bash hash generator function

hashgen-function

# Simple Bash Hash Generator
#
# Author: Chris Hager <chris@linuxuser.at>
#
# Put the `hashgen` method in your `.functions` file and source it from your `.bash_profile`
#
# Usage: hashgen [type] [#chars]
#
# Optional argument `type`:
# 
#     n .... numbers
#     x .... a-f
#     xn ... a-f, 0-9
#     xX ... a-f, A-F
#     xXn .. a-f, A-F, 0-9
#     a .... a-z
#     an ... a-z, 0-9
#     aA ... a-z, A-Z
#     aAn .. a-z, A-Z, 0-9
#
# Examples:
#
#     $ hashgen
#     ccee24b6
#
#     $ hashgen 20
#     c1df84a25f42af24c81c
#
#     $ hashgen aAn 20
#     VcmTRAiv4LVDiraxSCna
#
function hashgen() {
    CHARS=8
    TYPES=(n x xn xX xXn a an aA aAn)
    TYPE=xn  # default: lower case a-f + 0-9
    RE_NUM='^[0-9]+$'

    for ARG in "$@"
    do
        if [[ $ARG =~ $RE_NUM ]]; then
            CHARS=$ARG
        else
            case "${TYPES[@]}" in *"$ARG"*) TYPE=$ARG ;; esac
        fi
    done

    #echo "type: $TYPE, chars: $CHARS"
    case $TYPE in
        "aAn"*) cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w $CHARS | head -n 1 ;;
        "aA"*)  cat /dev/urandom | tr -dc 'a-zA-Z'    | fold -w $CHARS | head -n 1 ;;
        "an"*)  cat /dev/urandom | tr -dc 'a-z0-9'    | fold -w $CHARS | head -n 1 ;;
        "a"*)   cat /dev/urandom | tr -dc 'a-z'       | fold -w $CHARS | head -n 1 ;;
        "xXn"*) cat /dev/urandom | tr -dc 'a-fA-F0-9' | fold -w $CHARS | head -n 1 ;;
        "xX"*)  cat /dev/urandom | tr -dc 'a-fA-F'    | fold -w $CHARS | head -n 1 ;;
        "xn"*)  cat /dev/urandom | tr -dc 'a-f0-9'    | fold -w $CHARS | head -n 1 ;;
        "x"*)   cat /dev/urandom | tr -dc 'a-f'       | fold -w $CHARS | head -n 1 ;;
        "n"*)   cat /dev/urandom | tr -dc '0-9'       | fold -w $CHARS | head -n 1 ;;
    esac
}