Add multi range brace expansion to bash.md (#2071)
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Iftakhar Husan
Rico Sta. Cruz
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bash.md
106
bash.md
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@ -14,11 +14,12 @@ keywords:
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- Command substitution
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---
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Getting started
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---------------
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## Getting started
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{: .-three-column}
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### Introduction
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{: .-intro}
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This is a quick reference to getting started with Bash scripting.
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@ -44,6 +45,7 @@ echo $name # see below
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echo "$name"
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echo "${name}!"
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```
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Generally quote your variables unless they contain wildcards to expand or command fragments.
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```bash
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@ -78,6 +80,7 @@ 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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@ -91,6 +94,7 @@ echo "You are $(get_name)"
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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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@ -118,17 +122,17 @@ See: [Unofficial bash strict mode](http://redsymbol.net/articles/unofficial-bash
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echo {A,B}.js
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```
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| Expression | Description |
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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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| Expression | Description |
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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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| <code>{{1..3},{7..9}}</code> | Same as `1 2 3 7 8 9` |
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See: [Brace expansion](https://web.archive.org/web/20230207192110/https://wiki.bash-hackers.org/syntax/expansion/brace)
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## Parameter expansions
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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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@ -247,8 +251,8 @@ echo "${str^^}" #=> "HELLO WORLD!" (all uppercase)
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Omitting the `:` removes the (non)nullity checks, e.g. `${foo-val}` expands to `val` if unset otherwise `$foo`.
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Loops
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-----
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## Loops
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{: .-three-column}
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### Basic for loop
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@ -299,8 +303,8 @@ while true; do
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done
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```
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Functions
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---------
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## Functions
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{: .-three-column}
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### Defining functions
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@ -353,21 +357,21 @@ fi
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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 positional arguments (as a single word) |
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| `$@` | All positional arguments (as separate strings) |
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| `$1` | First argument |
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| `$_` | Last argument of the previous command |
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| Expression | Description |
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| ---------- | ---------------------------------------------- |
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| `$#` | Number of arguments |
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| `$*` | All positional arguments (as a single word) |
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| `$@` | All positional arguments (as separate strings) |
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| `$1` | First argument |
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| `$_` | Last argument of the previous command |
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**Note**: `$@` and `$*` must be quoted in order to perform as described.
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Otherwise, they do exactly the same thing (arguments as separate strings).
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See [Special parameters](https://web.archive.org/web/20230318164746/https://wiki.bash-hackers.org/syntax/shellvars#special_parameters_and_shell_variables).
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Conditionals
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------------
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## Conditionals
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{: .-three-column}
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### Conditions
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@ -375,7 +379,7 @@ Conditionals
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Note that `[[` is actually a command/program that returns either `0` (true) or `1` (false). Any program that obeys the same logic (like all base utils, such as `grep(1)` or `ping(1)`) can be used as condition, see examples.
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| Condition | Description |
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| --- | --- |
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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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| `[[ STRING == STRING ]]` | Equal |
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@ -405,7 +409,7 @@ Note that `[[` is actually a command/program that returns either `0` (true) or `
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### File conditions
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| Condition | Description |
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| --- | --- |
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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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@ -461,8 +465,7 @@ if [[ -e "file.txt" ]]; then
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fi
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```
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Arrays
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------
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## Arrays
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### Defining arrays
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@ -509,8 +512,8 @@ for i in "${arrayName[@]}"; do
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done
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```
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Dictionaries
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------------
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## Dictionaries
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{: .-three-column}
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### Defining
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@ -556,8 +559,7 @@ for key in "${!sounds[@]}"; do
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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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### Options
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@ -581,8 +583,7 @@ shopt -s globstar # Allow ** for recursive matches ('lib/**/*.rb' => 'lib/a/b
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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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History
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-------
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## History
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### Commands
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@ -625,9 +626,7 @@ History
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`!!` can be replaced with any valid expansion i.e. `!cat`, `!-2`, `!42`, etc.
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Miscellaneous
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-------------
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## Miscellaneous
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### Numeric calculations
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@ -640,7 +639,7 @@ $(($RANDOM%200)) # Random number 0..199
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```
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```bash
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declare -i count # Declare as type integer
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declare -i count # Declare as type integer
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count+=1 # Increment
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```
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@ -732,18 +731,18 @@ printf '%i+%i=%i\n' 1 2 3 4 5 9
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### Transform strings
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| Command option | Description |
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| ------------------ | --------------------------------------------------- |
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| `-c` | Operations apply to characters not in the given set |
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| `-d` | Delete characters |
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| `-s` | Replaces repeated characters with single occurrence |
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| `-t` | Truncates |
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| `[:upper:]` | All upper case letters |
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| `[:lower:]` | All lower case letters |
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| `[:digit:]` | All digits |
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| `[:space:]` | All whitespace |
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| `[:alpha:]` | All letters |
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| `[:alnum:]` | All letters and digits |
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| Command option | Description |
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| -------------- | --------------------------------------------------- |
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| `-c` | Operations apply to characters not in the given set |
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| `-d` | Delete characters |
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| `-s` | Replaces repeated characters with single occurrence |
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| `-t` | Truncates |
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| `[:upper:]` | All upper case letters |
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| `[:lower:]` | All lower case letters |
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| `[:digit:]` | All digits |
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| `[:space:]` | All whitespace |
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| `[:alpha:]` | All letters |
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| `[:alnum:]` | All letters and digits |
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#### Example
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@ -838,10 +837,11 @@ fi
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```
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## Also see
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{: .-one-column}
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* [Bash-hackers wiki](https://web.archive.org/web/20230406205817/https://wiki.bash-hackers.org/) _(bash-hackers.org)_
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* [Shell vars](https://web.archive.org/web/20230318164746/https://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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* [Bash Guide](http://mywiki.wooledge.org/BashGuide) _(mywiki.wooledge.org)_
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* [ShellCheck](https://www.shellcheck.net/) _(shellcheck.net)_
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- [Bash-hackers wiki](https://web.archive.org/web/20230406205817/https://wiki.bash-hackers.org/) _(bash-hackers.org)_
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- [Shell vars](https://web.archive.org/web/20230318164746/https://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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- [Bash Guide](http://mywiki.wooledge.org/BashGuide) _(mywiki.wooledge.org)_
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- [ShellCheck](https://www.shellcheck.net/) _(shellcheck.net)_
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