P
PerlFAQ Server
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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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
perlfaq.pod.
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
perlfaq.pod.