Errno - System errno constants

- NAME
- SYNOPSIS
- DESCRIPTION
- CAVEATS
- AUTHOR
- COPYRIGHT

# 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.

Errno - System errno constants