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package IPC::System::Simple;
# ABSTRACT: Run commands simply, with detailed diagnostics
use 5.006;
use strict;
use warnings;
use re 'taint';
use Carp;
use List::Util qw(first);
use Scalar::Util qw(tainted);
use Config;
use constant WINDOWS => ($^O eq 'MSWin32');
use constant VMS => ($^O eq 'VMS');
BEGIN {
# It would be lovely to use the 'if' module here, but it didn't
# enter core until 5.6.2, and we want to keep 5.6.0 compatibility.
if (WINDOWS) {
## no critic (ProhibitStringyEval)
eval q{
use Win32::Process qw(INFINITE NORMAL_PRIORITY_CLASS);
use File::Spec;
use Win32;
# This uses the same rules as the core win32.c/get_shell() call.
use constant WINDOWS_SHELL => eval { Win32::IsWinNT() }
? [ qw(cmd.exe /x/d/c) ]
: [ qw(command.com /c) ];
# These are used when invoking _win32_capture
use constant NO_SHELL => 0;
use constant USE_SHELL => 1;
};
## use critic
# Die nosily if any of the above broke.
die $@ if $@;
}
}
# Note that we don't use WIFSTOPPED because perl never uses
# the WUNTRACED flag, and hence will never return early from
# system() if the child processes is suspended with a SIGSTOP.
use POSIX qw(WIFEXITED WEXITSTATUS WIFSIGNALED WTERMSIG);
use constant FAIL_START => q{"%s" failed to start: "%s"};
use constant FAIL_PLUMBING => q{Error in IPC::System::Simple plumbing: "%s" - "%s"};
use constant FAIL_CMD_BLANK => q{Entirely blank command passed: "%s"};
use constant FAIL_INTERNAL => q{Internal error in IPC::System::Simple: "%s"};
use constant FAIL_TAINT => q{%s called with tainted argument "%s"};
use constant FAIL_TAINT_ENV => q{%s called with tainted environment $ENV{%s}};
use constant FAIL_SIGNAL => q{"%s" died to signal "%s" (%d)%s};
use constant FAIL_BADEXIT => q{"%s" unexpectedly returned exit value %d};
use constant FAIL_UNDEF => q{%s called with undefined command};
use constant FAIL_POSIX => q{IPC::System::Simple does not understand the POSIX error '%s'. Please check http://search.cpan.org/perldoc?IPC::System::Simple to see if there is an updated version. If not please report this as a bug to http://rt.cpan.org/Public/Bug/Report.html?Queue=IPC-System-Simple};
# On Perl's older than 5.8.x we can't assume that there'll be a
# $^{TAINT} for us to check, so we assume that our args may always
# be tainted.
use constant ASSUME_TAINTED => ($] < 5.008);
use constant EXIT_ANY_CONST => -1; # Used internally
use constant EXIT_ANY => [ EXIT_ANY_CONST ]; # Exported
use constant UNDEFINED_POSIX_RE => qr{not (?:defined|a valid) POSIX macro|not implemented on this architecture};
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw(
capture capturex
run runx
system systemx
$EXITVAL EXIT_ANY
);
our $VERSION = '1.25'; # VERSION : From dzil
our $EXITVAL = -1;
my @Signal_from_number = split(' ', $Config{sig_name});
# Environment variables we don't want to see tainted.
my @Check_tainted_env = qw(PATH IFS CDPATH ENV BASH_ENV);
if (WINDOWS) {
push(@Check_tainted_env, 'PERL5SHELL');
}
if (VMS) {
push(@Check_tainted_env, 'DCL$PATH');
}
# Not all systems implement the WIFEXITED calls, but POSIX
# will always export them (even if they're just stubs that
# die with an error). Test for the presence of a working
# WIFEXITED and friends, or define our own.
eval { WIFEXITED(0); };
if ($@ =~ UNDEFINED_POSIX_RE) {
no warnings 'redefine'; ## no critic
*WIFEXITED = sub { not $_[0] & 0xff };
*WEXITSTATUS = sub { $_[0] >> 8 };
*WIFSIGNALED = sub { $_[0] & 127 };
*WTERMSIG = sub { $_[0] & 127 };
} elsif ($@) {
croak sprintf FAIL_POSIX, $@;
