How can I output null-terminated strings in Awk?

Question

I\'m working on a shell script that will be used by others, and may ingest suspect strings. It\'s based around awk, so as a basic resiliency measure, I want to have awk outp

Answer 1

There are three alternatives:

1. Setting ORS to ASCII zero: Other solutions have awk -vORS=$'\0' but:
   The $'\0' is a construct specific to some shells (bash,zsh).
   So: this command awk -vORS=$'\0' will not work in most older shells.

There is the option to write it as: awk 'BEGIN { ORS = "\0" } ; { print $0 }', but that will not work with most awk versions.

2. Printing (printf) with character \0: awk '{printf( "%s\0", $0)}'

3. Printing directly ASCII 0: awk '{ printf( "%s%c", $0, 0 )}'

Testing all alternatives with this code:

#!/bin/bash

test1(){   # '{printf( "%s%c",$0,0)}'|
    a='awk,mawk,original-awk,busybox awk'
    IFS=',' read -ra line <<<"$a"
    for i in "${line[@]}"; do
        printf "%14.12s %40s" "$i" "$1"
        echo -ne "a\nb\nc\n" |
        $i "$1"|
        od -cAn;
    done
}

#test1 '{print}'
test1 'BEGIN { ORS = "\0" } ; { print $0 }'
test1 '{ printf "%s\0", $0}'
test1 '{ printf( "%s%c", $0, 0 )}'

We get this results:

            awk      BEGIN { ORS = "\0" } ; { print $0 }   a  \0   b  \0   c  \0
           mawk      BEGIN { ORS = "\0" } ; { print $0 }   a   b   c
   original-awk      BEGIN { ORS = "\0" } ; { print $0 }   a   b   c
    busybox awk      BEGIN { ORS = "\0" } ; { print $0 }   a   b   c
            awk                     { printf "%s\0", $0}   a  \0   b  \0   c  \0
           mawk                     { printf "%s\0", $0}   a   b   c
   original-awk                     { printf "%s\0", $0}   a   b   c
    busybox awk                     { printf "%s\0", $0}   a   b   c
            awk               { printf( "%s%c", $0, 0 )}   a  \0   b  \0   c  \0
           mawk               { printf( "%s%c", $0, 0 )}   a  \0   b  \0   c  \0
   original-awk               { printf( "%s%c", $0, 0 )}   a  \0   b  \0   c  \0
    busybox awk               { printf( "%s%c", $0, 0 )}   a   b   c

As it can be seen above, the first two solutions work only in GNU AWK.

The most portable is the third solution: '{ printf( "%s%c", $0, 0 )}'.

No solution work correctly in "busybox awk".

The versions used for this tests were:

          awk> GNU Awk 4.0.1
         mawk> mawk 1.3.3 Nov 1996, Copyright (C) Michael D. Brennan
 original-awk> awk version 20110810
      busybox> BusyBox v1.20.2 (Debian 1:1.20.0-7) multi-call binary.