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t/lib/Capture/Tiny.pm view on Meta::CPAN

use strict;
use warnings;
package Capture::Tiny;
# ABSTRACT: Capture STDOUT and STDERR from Perl, XS or external programs
our $VERSION = '0.23'; # VERSION
use Carp ();
use Exporter ();
use IO::Handle ();
use File::Spec ();
use File::Temp qw/tempfile tmpnam/;
use Scalar::Util qw/reftype blessed/;
# Get PerlIO or fake it
BEGIN {
  local $@;
  eval { require PerlIO; PerlIO->can('get_layers') }
    or *PerlIO::get_layers = sub { return () };
}

#--------------------------------------------------------------------------#
# create API subroutines and export them
# [do STDOUT flag, do STDERR flag, do merge flag, do tee flag]
#--------------------------------------------------------------------------#

my %api = (
  capture         => [1,1,0,0],
  capture_stdout  => [1,0,0,0],
  capture_stderr  => [0,1,0,0],
  capture_merged  => [1,1,1,0],
  tee             => [1,1,0,1],
  tee_stdout      => [1,0,0,1],
  tee_stderr      => [0,1,0,1],
  tee_merged      => [1,1,1,1],
);

for my $sub ( keys %api ) {
  my $args = join q{, }, @{$api{$sub}};
  eval "sub $sub(&;@) {unshift \@_, $args; goto \\&_capture_tee;}"; ## no critic
}

our @ISA = qw/Exporter/;
our @EXPORT_OK = keys %api;
our %EXPORT_TAGS = ( 'all' => \@EXPORT_OK );

#--------------------------------------------------------------------------#
# constants and fixtures
#--------------------------------------------------------------------------#

my $IS_WIN32 = $^O eq 'MSWin32';

##our $DEBUG = $ENV{PERL_CAPTURE_TINY_DEBUG};
##
##my $DEBUGFH;
##open $DEBUGFH, "> DEBUG" if $DEBUG;
##
##*_debug = $DEBUG ? sub(@) { print {$DEBUGFH} @_ } : sub(){0};

our $TIMEOUT = 30;

#--------------------------------------------------------------------------#
# command to tee output -- the argument is a filename that must
# be opened to signal that the process is ready to receive input.
# This is annoying, but seems to be the best that can be done
# as a simple, portable IPC technique
#--------------------------------------------------------------------------#
my @cmd = ($^X, '-C0', '-e', '$SIG{HUP}=sub{exit}; '
  . 'if( my $fn=shift ){ open my $fh, qq{>$fn}; print {$fh} $$; close $fh;} '
  . 'my $buf; while (sysread(STDIN, $buf, 2048)) { '
  . 'syswrite(STDOUT, $buf); syswrite(STDERR, $buf)}'
);

#--------------------------------------------------------------------------#
# filehandle manipulation
#--------------------------------------------------------------------------#

sub _relayer {
  my ($fh, $layers) = @_;
  # _debug("# requested layers (@{$layers}) for @{[fileno $fh]}\n");
  my %seen = ( unix => 1, perlio => 1 ); # filter these out
  my @unique = grep { !$seen{$_}++ } @$layers;
  # _debug("# applying unique layers (@unique) to @{[fileno $fh]}\n");
  binmode($fh, join(":", ":raw", @unique));
}

sub _name {
  my $glob = shift;
  no strict 'refs'; ## no critic
  return *{$glob}{NAME};
}

sub _open {
  open $_[0], $_[1] or Carp::confess "Error from open(" . join(q{, }, @_) . "): $!";
  # _debug( "# open " . join( ", " , map { defined $_ ? _name($_) : 'undef' } @_ ) . " as " . fileno( $_[0] ) . "\n" );
}

sub _close {
  # _debug( "# closing " . ( defined $_[0] ? _name($_[0]) : 'undef' )  . " on " . fileno( $_[0] ) . "\n" );
  close $_[0] or Carp::confess "Error from close(" . join(q{, }, @_) . "): $!";
}

