Shell pipe: Exit immediately when one command fails

Question

I\'m using a pipe of several commands in bash. Is there a way of configuring bash to terminate all commands in the whole pipeline immediately should one of the commands fail

Answer 1

The following code seems to work by Dash, but EXIT traps within pipe do not work in Bash; maybe it is a bug in Bash.

#!/bin/sh

echo PID of the shell: $$

trap 'echo In INT trap >&2; trap - EXIT INT; kill -s INT $$' INT

(
    # now in subshell
    pidofsubshell=$(exec sh -c 'echo "$PPID"')
    # $BASHPID can be used as a value, when using Bash
    echo PID of subshell: $pidofsubshell

    fifo=$(mktemp -u); shells=$(mktemp) childs=$(mktemp)
    mkfifo $fifo
    trap 'echo In sub trap >&2; rm $fifo $shells $childs; trap - EXIT; exit' EXIT HUP TERM INT ALRM

    pipe_trap() {
        code=$?
        echo In sub sub trap $1 >&2
        echo $1 $code >> $fifo
    }
    { trap 'echo In pipe signal trap >&2; kill $(cat $childs $shells) 2>/dev/null' INT HUP TERM ALRM
        { trap 'pipe_trap 1' EXIT
            sleep 30; } \
        | { trap 'pipe_trap 2' EXIT
            sleep 50 & sleep 2; } \
        | { trap 'pipe_trap 3' EXIT
            sleep 40; } &
    }

    echo ps tail:
    ps xao pid,ppid,pgid,sid,command | head -n 1
    ps xao pid,ppid,pgid,sid,command | tail -n 15
        ps -o pid= --ppid $pidofsubshell | head -n -2 > $shells # strip pids of ps and head
    echo shells:
    cat $shells
        while read -r ppid; do ps -o pid= --ppid $ppid; done <$shells >$childs
    echo childs of above
    cat $childs

    { 
        IFS=' ' read -r id exitcode
        echo Pipe part nr. $id terminated first with code $exitcode\; killing the remaining processes.
        kill $(cat $childs $shells) 2>/dev/null
    } < $fifo
)

echo
echo After subshell:
ps xao pid,ppid,pgid,sid,command | head -n 1
ps xao pid,ppid,pgid,sid,command | tail -n 15