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.\" ========================================================================
.\"
.IX Title "Time::Out 3pm"
.TH Time::Out 3pm "2023-11-30" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Time::Out \- Easily timeout long running operations
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Time::Out qw( timeout );
\&
\&  timeout $timeout => sub {
\&    # your operation is implemented here and will be interrupted
\&    # if it runs for more than $timeout seconds
\&  };
\&  if ( $@ ) {
\&    # operation timed\-out
\&  }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`Time::Out\*(C'\fR module provides an easy interface to \fBalarm\fR\|(2) based timeouts.
Nested timeouts are supported. The module exports the \f(CW\*(C`timeout()\*(C'\fR function by
default. The function returns whatever the code placed inside the subroutine
reference returns:
.PP
.Vb 1
\&  use Time::Out qw( timeout );
\&
\&  my $result = timeout 5 => sub {
\&    return 7;
\&  };
\&  # $result == 7
.Ve
.PP
If \f(CW\*(C`Time::Out\*(C'\fR sees that Time::HiRes has been loaded, it will use that
\&\f(CW\*(C`alarm()\*(C'\fR function (if available) instead of the default one, allowing float
timeout values to be used effectively:
.PP
.Vb 2
\&  use Time::HiRes qw();
\&  use Time::Out   qw( timeout );
\&
\&  timeout 3.1416 => sub {
\&    # ...
\&  };
.Ve
.SH "CAVEATS"
.IX Header "CAVEATS"
.IP "Blocking I/O on MSWin32" 2
.IX Item "Blocking I/O on MSWin32"
\&\fBalarm\fR\|(2) doesn't interrupt blocking I/O on MSWin32, so \f(CW\*(C`timeout()\*(C'\fR won't do
that either.
.ie n .IP "@_" 2
.el .IP "\f(CW@_\fR" 2
.IX Item "@_"
One drawback to using \f(CW\*(C`timeout()\*(C'\fR is that it masks \f(CW@_\fR in the affected
code.  This happens because the affected code is actually wrapped inside
another subroutine that provides it's own \f(CW@_\fR. You can get around this by
specifically passing your \f(CW@_\fR (or whatever you want for that matter) to
\&\f(CW\*(C`timeout()\*(C'\fR as such:
.Sp
.Vb 1
\&  use Time::Out qw( timeout );
\&
\&  sub foo {
\&    timeout 5, @_ => sub {
\&      @_;
\&    };
\&  }
\&  my @result = foo( 42, "Hello, World!" );
\&  # @result == ( 42, "Hello, World!" );
.Ve
.IP "Eval inside timeout" 2
.IX Item "Eval inside timeout"
If the affected code has its own exception handling using Try::Tiny for
example, the catch block has to be amended in a way so that it will rethrow an
exception, if it refers to a timeout:
.Sp
.Vb 3
\&  use Scalar::Util qw( blessed  );
\&  use Time::Out    qw( timeout );
\&  use Try::Tiny    qw( catch try );
\&
\&  timeout 5, sub {
\&    try {
\&      select( undef, undef, undef, 7 );
\&      die "bad\en";
\&    } catch {
\&      # rethrow exception, if it refers to a timeout
\&      die $_ if blessed $_ && $_\->isa( \*(AqTime::Out::Exception\*(Aq );
\&      # handle all other exceptions
\&    }
\&  };
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBalarm\fR\|(2), Sys::AlarmCall
.SH "AUTHORS"
.IX Header "AUTHORS"
Sven Willenbuecher, <sven.willenbuecher@gmx.de>
.PP
Patrick LeBoutillier, <patl@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2005\-2008 Patrick LeBoutillier, 2023 by Sven
Willenbuecher.
.PP
This is free software; you can redistribute it and/or modify it under the same
terms as the Perl 5 programming language system itself.