my %dup; # cache this so STDIN stays fd0
my %proxy_count;
sub _proxy_std {
  my %proxies;
  if ( ! defined fileno STDIN ) {
    $proxy_count{stdin}++;
    if (defined $dup{stdin}) {
      _open \*STDIN, "<&=" . fileno($dup{stdin});
      # _debug( "# restored proxy STDIN as " . (defined fileno STDIN ? fileno STDIN : 'undef' ) . "\n" );
    }
    else {
      _open \*STDIN, "<" . File::Spec->devnull;
      # _debug( "# proxied STDIN as " . (defined fileno STDIN ? fileno STDIN : 'undef' ) . "\n" );
      _open $dup{stdin} = IO::Handle->new, "<&=STDIN";
    }
    $proxies{stdin} = \*STDIN;
    binmode(STDIN, ':utf8') if $] >= 5.008; ## no critic
  }
  if ( ! defined fileno STDOUT ) {
    $proxy_count{stdout}++;
    if (defined $dup{stdout}) {
      _open \*STDOUT, ">&=" . fileno($dup{stdout});

t/lib/Capture/Tiny.pm view on Meta::CPAN

    }
    $proxies{stderr} = \*STDERR;
    binmode(STDERR, ':utf8') if $] >= 5.008; ## no critic
  }
  return %proxies;
}

sub _unproxy {
  my (%proxies) = @_;
  # _debug( "# unproxying: " . join(" ", keys %proxies) . "\n" );
  for my $p ( keys %proxies ) {
    $proxy_count{$p}--;
    # _debug( "# unproxied " . uc($p) . " ($proxy_count{$p} left)\n" );
    if ( ! $proxy_count{$p} ) {
      _close $proxies{$p};
      _close $dup{$p} unless $] < 5.008; # 5.6 will have already closed this as dup
      delete $dup{$p};
    }
  }
}

sub _copy_std {
  my %handles;
  for my $h ( qw/stdout stderr stdin/ ) {
    next if $h eq 'stdin' && ! $IS_WIN32; # WIN32 hangs on tee without STDIN copied
    my $redir = $h eq 'stdin' ? "<&" : ">&";
    _open $handles{$h} = IO::Handle->new(), $redir . uc($h); # ">&STDOUT" or "<&STDIN"
  }
  return \%handles;
}

# In some cases we open all (prior to forking) and in others we only open
# the output handles (setting up redirection)
sub _open_std {
  my ($handles) = @_;
  _open \*STDIN, "<&" . fileno $handles->{stdin} if defined $handles->{stdin};
  _open \*STDOUT, ">&" . fileno $handles->{stdout} if defined $handles->{stdout};
  _open \*STDERR, ">&" . fileno $handles->{stderr} if defined $handles->{stderr};
}

#--------------------------------------------------------------------------#
# private subs
#--------------------------------------------------------------------------#

sub _start_tee {
  my ($which, $stash) = @_; # $which is "stdout" or "stderr"
  # setup pipes
  $stash->{$_}{$which} = IO::Handle->new for qw/tee reader/;
  pipe $stash->{reader}{$which}, $stash->{tee}{$which};
  # _debug( "# pipe for $which\: " .  _name($stash->{tee}{$which}) . " " . fileno( $stash->{tee}{$which} ) . " => " . _name($stash->{reader}{$which}) . " " . fileno( $stash->{reader}{$which}) . "\n" );
  select((select($stash->{tee}{$which}), $|=1)[0]); # autoflush
  # setup desired redirection for parent and child
  $stash->{new}{$which} = $stash->{tee}{$which};
  $stash->{child}{$which} = {
    stdin   => $stash->{reader}{$which},
    stdout  => $stash->{old}{$which},
    stderr  => $stash->{capture}{$which},
  };
  # flag file is used to signal the child is ready
  $stash->{flag_files}{$which} = scalar tmpnam();
  # execute @cmd as a separate process
  if ( $IS_WIN32 ) {
    local $@;
    eval "use Win32API::File qw/CloseHandle GetOsFHandle SetHandleInformation fileLastError HANDLE_FLAG_INHERIT INVALID_HANDLE_VALUE/ ";
    # _debug( "# Win32API::File loaded\n") unless $@;
    my $os_fhandle = GetOsFHandle( $stash->{tee}{$which} );
    # _debug( "# Couldn't get OS handle: " . fileLastError() . "\n") if ! defined $os_fhandle || $os_fhandle == INVALID_HANDLE_VALUE();
    my $result = SetHandleInformation( $os_fhandle, HANDLE_FLAG_INHERIT(), 0);
    # _debug( $result ? "# set no-inherit flag on $which tee\n" : ("# can't disable tee handle flag inherit: " . fileLastError() . "\n"));
    _open_std( $stash->{child}{$which} );
    $stash->{pid}{$which} = system(1, @cmd, $stash->{flag_files}{$which});
    # not restoring std here as it all gets redirected again shortly anyway
  }
  else { # use fork
    _fork_exec( $which, $stash );
  }
}

