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local/lib/perl5/IO/Async/ChildManager.pm  view on Meta::CPAN

#  You may distribute under the terms of either the GNU General Public License
#  or the Artistic License (the same terms as Perl itself)
#
#  (C) Paul Evans, 2007-2014 -- leonerd@leonerd.org.uk

package IO::Async::ChildManager;

use strict;
use warnings;

our $VERSION = '0.70';

# Not a notifier

use IO::Async::Stream;

use IO::Async::OS;

use Carp;
use Scalar::Util qw( weaken );

use POSIX qw( _exit dup dup2 nice );

use constant LENGTH_OF_I => length( pack( "I", 0 ) );

=head1 NAME

C<IO::Async::ChildManager> - facilitates the execution of child processes

=head1 SYNOPSIS

This object is used indirectly via an L<IO::Async::Loop>:

 use IO::Async::Loop;

 my $loop = IO::Async::Loop->new;

 ...

 $loop->run_child(
    command => "/bin/ps",

    on_finish => sub {
       my ( $pid, $exitcode, $stdout, $stderr ) = @_;
       my $status = ( $exitcode >> 8 );
       print "ps [PID $pid] exited with status $status\n";
    },
 );

 $loop->open_child(
    command => [ "/bin/ping", "-c4", "some.host" ],

    stdout => {
       on_read => sub {
          my ( $stream, $buffref, $eof ) = @_;
          while( $$buffref =~ s/^(.*)\n// ) {
             print "PING wrote: $1\n";
          }
          return 0;
       },
    },

    on_finish => sub {
       my ( $pid, $exitcode ) = @_;
       my $status = ( $exitcode >> 8 );
       ...
    },
 );

 my ( $pipeRd, $pipeWr ) = IO::Async::OS->pipepair;
 $loop->spawn_child(
    command => "/usr/bin/my-command",

    setup => [
       stdin  => [ "open", "<", "/dev/null" ],
       stdout => $pipeWr,
       stderr => [ "open", ">>", "/var/log/mycmd.log" ],
       chdir  => "/",
    ]

    on_exit => sub {
       my ( $pid, $exitcode ) = @_;
       my $status = ( $exitcode >> 8 );
       print "Command exited with status $status\n";
    },
 );

 $loop->spawn_child(
    code => sub {
       do_something; # executes in a child process
       return 1;
    },

    on_exit => sub {
       my ( $pid, $exitcode, $dollarbang, $dollarat ) = @_;
       my $status = ( $exitcode >> 8 );
       print "Child process exited with status $status\n";
       print " OS error was $dollarbang, exception was $dollarat\n";
    },
 );

=head1 DESCRIPTION

This module extends the functionality of the containing L<IO::Async::Loop> to
manage the execution of child processes. It acts as a central point to store
PID values of currently-running children, and to call the appropriate
continuation handler code when the process terminates. It provides useful
wrapper methods that set up filehandles and other child process details, and
to capture the child process's STDOUT and STDERR streams.

=cut

# Writing to variables of $> and $) have tricky ways to obtain error results
sub setuid
{
   my ( $uid ) = @_;

   $> = $uid; my $saved_errno = $!;
   $> == $uid and return 1;

   $! = $saved_errno;
   return undef;
}

sub setgid
{
   my ( $gid ) = @_;

   $) = $gid; my $saved_errno = $!;
   $) == $gid and return 1;

   $! = $saved_errno;
   return undef;
}

sub setgroups
{

local/lib/perl5/IO/Async/ChildManager.pm  view on Meta::CPAN

   close( $writepipe );
   return $self->_spawn_in_parent( $readpipe, $kid, $on_exit );
}

=head2 C<setup> array

This array gives a list of file descriptor operations to perform in the child
process after it has been C<fork(2)>ed from the parent, before running the code
or command. It consists of name/value pairs which are ordered; the operations
are performed in the order given.

=over 8

=item fdI<n> => ARRAY

Gives an operation on file descriptor I<n>. The first element of the array
defines the operation to be performed:

=over 4

=item [ 'close' ]

The file descriptor will be closed.

=item [ 'dup', $io ]

The file descriptor will be C<dup2(2)>ed from the given IO handle.

=item [ 'open', $mode, $file ]

The file descriptor will be opened from the named file in the given mode. The
C<$mode> string should be in the form usually given to the C<open> function;
such as '<' or '>>'.

=item [ 'keep' ]

The file descriptor will not be closed; it will be left as-is.

=back

A non-reference value may be passed as a shortcut, where it would contain the
name of the operation with no arguments (i.e. for the C<close> and C<keep>
operations).

