Bash

Bash is the GNU Project's shell—the Bourne Again SHell. This is an sh-compatible shell that incorporates useful features from the Korn shell (ksh) and the C shell (csh). It is intended to conform to the IEEE POSIX P1003.2/ISO 9945.2 Shell and Tools standard. It offers functional improvements over sh for both programming and interactive use. In addition, most sh scripts can be run by Bash without modification.¹

Examples

Get Script Location¹

Simple example

SCRIPT_DIR=$(readlink -f $(dirname "${BASH_SOURCE[0]}"))

Complex example

SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )

Check for Environment Variable

Bash 4.2+Older Bash

if [ ! -v MY_VAR ]; then
    echo "MY_VAR is not defined."
else
    echo "MY_VAR is defined."
fi

Essentially checks for an empty string

if [ -z "${MY_VAR}" ]; then
    echo "MY_VAR is not defined."
else
    echo "MY_VAR is defined."
fi

Check Script Arguments

if [ "$#" -eq 0 ]; then
    echo "No arguments provided."
    exit 1
else
    echo "The script received the following arguments:"
    for arg in "$@"; do
        echo "- $arg"
    done
fi

Terminal Colors

tput commands

BLACK=$(tput setaf 0)
RED=$(tput setaf 1)
GREEN=$(tput setaf 2)
YELLOW=$(tput setaf 3)
BLUE=$(tput setaf 4)
MAGENTA=$(tput setaf 5)
CYAN=$(tput setaf 6)
WHITE=$(tput setaf 7)
BOLD=$(tput bold)
REVERSE=$(tput rev)
RESET=$(tput sgr0)

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1. How do I get the directory where a Bash script is located from within the script itself? ↩↩