}
# None of the POSIX modules I've found define WCOREDUMP, although
# many systems define it. Check the POSIX module in the hope that
# it may actually be there.
# TODO: Ideally, $NATIVE_WCOREDUMP should be a constant.
my $NATIVE_WCOREDUMP;
eval { POSIX::WCOREDUMP(1); };
if ($@ =~ UNDEFINED_POSIX_RE) {
*WCOREDUMP = sub { $_[0] & 128 };
$NATIVE_WCOREDUMP = 0;
} elsif ($@) {
croak sprintf FAIL_POSIX, $@;
} else {
# POSIX actually has it defined! Huzzah!
*WCOREDUMP = \&POSIX::WCOREDUMP;
$NATIVE_WCOREDUMP = 1;
}
sub _native_wcoredump {
return $NATIVE_WCOREDUMP;
}
# system simply calls run
*system = \&run;
*systemx = \&runx;
# run is our way of running a process with system() semantics
sub run {
_check_taint(@_);
my ($valid_returns, $command, @args) = _process_args(@_);
# If we have arguments, we really want to call systemx,
# so we do so.
if (@args) {
return systemx($valid_returns, $command, @args);
}
# Without arguments, we're calling system, and checking
# the results.
# We're throwing our own exception on command not found, so
# we don't need a warning from Perl.
{
# silence 'Statement unlikely to be reached' warning
no warnings 'exec'; ## no critic
CORE::system($command,@args);
}
return _process_child_error($?,$command,$valid_returns);
}
# runx is just like system/run, but *never* invokes the shell.
sub runx {
_check_taint(@_);
my ($valid_returns, $command, @args) = _process_args(@_);
if (WINDOWS) {
our $EXITVAL = -1;
my $pid = _spawn_or_die($command, "$command @args");
$pid->Wait(INFINITE); # Wait for process exit.
$pid->GetExitCode($EXITVAL);
return _check_exit($command,$EXITVAL,$valid_returns);
}
# If system() fails, we throw our own exception. We don't
# need to have perl complain about it too.
no warnings; ## no critic
CORE::system { $command } $command, @args;
return _process_child_error($?, $command, $valid_returns);
}
# capture is our way of running a process with backticks/qx semantics
sub capture {
_check_taint(@_);
my ($valid_returns, $command, @args) = _process_args(@_);
if (@args) {
return capturex($valid_returns, $command, @args);
}
if (WINDOWS) {
# USE_SHELL really means "You may use the shell if you need it."
return _win32_capture(USE_SHELL, $valid_returns, $command, @args);
}
our $EXITVAL = -1;
my $wantarray = wantarray();
# We'll produce our own warnings on failure to execute.
no warnings 'exec'; ## no critic
if ($wantarray) {
my @results = qx($command);
_process_child_error($?,$command,$valid_returns);
return @results;
}
my $results = qx($command);
_process_child_error($?,$command,$valid_returns);
return $results;
}
# _win32_capture implements the capture and capurex commands on Win32.
# We need to wrap the whole internals of this sub into
# an if (WINDOWS) block to avoid it being compiled on non-Win32 systems.
sub _win32_capture {
if (not WINDOWS) {
croak sprintf(FAIL_INTERNAL, "_win32_capture called when not under Win32");
} else {
my ($use_shell, $valid_returns, $command, @args) = @_;
my $wantarray = wantarray();
# Perl doesn't support multi-arg open under
# Windows. Perl also doesn't provide very good
# feedback when normal backtails fail, either;
# it returns exit status from the shell
# (which is indistinguishable from the command
# running and producing the same exit status).
# As such, we essentially have to write our own
# backticks.
# We start by dup'ing STDOUT.
open(my $saved_stdout, '>&', \*STDOUT) ## no critic
or croak sprintf(FAIL_PLUMBING, "Can't dup STDOUT", $!);
# We now open up a pipe that will allow us to
# communicate with the new process.
pipe(my ($read_fh, $write_fh))
or croak sprintf(FAIL_PLUMBING, "Can't create pipe", $!);
# Allow CRLF sequences to become "\n", since
# this is what Perl backticks do.
binmode($read_fh, ':crlf');
# Now we re-open our STDOUT to $write_fh...
open(STDOUT, '>&', $write_fh) ## no critic
or croak sprintf(FAIL_PLUMBING, "Can't redirect STDOUT", $!);
