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


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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
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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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