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  • Bug#872956: [debian-policy] warn about danger of pipe in shell snippet

    From Bastien =?UTF-8?Q?ROUCARI=C3=88S?=@21:1/5 to All on Wed Aug 23 01:30:02 2017
    XPost: linux.debian.bugs.dist

    Package: debian-policy
    Version: 4.0.1.0
    Severity: normal

    set -e is not suffisant to detect error in pipe context

    cat nonexistant | sed s/some//g will hapilly return 0 and do not fail

    exec 3>&1; s=$(exec 4>&1 >&3; { cat nonexistant ; echo $? >&4; } | sed s/some//g ) && exit $s

    this could be simplified by using make function
    PIPESAFE=exec 3>&1; s=$$(exec 4>&1 >&3; { $(1) ; echo $$? >&4; } | $(2)) && exit $$s

    Could deserve a footnote on 4.6. Error trapping in makefiles




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  • From Jonathan Nieder@21:1/5 to All on Wed Aug 23 02:10:02 2017
    XPost: linux.debian.bugs.dist

    Hi,

    Bastien ROUCARIÈS wrote:

    set -e is not suffisant to detect error in pipe context

    cat nonexistant | sed s/some//g will hapilly return 0 and do not fail

    exec 3>&1; s=$(exec 4>&1 >&3; { cat nonexistant ; echo $? >&4; } | sed s/some//g ) && exit $s

    this could be simplified by using make function
    PIPESAFE=exec 3>&1; s=$$(exec 4>&1 >&3; { $(1) ; echo $$? >&4; } | $(2)) && exit $$s

    Could deserve a footnote on 4.6. Error trapping in makefiles

    I don't think this belongs in policy. Maybe devref?

    By the way, if you're using bash (https://www.gnu.org/software/make/manual/html_node/Choosing-the-Shell.html), you can use "set -o pipefail" to handle this kind of case.

    Thanks,
    Jonathan

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