# If we have args, or we're told not to use the shell, then
# we treat $command as our shell. Otherwise we grub around
# in our command to look for a command to run.
#
# Note that we don't actually *use* the shell (although in
# a future version we might). Being told not to use the shell
# (capturex) means we treat our command as really being a command,
# and not a command line.
my $exe = @args ? $command :
(! $use_shell) ? $command :
$command =~ m{^"([^"]+)"}x ? $1 :
$command =~ m{(\S+) }x ? $1 :
croak sprintf(FAIL_CMD_BLANK, $command);
# And now we spawn our new process with inherited
# filehandles.
my $err;
my $pid = eval {
_spawn_or_die($exe, "$command @args");
}
or do {
$err = $@;
};
# Regardless of whether our command ran, we must restore STDOUT.
# RT #48319
open(STDOUT, '>&', $saved_stdout) ## no critic
or croak sprintf(FAIL_PLUMBING,"Can't restore STDOUT", $!);
# And now, if there was an actual error , propagate it.
die $err if defined $err; # If there's an error from _spawn_or_die
# Clean-up the filehandles we no longer need...
close($write_fh)
or croak sprintf(FAIL_PLUMBING,q{Can't close write end of pipe}, $!);
close($saved_stdout)
or croak sprintf(FAIL_PLUMBING,q{Can't close saved STDOUT}, $!);
# Read the data from our child...
my (@results, $result);
if ($wantarray) {
@results = <$read_fh>;
} else {
$result = join("",<$read_fh>);
}
# Tidy up our windows process and we're done!
$pid->Wait(INFINITE); # Wait for process exit.
$pid->GetExitCode($EXITVAL);
_check_exit($command,$EXITVAL,$valid_returns);
return $wantarray ? @results : $result;
}
}
# capturex() is just like backticks/qx, but never invokes the shell.
sub capturex {
_check_taint(@_);
my ($valid_returns, $command, @args) = _process_args(@_);
our $EXITVAL = -1;
my $wantarray = wantarray();
if (WINDOWS) {
return _win32_capture(NO_SHELL, $valid_returns, $command, @args);
}
# We can't use a multi-arg piped open here, since 5.6.x
# doesn't like them. Instead we emulate what 5.8.x does,
# which is to create a pipe(), set the close-on-exec flag
# on the child, and the fork/exec. If the exec fails, the
# child writes to the pipe. If the exec succeeds, then
# the pipe closes without data.
pipe(my ($read_fh, $write_fh))
or croak sprintf(FAIL_PLUMBING, "Can't create pipe", $!);
# This next line also does an implicit fork.
my $pid = open(my $pipe, '-|'); ## no critic
if (not defined $pid) {
croak sprintf(FAIL_START, $command, $!);
} elsif (not $pid) {
# Child process, execs command.
close($read_fh);
# TODO: 'no warnings exec' doesn't get rid
# of the 'unlikely to be reached' warnings.
# This is a bug in perl / perldiag / perllexwarn / warnings.
no warnings; ## no critic
CORE::exec { $command } $command, @args;
# Oh no, exec fails! Send the reason why to
# the parent.
print {$write_fh} int($!);
exit(-1);
}
{
# In parent process.
close($write_fh);
# Parent process, check for child error.
my $error = <$read_fh>;
# Tidy up our pipes.
close($read_fh);
# Check for error.
if ($error) {
# Setting $! to our child error number gives
# us nice looking strings when printed.
local $! = $error;
croak sprintf(FAIL_START, $command, $!);
}
}
# Parent process, we don't care about our pid, but we
# do go and read our pipe.
if ($wantarray) {
my @results = <$pipe>;
close($pipe);
_process_child_error($?,$command,$valid_returns);
return @results;
}
# NB: We don't check the return status on close(), since
# on failure it sets $?, which we then inspect for more
# useful information.
my $results = join("",<$pipe>);
close($pipe);
_process_child_error($?,$command,$valid_returns);
return $results;
}
# Tries really hard to spawn a process under Windows. Returns
# the pid on success, or undef on error.
sub _spawn_or_die {
# We need to wrap practically the entire sub in an
# if block to ensure it doesn't get compiled under non-Win32
# systems. Compiling on these systems would not only be a
# waste of time, but also results in complaints about
# the NORMAL_PRIORITY_CLASS constant.
if (not WINDOWS) {
croak sprintf(FAIL_INTERNAL, "_spawn_or_die called when not under Win32");
} else {
my ($orig_exe, $cmdline) = @_;
my $pid;
my $exe = $orig_exe;
# If our command doesn't have an extension, add one.
$exe .= $Config{_exe} if ($exe !~ m{\.});
Win32::Process::Create(
$pid, $exe, $cmdline, 1, NORMAL_PRIORITY_CLASS, "."
