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2024-07-23

Bash - cheat sheet

Contents

• Arguments
• Conditionals
• Colors

Arguments

variable	description
$0	name of the script
$1	first argument
$2	second argument
$<n>	<nth> argument, where n > 0
$@	all arguments as one string
$#	count of arguments

Example

#!/bin/bash

echo script started with $# args: $@

for arg in "$@"; do
    echo "$arg"
done
# $ ./script.sh --config=test --verbose 1 2
# script started with 4 args: --config=test --verbose 1 2
# --config=test
# --verbose
# 1
# 2

Conditionals

if [[ <CONDITION> ]]; then
  ...
elif [[ <CONDITION> ]]; then
  ...
else
  ...
fi

condition	description
"$VAR" == "STRING"	compare content of env var with string
-z "$VAR"	test if string length is zero
-n "$VAR"	test if string length is not zero
-f "$VAR"	test if regular file exist

Colors

Print the rainbow: for (( i = 0; i < 39; i++ )); do echo -ne "\033[0;"$i"m Normal: (0;$i); \033[1;"$i"m Light: (1;$i)\t\t\t\t\t"; done¹

Prefix \033 is preferrable over \x1b and \e, as its supported on more platforms.