Flexible inputs for Bash scripts

stdin.sh

#!/bin/bash

set -euo pipefail

function process {
    return 0
}

function main {
    mapfile -t inputs < <(echo "${1:-$(</dev/stdin)}")
    for input in "${inputs[@]}"; do
        process "$input" ||
    done
}

if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then
    main "$@"
fi

usage.md

Usage

$ ./stdin.sh $input
$ # or
$ ./stdin.sh <<< $input
$ # or
$ echo $input | ./stdin.sh
$ # or
$ ./stdin.sh  # enter the input(s) and ^D
$ # or
$ ./stdin.sh < inputs.txt
$ # or
$ cat inputs.txt | ./stdin.sh