sub _fork_exec {
  my ($which, $stash) = @_; # $which is "stdout" or "stderr"
  my $pid = fork;
  if ( not defined $pid ) {
    Carp::confess "Couldn't fork(): $!";
  }
  elsif ($pid == 0) { # child
    # _debug( "# in child process ...\n" );
    untie *STDIN; untie *STDOUT; untie *STDERR;
    _close $stash->{tee}{$which};
    # _debug( "# redirecting handles in child ...\n" );
    _open_std( $stash->{child}{$which} );
    # _debug( "# calling exec on command ...\n" );
    exec @cmd, $stash->{flag_files}{$which};
  }
  $stash->{pid}{$which} = $pid
}

my $have_usleep = eval "use Time::HiRes 'usleep'; 1";
sub _files_exist {
  return 1 if @_ == grep { -f } @_;
  Time::HiRes::usleep(1000) if $have_usleep;
  return 0;
}

sub _wait_for_tees {
  my ($stash) = @_;
  my $start = time;
  my @files = values %{$stash->{flag_files}};
  my $timeout = defined $ENV{PERL_CAPTURE_TINY_TIMEOUT}
              ? $ENV{PERL_CAPTURE_TINY_TIMEOUT} : $TIMEOUT;
  1 until _files_exist(@files) || ($timeout && (time - $start > $timeout));
  Carp::confess "Timed out waiting for subprocesses to start" if ! _files_exist(@files);
  unlink $_ for @files;
}

sub _kill_tees {
  my ($stash) = @_;
  if ( $IS_WIN32 ) {
    # _debug( "# closing handles with CloseHandle\n");
    CloseHandle( GetOsFHandle($_) ) for values %{ $stash->{tee} };
    # _debug( "# waiting for subprocesses to finish\n");
    my $start = time;
    1 until wait == -1 || (time - $start > 30);
  }
  else {
    _close $_ for values %{ $stash->{tee} };
    waitpid $_, 0 for values %{ $stash->{pid} };
  }
}

sub _slurp {
  my ($name, $stash) = @_;
  my ($fh, $pos) = map { $stash->{$_}{$name} } qw/capture pos/;
  # _debug( "# slurping captured $name from " . fileno($fh) . " at pos $pos with layers: @{[PerlIO::get_layers($fh)]}\n");
  seek( $fh, $pos, 0 ) or die "Couldn't seek on capture handle for $name\n";
  my $text = do { local $/; scalar readline $fh };
  return defined($text) ? $text : "";
}

#--------------------------------------------------------------------------#
# _capture_tee() -- generic main sub for capturing or teeing
#--------------------------------------------------------------------------#

