If you launch an external program via open() and a trailing pipe "|" character to read from its STDOUT, open() will only return a false value if it can't find the program specified: 
open PIPE, "pfrrzt |" or die "failed!";

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This will correctly print an error message and die() afterwards: 
Can't exec "pfrrzt": No such file or directory 
at ./test line 9.
failed! at ./t line 9.

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But if the command redirects its standard output to /dev/null, open will return a true value instead: 
open PIPE, "pfrrzt >/dev/null |" or die "failed!";

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which doesn't trigger the die() statement.

Interestingly, the popen() function used internally won't catch a non-existing program name and return an OK pointer to a FILE struct either way.

What's the magic at the Perl level that causes the behavior mentioned above? ~

In reply to Weird open() return code in pipe mode by saintmike

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