FAQ 8.26 Why doesn't open() return an error when a pipe open fails?

Discussion in 'Perl Misc' started by PerlFAQ Server, Apr 28, 2011.

  1. This is an excerpt from the latest version perlfaq8.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .

    --------------------------------------------------------------------

    8.26: Why doesn't open() return an error when a pipe open fails?

    If the second argument to a piped "open()" contains shell
    metacharacters, perl "fork()"s, then "exec()"s a shell to decode the
    metacharacters and eventually run the desired program. If the program
    couldn't be run, it's the shell that gets the message, not Perl. All
    your Perl program can find out is whether the shell itself could be
    successfully started. You can still capture the shell's STDERR and check
    it for error messages. See "How can I capture STDERR from an external
    command?" elsewhere in this document, or use the "IPC::Open3" module.

    If there are no shell metacharacters in the argument of "open()", Perl
    runs the command directly, without using the shell, and can correctly
    report whether the command started.



    --------------------------------------------------------------------

    The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
    are not necessarily experts in every domain where Perl might show up,
    so please include as much information as possible and relevant in any
    corrections. The perlfaq-workers also don't have access to every
    operating system or platform, so please include relevant details for
    corrections to examples that do not work on particular platforms.
    Working code is greatly appreciated.

    If you'd like to help maintain the perlfaq, see the details in
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    PerlFAQ Server, Apr 28, 2011
    #1
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