sub _capture_tee {
  # _debug( "# starting _capture_tee with (@_)...\n" );
  my ($do_stdout, $do_stderr, $do_merge, $do_tee, $code, @opts) = @_;
  my %do = ($do_stdout ? (stdout => 1) : (),  $do_stderr ? (stderr => 1) : ());
  Carp::confess("Custom capture options must be given as key/value pairs\n")
    unless @opts % 2 == 0;
  my $stash = { capture => { @opts } };
  for ( keys %{$stash->{capture}} ) {
    my $fh = $stash->{capture}{$_};
    Carp::confess "Custom handle for $_ must be seekable\n"
      unless ref($fh) eq 'GLOB' || (blessed($fh) && $fh->isa("IO::Seekable"));
  }
  # save existing filehandles and setup captures
  local *CT_ORIG_STDIN  = *STDIN ;
  local *CT_ORIG_STDOUT = *STDOUT;
  local *CT_ORIG_STDERR = *STDERR;
  # find initial layers
  my %layers = (
    stdin   => [PerlIO::get_layers(\*STDIN) ],
    stdout  => [PerlIO::get_layers(\*STDOUT, output => 1)],
    stderr  => [PerlIO::get_layers(\*STDERR, output => 1)],
  );
  # _debug( "# existing layers for $_\: @{$layers{$_}}\n" ) for qw/stdin stdout stderr/;
  # get layers from underlying glob of tied filehandles if we can
  # (this only works for things that work like Tie::StdHandle)
  $layers{stdout} = [PerlIO::get_layers(tied *STDOUT)]
    if tied(*STDOUT) && (reftype tied *STDOUT eq 'GLOB');
  $layers{stderr} = [PerlIO::get_layers(tied *STDERR)]
    if tied(*STDERR) && (reftype tied *STDERR eq 'GLOB');
  # _debug( "# tied object corrected layers for $_\: @{$layers{$_}}\n" ) for qw/stdin stdout stderr/;
  # bypass scalar filehandles and tied handles
  # localize scalar STDIN to get a proxy to pick up FD0, then restore later to CT_ORIG_STDIN
  my %localize;
  $localize{stdin}++,  local(*STDIN)
    if grep { $_ eq 'scalar' } @{$layers{stdin}};
  $localize{stdout}++, local(*STDOUT)
    if $do_stdout && grep { $_ eq 'scalar' } @{$layers{stdout}};
  $localize{stderr}++, local(*STDERR)
    if ($do_stderr || $do_merge) && grep { $_ eq 'scalar' } @{$layers{stderr}};
  $localize{stdin}++, local(*STDIN), _open( \*STDIN, "<&=0")
    if tied *STDIN && $] >= 5.008;
  $localize{stdout}++, local(*STDOUT), _open( \*STDOUT, ">&=1")
    if $do_stdout && tied *STDOUT && $] >= 5.008;
  $localize{stderr}++, local(*STDERR), _open( \*STDERR, ">&=2")
    if ($do_stderr || $do_merge) && tied *STDERR && $] >= 5.008;
  # _debug( "# localized $_\n" ) for keys %localize;
  # proxy any closed/localized handles so we don't use fds 0, 1 or 2
  my %proxy_std = _proxy_std();
  # _debug( "# proxy std: @{ [%proxy_std] }\n" );
  # update layers after any proxying
  $layers{stdout} = [PerlIO::get_layers(\*STDOUT, output => 1)] if $proxy_std{stdout};
  $layers{stderr} = [PerlIO::get_layers(\*STDERR, output => 1)] if $proxy_std{stderr};
  # _debug( "# post-proxy layers for $_\: @{$layers{$_}}\n" ) for qw/stdin stdout stderr/;
  # store old handles and setup handles for capture
  $stash->{old} = _copy_std();
  $stash->{new} = { %{$stash->{old}} }; # default to originals
  for ( keys %do ) {
    $stash->{new}{$_} = ($stash->{capture}{$_} ||= File::Temp->new);
    seek( $stash->{capture}{$_}, 0, 2 ) or die "Could not seek on capture handle for $_\n";
    $stash->{pos}{$_} = tell $stash->{capture}{$_};
    # _debug("# will capture $_ on " . fileno($stash->{capture}{$_})."\n" );
    _start_tee( $_ => $stash ) if $do_tee; # tees may change $stash->{new}
  }
  _wait_for_tees( $stash ) if $do_tee;
  # finalize redirection
  $stash->{new}{stderr} = $stash->{new}{stdout} if $do_merge;
  # _debug( "# redirecting in parent ...\n" );
  _open_std( $stash->{new} );
  # execute user provided code
  my ($exit_code, $inner_error, $outer_error, @result);
  {
    local *STDIN = *CT_ORIG_STDIN if $localize{stdin}; # get original, not proxy STDIN
    # _debug( "# finalizing layers ...\n" );
    _relayer(\*STDOUT, $layers{stdout}) if $do_stdout;
    _relayer(\*STDERR, $layers{stderr}) if $do_stderr;
    # _debug( "# running code $code ...\n" );
    local $@;
    eval { @result = $code->(); $inner_error = $@ };
    $exit_code = $?; # save this for later
    $outer_error = $@; # save this for later
  }
  # restore prior filehandles and shut down tees
  # _debug( "# restoring filehandles ...\n" );
  _open_std( $stash->{old} );
  _close( $_ ) for values %{$stash->{old}}; # don't leak fds
  # shouldn't need relayering originals, but see rt.perl.org #114404
  _relayer(\*STDOUT, $layers{stdout}) if $do_stdout;
  _relayer(\*STDERR, $layers{stderr}) if $do_stderr;
  _unproxy( %proxy_std );
  # _debug( "# killing tee subprocesses ...\n" ) if $do_tee;
  _kill_tees( $stash ) if $do_tee;
  # return captured output, but shortcut in void context
  # unless we have to echo output to tied/scalar handles;
  my %got;
  if ( defined wantarray or ($do_tee && keys %localize) ) {
    for ( keys %do ) {
      _relayer($stash->{capture}{$_}, $layers{$_});
      $got{$_} = _slurp($_, $stash);
      # _debug("# slurped " . length($got{$_}) . " bytes from $_\n");
    }
    print CT_ORIG_STDOUT $got{stdout}
      if $do_stdout && $do_tee && $localize{stdout};
    print CT_ORIG_STDERR $got{stderr}
      if $do_stderr && $do_tee && $localize{stderr};
  }
  $? = $exit_code;
  $@ = $inner_error if $inner_error;
  die $outer_error if $outer_error;
  # _debug( "# ending _capture_tee with (@_)...\n" );
  return unless defined wantarray;
  my @return;
  push @return, $got{stdout} if $do_stdout;
  push @return, $got{stderr} if $do_stderr && ! $do_merge;
  push @return, @result;
  return wantarray ? @return : $return[0];
}