=item IO => ARRAY

Shortcut for passing C<fdI<n>>, where I<n> is the fileno of the IO
reference. In this case, the key must be a reference that implements the
C<fileno> method. This is mostly useful for

 $handle => 'keep'

=item fdI<n> => IO

A shortcut for the C<dup> case given above.

=item stdin => ...

=item stdout => ...

=item stderr => ...

Shortcuts for C<fd0>, C<fd1> and C<fd2> respectively.

=item env => HASH

A reference to a hash to set as the child process's environment.

Note that this will entirely set a new environment, completely replacing the
existing one. If you want to simply add new keys or change the values of some
keys without removing the other existing ones, you can simply copy C<%ENV>
into the hash before setting new keys:

 env => {
    %ENV,
    ANOTHER => "key here",
 }

=item nice => INT

Change the child process's scheduling priority using C<POSIX::nice>.

=item chdir => STRING

Change the child process's working directory using C<chdir>.

=item setuid => INT

=item setgid => INT

Change the child process's effective UID or GID.

=item setgroups => ARRAY

Change the child process's groups list, to those groups whose numbers are
given in the ARRAY reference.

On most systems, only the privileged superuser change user or group IDs.
L<IO::Async> will B<NOT> check before detaching the child process whether
this is the case.

If setting both the primary GID and the supplementary groups list, it is
suggested to set the primary GID first. Moreover, some operating systems may
require that the supplementary groups list contains the primary GID.

=back

If no directions for what to do with C<stdin>, C<stdout> and C<stderr> are
given, a default of C<keep> is implied. All other file descriptors will be
closed, unless a C<keep> operation is given for them.

If C<setuid> is used, be sure to place it after any other operations that
might require superuser privileges, such as C<setgid> or opening special
files.

=cut

sub _check_setup_and_canonicise
{
   my $self = shift;
   my ( $setup ) = @_;

   ref $setup eq "ARRAY" or croak "'setup' must be an ARRAY reference";

   return () if !@$setup;

   my @setup;

   my $has_setgroups;

   foreach my $i ( 0 .. $#$setup / 2 ) {
      my ( $key, $value ) = @$setup[$i*2, $i*2 + 1];

      # Rewrite stdin/stdout/stderr
      $key eq "stdin"  and $key = "fd0";
      $key eq "stdout" and $key = "fd1";
      $key eq "stderr" and $key = "fd2";

      # Rewrite other filehandles
      ref $key and eval { $key->fileno; 1 } and $key = "fd" . $key->fileno;

      if( $key =~ m/^fd(\d+)$/ ) {
         my $fd = $1;
         my $ref = ref $value;

         if( !$ref ) {
            $value = [ $value ];
         }
         elsif( $ref eq "ARRAY" ) {
            # Already OK
         }
         elsif( $ref eq "GLOB" or eval { $value->isa( "IO::Handle" ) } ) {
            $value = [ 'dup', $value ];
         }
         else {
            croak "Unrecognised reference type '$ref' for file descriptor $fd";
         }

         my $operation = $value->[0];
         grep { $_ eq $operation } qw( open close dup keep ) or 
            croak "Unrecognised operation '$operation' for file descriptor $fd";
      }
      elsif( $key eq "env" ) {
         ref $value eq "HASH" or croak "Expected HASH reference for 'env' setup key";
      }
      elsif( $key eq "nice" ) {
         $value =~ m/^\d+$/ or croak "Expected integer for 'nice' setup key";
      }
      elsif( $key eq "chdir" ) {
         # This isn't a purely watertight test, but it does guard against
         # silly things like passing a reference - directories such as
         # ARRAY(0x12345) are unlikely to exist
         -d $value or croak "Working directory '$value' does not exist";
      }
      elsif( $key eq "setuid" ) {
         $value =~ m/^\d+$/ or croak "Expected integer for 'setuid' setup key";
      }
      elsif( $key eq "setgid" ) {
         $value =~ m/^\d+$/ or croak "Expected integer for 'setgid' setup key";
         $has_setgroups and carp "It is suggested to 'setgid' before 'setgroups'";
      }
      elsif( $key eq "setgroups" ) {
         ref $value eq "ARRAY" or croak "Expected ARRAY reference for 'setgroups' setup key";
         m/^\d+$/ or croak "Expected integer in 'setgroups' array" for @$value;
         $has_setgroups = 1;
      }
      else {
         croak "Unrecognised setup operation '$key'";
      }

      push @setup, $key => $value;
   }

   return @setup;
}

sub _spawn_in_parent