converts a string to lower characters

strtoupper.bash

# converts a string to lower characters
# @param string input

function strtoupper()
{   
    [ -z "$1" ] && return 1
    printf "%s\\n" "$@" | tr 'abcdefghijklmnopqrstuvwxyz' 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' # tr '[:upper:]' '[:lower:]'
}