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Capture::Tiny - Capture STDOUT and STDERR from Perl, XS or external programs

=head1 VERSION

version 0.23

=head1 SYNOPSIS

   use Capture::Tiny ':all';
 
   # capture from external command
 
   ($stdout, $stderr, $exit) = capture {
     system( $cmd, @args );
   };
 
   # capture from arbitrary code (Perl or external)
 
   ($stdout, $stderr, @result) = capture {
     # your code here
   };
 
   # capture partial or merged output

t/lib/Capture/Tiny.pm view on Meta::CPAN

Caution: STDOUT and STDERR output in the merged result are not guaranteed to be
properly ordered due to buffering.

=head1 LIMITATIONS

=head2 Portability

Portability is a goal, not a guarantee.  C<<< tee >>> requires fork, except on
Windows where C<<< system(1, @cmd) >>> is used instead.  Not tested on any
particularly esoteric platforms yet.  See the
L<CPAN Testers Matrix|http://matrix.cpantesters.org/?dist=Capture-Tiny>
for test result by platform.

=head2 PerlIO layers

Capture::Tiny does it's best to preserve PerlIO layers such as ':utf8' or
':crlf' when capturing (only for Perl 5.8.1+) .  Layers should be applied to
STDOUT or STDERR I<before> the call to C<<< capture >>> or C<<< tee >>>.  This may not work
for tied filehandles (see below).

=head2 Modifying filehandles before capturing

Generally speaking, you should do little or no manipulation of the standard IO
filehandles prior to using Capture::Tiny.  In particular, closing, reopening,
localizing or tying standard filehandles prior to capture may cause a variety of
unexpected, undesirable andE<sol>or unreliable behaviors, as described below.
Capture::Tiny does its best to compensate for these situations, but the
results may not be what you desire.

B<Closed filehandles>

Capture::Tiny will work even if STDIN, STDOUT or STDERR have been previously
closed.  However, since they will be reopened to capture or tee output, any
code within the captured block that depends on finding them closed will, of
course, not find them to be closed.  If they started closed, Capture::Tiny will
close them again when the capture block finishes.

Note that this reopening will happen even for STDIN or a filehandle not being
captured to ensure that the filehandle used for capture is not opened to file
descriptor 0, as this causes problems on various platforms.

