-o pipefail makes while read loop ugly

[Thorsten Glaser]

tc.sh:

    set -x
    set -e
    cat >tc.in <<\EOF
    one eins
    two zwei
    three drei
    EOF

    while IFS=' ' read a b; do
            # $a = t* and it works
            [[ $a = o* ]] && echo $b
    done <tc.in | sort -u >tc.out

    echo after the loop
    cat tc.out
    echo and out

This works with t* both with set ±o pipefail, and with t* in ksh93, but t* in mksh with set -o pipefail makes it error out *after* the “while” because the last comparison error’d out.

Workarounds include negating the comparison…

            [[ $a != o* ]] || echo $b

… so that the loop always has $?=0, or:

    while :; do
            IFS=' ' read a b || break

Interestingly enough, removing the “| sort -u” also makes it work.

[Thorsten Glaser (mirabilos)]

This is, unfortunately, by design.

I’ve committed a manpage change (in CAVEATS) with a rationale, though.