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inc/inc_IPC-Cmd/IPC/Cmd.pm  view on Meta::CPAN

Utility function that tells you if C<IPC::Open3> is available.
If the verbose flag is passed, it will print diagnostic messages
if C<IPC::Open3> can not be found or loaded.

=cut


sub can_use_ipc_open3   {
    my $self    = shift;
    my $verbose = shift || 0;

    ### IPC::Open3 is not working on VMS because of a lack of fork.
    return if IS_VMS;

    ### IPC::Open3 works on every non-VMS platform platform, but it can't
    ### capture buffers on win32 :(
    return unless can_load(
        modules => { map {$_ => '0.0'} qw|IPC::Open3 IO::Select Symbol| },
        verbose => ($WARN && $verbose),
    );

    return $IPC::Open3::VERSION;
}

=head2 $bool = IPC::Cmd->can_capture_buffer

Utility function that tells you if C<IPC::Cmd> is capable of
capturing buffers in it's current configuration.

=cut

sub can_capture_buffer {
    my $self    = shift;

    return 1 if $USE_IPC_RUN    && $self->can_use_ipc_run;
    return 1 if $USE_IPC_OPEN3  && $self->can_use_ipc_open3;
    return;
}

=head2 $bool = IPC::Cmd->can_use_run_forked

Utility function that tells you if C<IPC::Cmd> is capable of
providing C<run_forked> on the current platform.

=head1 FUNCTIONS

=head2 $path = can_run( PROGRAM );

C<can_run> takes only one argument: the name of a binary you wish
to locate. C<can_run> works much like the unix binary C<which> or the bash
command C<type>, which scans through your path, looking for the requested
binary.

Unlike C<which> and C<type>, this function is platform independent and
will also work on, for example, Win32.

If called in a scalar context it will return the full path to the binary
you asked for if it was found, or C<undef> if it was not.

If called in a list context and the global variable C<$INSTANCES> is a true
value, it will return a list of the full paths to instances
of the binary where found in C<PATH>, or an empty list if it was not found.

=cut

sub can_run {
    my $command = shift;

    # a lot of VMS executables have a symbol defined
    # check those first
    if ( $^O eq 'VMS' ) {
        require VMS::DCLsym;
        my $syms = VMS::DCLsym->new;
        return $command if scalar $syms->getsym( uc $command );
    }

    require Config;
    require File::Spec;
    require ExtUtils::MakeMaker;

    my @possibles;

    if( File::Spec->file_name_is_absolute($command) ) {
        return MM->maybe_command($command);

    } else {
        for my $dir (
            (split /\Q$Config::Config{path_sep}\E/, $ENV{PATH}),
            File::Spec->curdir
        ) {
            next if ! $dir || ! -d $dir;
            my $abs = File::Spec->catfile( IS_WIN32 ? Win32::GetShortPathName( $dir ) : $dir, $command);
            push @possibles, $abs if $abs = MM->maybe_command($abs);
        }
    }
    return @possibles if wantarray and $INSTANCES;
    return shift @possibles;
}

=head2 $ok | ($ok, $err, $full_buf, $stdout_buff, $stderr_buff) = run( command => COMMAND, [verbose => BOOL, buffer => \$SCALAR, timeout => DIGIT] );

C<run> takes 4 arguments:

=over 4

=item command

This is the command to execute. It may be either a string or an array
reference.
This is a required argument.

See L<"Caveats"> for remarks on how commands are parsed and their
limitations.

=item verbose

This controls whether all output of a command should also be printed
to STDOUT/STDERR or should only be trapped in buffers (NOTE: buffers
require L<IPC::Run> to be installed, or your system able to work with
L<IPC::Open3>).

It will default to the global setting of C<$IPC::Cmd::VERBOSE>,
which by default is 0.

=item buffer

This will hold all the output of a command. It needs to be a reference
to a scalar.
Note that this will hold both the STDOUT and STDERR messages, and you
have no way of telling which is which.
If you require this distinction, run the C<run> command in list context
and inspect the individual buffers.

Of course, this requires that the underlying call supports buffers. See
the note on buffers above.

=item timeout

Sets the maximum time the command is allowed to run before aborting,
using the built-in C<alarm()> call. If the timeout is triggered, the
C<errorcode> in the return value will be set to an object of the
C<IPC::Cmd::TimeOut> class. See the L<"error message"> section below for
details.

Defaults to C<0>, meaning no timeout is set.

=back

C<run> will return a simple C<true> or C<false> when called in scalar
context.
In list context, you will be returned a list of the following items:

=over 4

=item success

A simple boolean indicating if the command executed without errors or
not.