) and return $pid;
my @path = split(/;/,$ENV{PATH});
foreach my $dir (@path) {
my $fullpath = File::Spec->catfile($dir,$exe);
# We're using -x here on the assumption that stat()
# is faster than spawn, so trying to spawn a process
# for each path element will be unacceptably
# inefficient.
if (-x $fullpath) {
Win32::Process::Create(
$pid, $fullpath, $cmdline, 1,
NORMAL_PRIORITY_CLASS, "."
) and return $pid;
}
}
croak sprintf(FAIL_START, $orig_exe, $^E);
}
}
# Complain on tainted arguments or environment.
# ASSUME_TAINTED is true for 5.6.x, since it's missing ${^TAINT}
sub _check_taint {
return if not (ASSUME_TAINTED or ${^TAINT});
my $caller = (caller(1))[3];
foreach my $var (@_) {
if (tainted $var) {
croak sprintf(FAIL_TAINT, $caller, $var);
}
}
foreach my $var (@Check_tainted_env) {
if (tainted $ENV{$var} ) {
croak sprintf(FAIL_TAINT_ENV, $caller, $var);
}
}
return;
}
# This subroutine performs the difficult task of interpreting
# $?. It's not intended to be called directly, as it will
# croak on errors, and its implementation and interface may
# change in the future.
sub _process_child_error {
my ($child_error, $command, $valid_returns) = @_;
$EXITVAL = -1;
my $coredump = WCOREDUMP($child_error);
# There's a bug in perl 5.10.0 where if the system
# does not provide a native WCOREDUMP, then $? will
# never contain coredump information. This code
# checks to see if we have the bug, and works around
# it if needed.
if ($] >= 5.010 and not $NATIVE_WCOREDUMP) {
$coredump ||= WCOREDUMP( ${^CHILD_ERROR_NATIVE} );
}
if ($child_error == -1) {
croak sprintf(FAIL_START, $command, $!);
} elsif ( WIFEXITED( $child_error ) ) {
$EXITVAL = WEXITSTATUS( $child_error );
return _check_exit($command,$EXITVAL,$valid_returns);
} elsif ( WIFSIGNALED( $child_error ) ) {
my $signal_no = WTERMSIG( $child_error );
my $signal_name = $Signal_from_number[$signal_no] || "UNKNOWN";
croak sprintf FAIL_SIGNAL, $command, $signal_name, $signal_no, ($coredump ? " and dumped core" : "");
}
croak sprintf(FAIL_INTERNAL, qq{'$command' ran without exit value or signal});
}
# A simple subroutine for checking exit values. Results in better
# assurance of consistent error messages, and better forward support
# for new features in I::S::S.
sub _check_exit {
my ($command, $exitval, $valid_returns) = @_;
# If we have a single-value list consisting of the EXIT_ANY
# value, then we're happy with whatever exit value we're given.
if (@$valid_returns == 1 and $valid_returns->[0] == EXIT_ANY_CONST) {
return $exitval;
}
if (not defined first { $_ == $exitval } @$valid_returns) {
croak sprintf FAIL_BADEXIT, $command, $exitval;
}
return $exitval;
}
# This subroutine simply determines a list of valid returns, the command
# name, and any arguments that we need to pass to it.
sub _process_args {
my $valid_returns = [ 0 ];
my $caller = (caller(1))[3];
if (not @_) {
croak "$caller called with no arguments";
}
if (ref $_[0] eq "ARRAY") {
$valid_returns = shift(@_);
}
if (not @_) {
croak "$caller called with no command";
}
my $command = shift(@_);
if (not defined $command) {
croak sprintf( FAIL_UNDEF, $caller );
}
return ($valid_returns,$command,@_);
}
1;
__END__
=head1 NAME
IPC::System::Simple - Run commands simply, with detailed diagnostics
=head1 SYNOPSIS
use IPC::System::Simple qw(system systemx capture capturex);
system("some_command"); # Command succeeds or dies!
system("some_command",@args); # Succeeds or dies, avoids shell if @args
systemx("some_command",@args); # Succeeds or dies, NEVER uses the shell
# Capture the output of a command (just like backticks). Dies on error.
my $output = capture("some_command");
# Just like backticks in list context. Dies on error.
my @output = capture("some_command");
# As above, but avoids the shell if @args is non-empty
my $output = capture("some_command", @args);
# As above, but NEVER invokes the shell.
my $output = capturex("some_command", @args);
my @output = capturex("some_command", @args);
=head1 DESCRIPTION
Calling Perl's in-built C<system()> function is easy,
determining if it was successful is I<hard>. Let's face it,
C<$?> isn't the nicest variable in the world to play with, and
even if you I<do> check it, producing a well-formatted error
string takes a lot of work.
