# Errno - phpMan

## 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.

    On Windows, "Errno" also defines and conditionally exports all the
    Winsock error constants defined in your system WinError.h include file.
    These are included in a second export tag, ":WINSOCK".

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

        my $fh;
        unless (open($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.

    Perl automatically loads "Errno" the first time you use "%!", so you
    don't need an explicit "use".

## 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];
        }

## AUTHOR
    Graham Barr <<gbarr@pobox.com>>

## COPYRIGHT
    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.