=item error message

If the first element of the return value (C<success>) was 0, then some
error occurred. This second element is the error message the command
you requested exited with, if available. This is generally a pretty
printed value of C<$?> or C<$@>. See C<perldoc perlvar> for details on
what they can contain.
If the error was a timeout, the C<error message> will be prefixed with
the string C<IPC::Cmd::TimeOut>, the timeout class.

=item full_buffer

This is an array reference containing all the output the command
generated.
Note that buffers are only available if you have L<IPC::Run> installed,
or if your system is able to work with L<IPC::Open3> -- see below).
Otherwise, this element will be C<undef>.

=item out_buffer

This is an array reference containing all the output sent to STDOUT the
command generated. The notes from L<"full_buffer"> apply.

inc/inc_IPC-Cmd/IPC/Cmd.pm  view on Meta::CPAN

  my( $i, $quote_mode ) = ( 0, 0 );

  while ( $i < length() ) {

    my $ch      = substr( $_, $i  , 1 );
    my $next_ch = substr( $_, $i+1, 1 );

    if ( $ch eq '\\' && $next_ch eq '"' ) {
      $arg .= '"';
      $i++;
    } elsif ( $ch eq '\\' && $next_ch eq '\\' ) {
      $arg .= '\\';
      $i++;
    } elsif ( $ch eq '"' && $next_ch eq '"' && $quote_mode ) {
      $quote_mode = !$quote_mode;
      $arg .= '"';
      $i++;
    } elsif ( $ch eq '"' && $next_ch eq '"' && !$quote_mode &&
          ( $i + 2 == length()  ||
        substr( $_, $i + 2, 1 ) eq ' ' )
        ) { # for cases like: a"" => [ 'a' ]
      push( @argv, $arg );
      $arg = '';
      $i += 2;
    } elsif ( $ch eq '"' ) {
      $quote_mode = !$quote_mode;
    } elsif ( $ch eq ' ' && !$quote_mode ) {
      push( @argv, $arg ) if defined( $arg ) && length( $arg );
      $arg = '';
      ++$i while substr( $_, $i + 1, 1 ) eq ' ';
    } else {
      $arg .= $ch;
    }

    $i++;
  }

  push( @argv, $arg ) if defined( $arg ) && length( $arg );
  return @argv;
}



{   use File::Spec;
    use Symbol;

    my %Map = (
        STDOUT => [qw|>&|, \*STDOUT, Symbol::gensym() ],
        STDERR => [qw|>&|, \*STDERR, Symbol::gensym() ],
        STDIN  => [qw|<&|, \*STDIN,  Symbol::gensym() ],
    );

    ### dups FDs and stores them in a cache
    sub __dup_fds {
        my $self    = shift;
        my @fds     = @_;

        __PACKAGE__->_debug( "# Closing the following fds: @fds" ) if $DEBUG;

        for my $name ( @fds ) {
            my($redir, $fh, $glob) = @{$Map{$name}} or (
                Carp::carp(loc("No such FD: '%1'", $name)), next );

            ### MUST use the 2-arg version of open for dup'ing for
            ### 5.6.x compatibility. 5.8.x can use 3-arg open
            ### see perldoc5.6.2 -f open for details
            open $glob, $redir . fileno($fh) or (
                        Carp::carp(loc("Could not dup '$name': %1", $!)),
                        return
                    );

            ### we should re-open this filehandle right now, not
            ### just dup it
            ### Use 2-arg version of open, as 5.5.x doesn't support
            ### 3-arg version =/
            if( $redir eq '>&' ) {
                open( $fh, '>' . File::Spec->devnull ) or (
                    Carp::carp(loc("Could not reopen '$name': %1", $!)),
                    return
                );
            }
        }

        return 1;
    }

    ### reopens FDs from the cache
    sub __reopen_fds {
        my $self    = shift;
        my @fds     = @_;

        __PACKAGE__->_debug( "# Reopening the following fds: @fds" ) if $DEBUG;

        for my $name ( @fds ) {
            my($redir, $fh, $glob) = @{$Map{$name}} or (
                Carp::carp(loc("No such FD: '%1'", $name)), next );

            ### MUST use the 2-arg version of open for dup'ing for
            ### 5.6.x compatibility. 5.8.x can use 3-arg open
            ### see perldoc5.6.2 -f open for details
            open( $fh, $redir . fileno($glob) ) or (
                    Carp::carp(loc("Could not restore '$name': %1", $!)),
                    return
                );

