Errno

Section: Perl Programmers Reference Guide (3pm)
Updated: 2010-10-12
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NAME

Errno - System errno constants

SYNOPSIS

    use Errno qw(EINTR EIO :POSIX);

DESCRIPTION

"Errno" defines and conditionally exports all the error constants defined in your system "errno.h" include file. It has a single export tag, ":POSIX", which will export all POSIX defined error numbers.

"Errno" also makes "%!" magic such that each element of "%!" has a non-zero value only if $! is set to that value. For example:

    use Errno;

    unless (open(FH, "/fangorn/spouse")) {
        if ($!{ENOENT}) {
            warn "Get a wife!\n";
        } else {
            warn "This path is barred: $!";
        } 
    }

If a specified constant "EFOO" does not exist on the system, $!{EFOO} returns "". You may use "exists $!{EFOO}" to check whether the constant is available on the system.

CAVEATS

Importing a particular constant may not be very portable, because the import will fail on platforms that do not have that constant. A more portable way to set $! to a valid value is to use:

    if (exists &Errno::EFOO) {
        $! = &Errno::EFOO;
    }

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