feat(unitproc/bkshuf):Exit early if stdout not being read

[BK-2020-03.git] / unitproc / bkt-read_stdin

#!/usr/bin/env bash
# Desc: Reads stdin

yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
read_stdin() {
    # Desc: Consumes stdin; outputs as stdout lines
    # Input: stdin (consumes)
    # Output: stdout  (newline delimited)
    #         return  0  stdin read
    #         return  1  stdin not present
    # Example: printf "foo\nbar\n" | read_stdin
    # Depends: GNU bash (version 5.1.16), GNU Coreutils 8.32 (cat)
    # Version: 0.1.1
    # Attrib: Steven Baltakatei Sandoval (2024-01-29). reboil.com
    local input_stdin output;

    # Store stdin
    if [[ -p /dev/stdin ]]; then
        input_stdin="$(cat -)" || {
            echo "FATAL:Error reading stdin." 1>&2; return 1; };
    else
        return 1;
    fi; 
    
    # Store as output array elements
    ## Read in stdin
    if [[ -n $input_stdin ]]; then
        while read -r line; do
            output+=("$line");
        done < <(printf "%s\n" "$input_stdin") || {
            echo "FATAL:Error parsing stdin."; return 1; };
    fi;

    # Print to stdout
    printf "%s\n" "${output[@]}";

    return 0;
}; # read stdin to stdout lines

yell "WARNING:This is a Bash function definition for read_stdin.";