Prior to Perl 5.12, closed STDIN combined with PERL_UNICODE=D leaks filehandles
and also breaks tee() for undiagnosed reasons.  So don't do that.

B<Localized filehandles>

If code localizes any of Perl's standard filehandles before capturing, the capture
will affect the localized filehandles and not the original ones.  External system
calls are not affected by localizing a filehandle in Perl and will continue
to send output to the original filehandles (which will thus not be captured).

B<Scalar filehandles>

If STDOUT or STDERR are reopened to scalar filehandles prior to the call to
C<<< capture >>> or C<<< tee >>>, then Capture::Tiny will override the output filehandle for
the duration of the C<<< capture >>> or C<<< tee >>> call and then, for C<<< tee >>>, send captured
output to the output filehandle after the capture is complete.  (Requires Perl
5.8)

Capture::Tiny attempts to preserve the semantics of STDIN opened to a scalar
reference, but note that external processes will not be able to read from such
a handle.  Capture::Tiny tries to ensure that external processes will read from
the null device instead, but this is not guaranteed.

B<Tied output filehandles>

If STDOUT or STDERR are tied prior to the call to C<<< capture >>> or C<<< tee >>>, then
Capture::Tiny will attempt to override the tie for the duration of the
C<<< capture >>> or C<<< tee >>> call and then send captured output to the tied filehandle after
the capture is complete.  (Requires Perl 5.8)

Capture::Tiny may not succeed resending UTF-8 encoded data to a tied
STDOUT or STDERR filehandle.  Characters may appear as bytes.  If the tied filehandle
is based on L<Tie::StdHandle>, then Capture::Tiny will attempt to determine
appropriate layers like C<<< :utf8 >>> from the underlying filehandle and do the right
thing.

B<Tied input filehandle>

Capture::Tiny attempts to preserve the semantics of tied STDIN, but this
requires Perl 5.8 and is not entirely predictable.  External processes
will not be able to read from such a handle.

Unless having STDIN tied is crucial, it may be safest to localize STDIN when
capturing:

   my ($out, $err) = do { local *STDIN; capture { ... } };

=head2 Modifying filehandles during a capture

Attempting to modify STDIN, STDOUT or STDERR I<during> C<<< capture >>> or C<<< tee >>> is
almost certainly going to cause problems.  Don't do that.

=head2 No support for Perl 5.8.0

It's just too buggy when it comes to layers and UTF-8.  Perl 5.8.1 or later
is recommended.

=head2 Limited support for Perl 5.6

Perl 5.6 predates PerlIO.  UTF-8 data may not be captured correctly.

=head1 ENVIRONMENT

=head2 PERL_CAPTURE_TINY_TIMEOUT

Capture::Tiny uses subprocesses for C<<< tee >>>.  By default, Capture::Tiny will
timeout with an error if the subprocesses are not ready to receive data within
30 seconds (or whatever is the value of C<<< $Capture::Tiny::TIMEOUT >>>).  An
alternate timeout may be specified by setting the C<<< PERL_CAPTURE_TINY_TIMEOUT >>>
environment variable.  Setting it to zero will disable timeouts.

=head1 SEE ALSO

This module was, inspired by L<IO::CaptureOutput>, which provides
similar functionality without the ability to tee output and with more
complicated code and API.  L<IO::CaptureOutput> does not handle layers
or most of the unusual cases described in the L</Limitations> section and
I no longer recommend it.

There are many other CPAN modules that provide some sort of output capture,
albeit with various limitations that make them appropriate only in particular
circumstances.  I'm probably missing some.  The long list is provided to show
why I felt Capture::Tiny was necessary.

=over

=item *

L<IO::Capture>

=item *

L<IO::Capture::Extended>

=item *

L<IO::CaptureOutput>

=item *

L<IPC::Capture>

=item *

L<IPC::Cmd>

=item *

L<IPC::Open2>

=item *

L<IPC::Open3>

=item *

L<IPC::Open3::Simple>

=item *

L<IPC::Open3::Utils>

=item *

L<IPC::Run>

=item *

( run in 2.174 seconds using v1.01-cache-2.11-cpan-600a1bdf6e4 )