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Posted by PerlFAQ Server on April 6, 2008, 9:03 pm
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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 .
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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.
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