|
||||
```sh
|
||||
cat <<END
|
||||
hello world
|
||||
END
|
||||
```
|
||||
|
||||
### Reading input
|
||||
|
||||
```bash
|
||||
echo -n "Proceed? [y/n]: "
|
||||
read ans
|
||||
echo $ans
|
||||
```
|
||||
|
||||
```bash
|
||||
read -n 1 ans # Just one character
|
||||
```
|
||||
|
||||
### Process IDs
|
||||
|
||||
| `$?` | PID of last foreground task |
|
||||
| `$!` | PID of last background task |
|
||||
| `$$` | PID of shell |
|
||||
|
||||
See [Special parameters](http://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables).
|
||||
|
||||
## Also see
|
||||
{: .-one-column}
|
||||
|
||||
* [Bash-hackers wiki](http://wiki.bash-hackers.org/) _(bash-hackers.org)_
|
||||
* [Shell vars](http://wiki.bash-hackers.org/syntax/shellvars) _(bash-hackers.org)_
|
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* [Learn bash in y minutes](https://learnxinyminutes.com/docs/bash/) _(learnxinyminutes.com)_
|
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Reference in New Issue