ULID on shell script. Universally Unique Lexicographically Sortable Identifier. [ULID](https://github.com/ulid/spec)

ulid.sh

#!/bin/sh
# -*- coding:utf-8 posix -*-
# === Initialize shell environment =============================================
#set -u                        # Just stop undefined values.
#set -e                        # Just stop error.
#set -x                        # Debug running command.

umask 0022
export LC_ALL=C
export LANG=C
PATH="$(command -p getconf PATH 2>/dev/null)${PATH+:}${PATH-}"
case $PATH in (:*) PATH=${PATH#?};; esac
export PATH # or PATH="<add dir>${PATH+:}${PATH-}"
export UNIX_STD=2003          # to make HP-UX conform to POSIX

# === Define the functions for printing usage and error message ================
usage_and_exit(){
    cat <<-"USAGE" 1>&2

# About

The ulid.sh is a shell script implimentation of
"Universally Unique Lexicographically Sortable Identifier".
[ULID](https://github.com/ulid/spec).

Bad, this script does not conform to the "Monotonicity" specification.
Therefore, the 80-bit random region is always random.

Also, this script does not get the exact time (milliseconds). This is because
there is no stable way to obtain this with shell commands. However,
you can optionally specify milliseconds.

# Usage

## Command

ulid.sh [Options] [--msec <ms>]

```
$> ulid.sh
   01DNPS05T77C5WY933034FYZYP
```

```
$> i=0; while [ 5 -gt $i ] ; do i=$(( i + 1 )); ./ulid.sh --msec 158598740350$i; done
   01E523EFQDPTDVW5V4AZ6AY1NW
   01E523EFQEY8PDZ1CS95A1QH18
   01E523EFQF7HCPSXJVQ8K15TCV
   01E523EFQG0XBA99T9VVHTW3RB
   01E523EFQH84V9KTYRQN24FHRJ
```

## Options

+ -h |--help |--version
  - help.
+ --msec <ms>
  - Generating at <ms>.

# Version

2022-12-20T23:10:00 0.09 [Latest](https://gist.github.com/search?q=user%3Atd-shi+filename%3A.sh+ulid)

# LICENSE

[CC0(Public domain)](https://creativecommons.org/publicdomain/zero/1.0/legalcode)

# Author

2020 TD

USAGE

    exit 1
}

error_exit() {
    ${2+:} false && echo "${0##*/}: $2" 1>&2

    exit "$1"
}

# === Initialize parameters ====================================================
TIME=0

# === Confirm that the required commands exist =================================
if type hexdump >/dev/null 2>&1 ; then
    genRandom () {
        hexdump -n 16 -e '8/2 " %04x" "\n"' -v /dev/urandom | tr -d " "
    }
elif type od >/dev/null 2>&1 ; then
    genRandom () {
        od -A n -t x2 -N 16 -v /dev/urandom | tr -d " "
    }
else
    error_exit 1 'require command "hexdump" or "od"'
fi
type od >/dev/null 2>&1 || error_exit 1 'require command od'

# === Print usage and exit if one of the help options is set ===================
case "$# ${1:-}" in
    ('1 -h'|'1 --help'|'1 --version') usage_and_exit;;
esac

# === Read options =============================================================
while :; do
    case "${1:-}" in
        (--|-)
            break
            ;;
        (--msec)
            TIME=$(printf '%s' "${2:-}" | tr -Cd "0123456789")
            shift 2
            ;;
        (--*|-*)
            error_exit 1 'Invalid option'
            ;;
        (*)
            break
            ;;
    esac
done

# === Require parameters check =================================================
# === Last parameter ===========================================================
# === Define funcitons =========================================================
unixTimeSec () {
    set -- "$(date -u "+%Y-%m-%d %H:%M:%S")" "$1"
    set -- "${1%% *}" "${1##* }" "$2"
    set -- "${1%%-*}" "${1#*-}" "${2%%:*}" "${2#*:}" "$3"
    set -- "$1" "${2%%-*}" "${2#*-}" "$3" "${4%%:*}" "${4#*:}" "$5"
    set -- "${1}" "${2#0}" "${3#0}" "${4#0}" "${5#0}" "${6#0}" "$7"
    [ "$2" -lt 3 ] && set -- $(($1 - 1)) $(($2 + 12)) "$3" "$4" "$5" "$6" "$7"
    set -- $(( (365 * $1) + ($1 / 4) - ($1 / 100) + ($1 / 400))) $(( (306 * (1 + $2) / 10) - 428 )) "$3" "$4" "$5" "$6" "$7"
    set -- $(( ($1 + $2 + $3 - 719163) * 86400 + $4 * 3600 + $5 * 60 + $6 )) "$7"
    printf "%s%s" "$1" "$2"
}

decodeHex5BaseV4() {
    set -- "${1%???}" "${1#?}" "${1#??}" "${1#???}"
    set -- "0x${1}" "0x${2%??}" "0x${3%?}" "0x${4}"
    set -- "\\1$(($1>>6 & 0x3))$(($1>>3 & 0x7))" "\\1$(($2>>5 & 0x3))$(($2>>2 & 0x7))" "\\1$(($3>>4 & 0x3))$(($3>>1 & 0x7))" "\\1$(($4>>3 & 0x3))$(($4 & 0x7))"
    printf "$1$2$3$4"
}

decode2Hex () {
    set -- "$1" "0" ""
    while [ "$1" -gt 0 ] ; do
        set -- "$(( $1 / 16))" "$(( $1 % 16 ))" "$3"
        set -- "$1" "$2" "\\0$(( ($2>>3) + 6))$(($2 & 0x7))$3"
    done
    printf "$3" | tr ":;<=>?" "abcdef"
}

# === Main routine =============================================================
if [ "_" != "_${TIME}" ] && [ "${TIME}" -gt 0 ]; then
    :
else
    TIME=$(unixTimeSec "000")
fi

set -- "000000000000000$(decode2Hex "${TIME}")" "0000$(genRandom)"
set -- "${1#${1%???????????????}}" "${2#${2%????????????????????}}" # 15, 20
set -- "${1%??????????}" "${1#?????}" "${2%??????????}" "${2#??????????}"
set -- "$1" "${2%?????}" "${2#?????}" "${3%?????}" "${3#?????}" "${4%?????}" "${4#?????}"

ULID=$(while [ $# -gt 0 ] ; do decodeHex5BaseV4 "$1"; shift; done | tr "@ABCDEFGHIJKLMNOPQRSTUVWXYZ\[\\\]^_\`" "0123456789ABCDEFGHJKMNPQRSTVWXYZ")
printf "%s\n" "${ULID#??}"

# === End shell script =========================================================
exit 0