pure-bash-bible/README.md

pure bash

A collection of pure bash alternatives to external processes.

• Getting the terminal size (in a script).
• Convert a hex color to RGB
• Convert an RGB color to hex.
• printf as a date replacement.
• dirname

Getting the terminal size (in a script).

This is handy when writing scripts in pure bash and stty/tput can’t be called.

get_term_size() {
    # Usage: get_term_size

    # (:;:) is a micro sleep to ensure the variables are
    # exported immediately.
    shopt -s checkwinsize; (:;:)
    printf '%s\n' "$LINES $COLUMNS"
}

Convert a hex color to RGB

hex_to_rgb() {
    # Usage: hex_to_rgb "#FFFFFF"
    ((r=16#${1:1:2}))
    ((g=16#${1:3:2}))
    ((b=16#${1:5:6}))

    printf '%s\n' "$r $g $b"
}

Convert an RGB color to hex.

rgb_to_hex() {
    # Usage: rgb_to_hex "r" "g" "b"
    printf '#%02x%02x%02x\n' "$1" "$2" "$3"
}

printf as a date replacement.

Bash’s printf has a built-in method of getting the date which we can use in place of the date command in a lot of cases.

NOTE: Requires bash4+

date() {
    # Usage: date "format"
    # See: 'man strftime' for format.
    printf "%($1)T\\n"
}

dirname

Extract the directory from a file path.

dirname() {
    # Usage: dirname "path"
    printf ‘%s\n’ "${1%/*}/"
}