bash-snippets

shebang
Functions
Parsing command line arguments
Get the current script directory
For Loop
Check how a script was called

shebang

#!/usr/bin/env bash

Functions

# Define a function.
function quit {
   exit
}

# Call the function.
quit

# Define a function that takes a paramter.
function printarg {
    echo $1
}

# Call the function with an argument.
printarg "Hello, world!"

Parsing command line arguments

for i in "$@"
do
case $i in
    -e=*|--extension=*)
    eval EXTENSION="${i#*=}"
    shift # past argument=value
    ;;
    -s=*|--searchpath=*)
    eval SEARCHPATH="${i#*=}"
    shift # past argument=value
    ;;
    -l=*|--lib=*)
    eval LIBPATH="${i#*=}"
    shift # past argument=value
    ;;
    --default)
    DEFAULT=YES
    shift # past argument with no value
    ;;
    *)
    # unknown option
    ;;
esac
done

Get the current script directory

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"

For Loop

for i in {0..5}; do
   echo $i
done
# Prints out:
# 0
# 1
# 2
# 3
# 4
# 5

Checking if script was called directly

Check if a scipt was called vs. source'd by another script. Analagous to if __name__ == "__main__": in Python.

if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
    ...
fi

The above if condition will hit if the script is called directly, i.e. ./my_script.sh or bash my_script.sh. However, it will not be called if the script is source'd by another script, e.g.

# contents of some_other_script.sh

source my_script.sh

echo "doing other things..."

./some_other_script.sh
# the if condition will not hit