            ### close this FD, we're not using it anymore
            close $glob;
        }
        return 1;

    }
}

sub _debug {
    my $self    = shift;
    my $msg     = shift or return;
    my $level   = shift || 0;

    local $Carp::CarpLevel += $level;
    Carp::carp($msg);

    return 1;
}

sub _pp_child_error {
    my $self    = shift;
    my $cmd     = shift or return;
    my $ce      = shift or return;
    my $pp_cmd  = ref $cmd ? "@$cmd" : $cmd;


    my $str;
    if( $ce == -1 ) {
        ### Include $! in the error message, so that the user can
        ### see 'No such file or directory' versus 'Permission denied'
        ### versus 'Cannot fork' or whatever the cause was.
        $str = "Failed to execute '$pp_cmd': $!";

    } elsif ( $ce & 127 ) {
        ### some signal
        $str = loc( "'%1' died with signal %d, %s coredump\n",
               $pp_cmd, ($ce & 127), ($ce & 128) ? 'with' : 'without');

    } else {
        ### Otherwise, the command run but gave error status.
        $str = "'$pp_cmd' exited with value " . ($ce >> 8);
    }

    $self->_debug( "# Child error '$ce' translated to: $str" ) if $DEBUG;

    return $str;
}

1;

=head2 $q = QUOTE

Returns the character used for quoting strings on this platform. This is
usually a C<'> (single quote) on most systems, but some systems use different
quotes. For example, C<Win32> uses C<"> (double quote).

You can use it as follows:

  use IPC::Cmd qw[run QUOTE];
  my $cmd = q[echo ] . QUOTE . q[foo bar] . QUOTE;

This makes sure that C<foo bar> is treated as a string, rather than two
separate arguments to the C<echo> function.

__END__

=head1 HOW IT WORKS

C<run> will try to execute your command using the following logic:

=over 4

=item *

If you have C<IPC::Run> installed, and the variable C<$IPC::Cmd::USE_IPC_RUN>
is set to true (See the L<"Global Variables"> section) use that to execute
the command. You will have the full output available in buffers, interactive commands
are sure to work  and you are guaranteed to have your verbosity
settings honored cleanly.

=item *

Otherwise, if the variable C<$IPC::Cmd::USE_IPC_OPEN3> is set to true
(See the L<"Global Variables"> section), try to execute the command using
L<IPC::Open3>. Buffers will be available on all platforms,
interactive commands will still execute cleanly, and also your verbosity
settings will be adhered to nicely;

=item *

Otherwise, if you have the C<verbose> argument set to true, we fall back
to a simple C<system()> call. We cannot capture any buffers, but
interactive commands will still work.

=item *

Otherwise we will try and temporarily redirect STDERR and STDOUT, do a
C<system()> call with your command and then re-open STDERR and STDOUT.
This is the method of last resort and will still allow you to execute
your commands cleanly. However, no buffers will be available.

=back

=head1 Global Variables

The behaviour of IPC::Cmd can be altered by changing the following
global variables:

=head2 $IPC::Cmd::VERBOSE

This controls whether IPC::Cmd will print any output from the
commands to the screen or not. The default is 0.

=head2 $IPC::Cmd::USE_IPC_RUN

This variable controls whether IPC::Cmd will try to use L<IPC::Run>
when available and suitable.

=head2 $IPC::Cmd::USE_IPC_OPEN3

This variable controls whether IPC::Cmd will try to use L<IPC::Open3>
when available and suitable. Defaults to true.

=head2 $IPC::Cmd::WARN

This variable controls whether run-time warnings should be issued, like
the failure to load an C<IPC::*> module you explicitly requested.

Defaults to true. Turn this off at your own risk.

=head2 $IPC::Cmd::INSTANCES

This variable controls whether C<can_run> will return all instances of
the binary it finds in the C<PATH> when called in a list context.

Defaults to false, set to true to enable the described behaviour.

=head2 $IPC::Cmd::ALLOW_NULL_ARGS

This variable controls whether C<run> will remove any empty/null arguments
it finds in command arguments.

Defaults to false, so it will remove null arguments. Set to true to allow
them.

=head1 Caveats

=over 4

=item Whitespace and IPC::Open3 / system()

When using C<IPC::Open3> or C<system>, if you provide a string as the
C<command> argument, it is assumed to be appropriately escaped. You can
use the C<QUOTE> constant to use as a portable quote character (see above).
However, if you provide an array reference, special rules apply:

If your command contains B<special characters> (< > | &), it will
be internally stringified before executing the command, to avoid that these
special characters are escaped and passed as arguments instead of retaining
their special meaning.

However, if the command contained arguments that contained whitespace,
stringifying the command would loose the significance of the whitespace.
Therefore, C<IPC::Cmd> will quote any arguments containing whitespace in your
command if the command is passed as an arrayref and contains special characters.

=item Whitespace and IPC::Run