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Errno - System errno constants


use Errno qw(EINTR EIO :POSIX);


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.


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;


Graham Barr <>


Copyright (c) 1997-8 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.