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Universal::Errno zef:Garlandg last updated on 2021-07-10



Universal::Errno - Errno wrapper for Linux, Unix, and Windows


use Universal::Errno;


  say errno;
  say "failed: {errno}";
  say +errno;              #2


Universal::Errno is an extension of and wrapper around lizmat´s Unix::errno, and exports the same errno and set_errno interface. It works on Linux, Windows, and Macos. BSD support is untested, but should work.

One added feature is the strerror method, which gets the string for the error in a thread-safe way. On platforms that support it, it uses POSIX strerror_l. This allows getting the error string that corresponds to the user´s set locale. On platforms that do not support it, strerror_r (XSI) is used. On Windows, this is done using GetLastError() and FormatMessageW. Windows also has a SetLastError function which is used instead of masking the value.

This module provides an Exception class, X::Errno. To check the type of error in a portable way, use the symbol method and smartmatch against an entry in the Errno enum.

It also provides a trait: error-model. Mark a sub or method with is error-model<errno> and the trait will automatically box the errno for you and reset errno to 0.

Important note: With a native sub, the is native trait must come before is error-model.

For calls that return -errno, there is also the trait is error-model<neg-errno>.

If high-performance is needed for a native sub that can return errno, use the check-errno and/or check-neg-errno subs. These subs are interchangeable with the traits, but cannot be directly applied to a nativecall subroutine.

As an example of a real-world scenario, this code sets up a socket using socket(2) and handles the errors with a CATCH block.

use NativeCall;
use Constants::Sys::Socket;
use Universal::Errno;

sub socket(int32, int32, int32) returns int32 is native is error-model<errno> { ... }
my int32 $socket;

try {
  $socket = socket(AF::INET, SOCK_DGRAM, 0);

  # Do something with $socket

    when X::Errno {
      given .symbol {
        when Errno::EINVAL {
          die "Invalid socket type"
        when Errno::EACCES {
          die "Permission denied"

class X::Errno

Base exception class for errno

method message

method message() returns Mu

Get the Str message for this errno value.

method symbol

method symbol() returns Mu

Get the symbol of this errno value.

method Int

method Int() returns Mu

Get the integer that corresponds to this errno value.

method Numeric

method Numeric() returns Mu

Get the numeric value of this errno value.

multi method new

multi method new() returns Mu

Get a new Errno exception from errno. This resets errno to 0.


multi sub trait_mod:

multi sub trait_mod:<is>(
    Routine $s,
    :$error-model where { ... }
) returns Mu

Trait to check return value of subroutine and throw X::Errno if return value is less than 1.

multi sub trait_mod:

multi sub trait_mod:<is>(
    Routine $s,
    :$error-model where { ... }
) returns Mu

Trait to check return value of subroutine and throw abs(return value) as X::Errno if return value is less than 1.

sub check-neg-errno

sub check-neg-errno(
    Int $result
) returns Mu

Check the result against the negative errno form.

sub check-errno

sub check-errno(
    Int $result
) returns Mu

Check the result against the errno() form.


Travis Gibson [email protected]


Uses a heavily-modified Unix::errno module for Unix-like OSes. The Windows version module borrows its structure and interface from lizmat's Unix::errno.

Universal::Errno::Unix contains all of the modified code, and this README also borrows the SYNOPSIS example above. The original README and COPYRIGHT information for lizmat's Unix::errno has been preserved in Universal::Errno::Unix.

lizmat's Unix::errno can be found at


Copyright 2021 Travis Gibson

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.