C<IPC::System::Simple> takes the hard work out of calling
external commands. In fact, if you want to be really lazy,
you can just write:
use IPC::System::Simple qw(system);
and all of your C<system> commands will either succeed (run to
completion and return a zero exit value), or die with rich diagnostic
messages.
The C<IPC::System::Simple> module also provides a simple replacement
to Perl's backticks operator. Simply write:
use IPC::System::Simple qw(capture);
and then use the L</capture()> command just like you'd use backticks.
If there's an error, it will die with a detailed description of what
went wrong. Better still, you can even use C<capturex()> to run the
equivalent of backticks, but without the shell:
use IPC::System::Simple qw(capturex);
my $result = capturex($command, @args);
If you want more power than the basic interface, including the
ability to specify which exit values are acceptable, trap errors,
or process diagnostics, then read on!
=head1 ADVANCED SYNOPSIS
use IPC::System::Simple qw(
capture capturex system systemx run runx $EXITVAL EXIT_ANY
);
# Run a command, throwing exception on failure
run("some_command");
runx("some_command",@args); # Run a command, avoiding the shell
# Do the same thing, but with the drop-in system replacement.
system("some_command");
systemx("some_command", @args);
# Run a command which must return 0..5, avoid the shell, and get the
# exit value (we could also look at $EXITVAL)
my $exit_value = runx([0..5], "some_command", @args);
# The same, but any exit value will do.
my $exit_value = runx(EXIT_ANY, "some_command", @args);
# Capture output into $result and throw exception on failure
my $result = capture("some_command");
# Check exit value from captured command
print "some_command exited with status $EXITVAL\n";
# Captures into @lines, splitting on $/
my @lines = capture("some_command");
# Run a command which must return 0..5, capture the output into
# @lines, and avoid the shell.
my @lines = capturex([0..5], "some_command", @args);
=head1 ADVANCED USAGE
=head2 run() and system()
C<IPC::System::Simple> provides a subroutine called
C<run>, that executes a command using the same semantics is
Perl's built-in C<system>:
use IPC::System::Simple qw(run);
run("cat *.txt"); # Execute command via the shell
run("cat","/etc/motd"); # Execute command without shell
The primary difference between Perl's in-built system and
the C<run> command is that C<run> will throw an exception on
failure, and allows a list of acceptable exit values to be set.
See L</Exit values> for further information.
In fact, you can even have C<IPC::System::Simple> replace the
default C<system> function for your package so it has the
same behaviour:
use IPC::System::Simple qw(system);
system("cat *.txt"); # system now suceeds or dies!
C<system> and C<run> are aliases to each other.
See also L</runx(), systemx() and capturex()> for variants of
C<system()> and C<run()> that never invoke the shell, even with
a single argument.
=head2 capture()
A second subroutine, named C<capture> executes a command with
the same semantics as Perl's built-in backticks (and C<qx()>):
use IPC::System::Simple qw(capture);
# Capture text while invoking the shell.
my $file = capture("cat /etc/motd");
my @lines = capture("cat /etc/passwd");
However unlike regular backticks, which always use the shell, C<capture>
will bypass the shell when called with multiple arguments:
# Capture text while avoiding the shell.
my $file = capture("cat", "/etc/motd");
my @lines = capture("cat", "/etc/passwd");
See also L</runx(), systemx() and capturex()> for a variant of
C<capture()> that never invokes the shell, even with a single
argument.
=head2 runx(), systemx() and capturex()
The C<runx()>, C<systemx()> and C<capturex()> commands are identical
to the multi-argument forms of C<run()>, C<system()> and C<capture()>
respectively, but I<never> invoke the shell, even when called with a
single argument. These forms are particularly useful when a command's
argument list I<might> be empty, for example:
systemx($cmd, @args);
The use of C<systemx()> here guarantees that the shell will I<never>
be invoked, even if C<@args> is empty.
=head2 Exception handling
In the case where the command returns an unexpected status, both C<run> and
C<capture> will throw an exception, which if not caught will terminate your
program with an error.
Capturing the exception is easy:
eval {
run("cat *.txt");
};
if ($@) {
print "Something went wrong - $@\n";
}
See the diagnostics section below for more details.
=head3 Exception cases
C<IPC::System::Simple> considers the following to be unexpected,
and worthy of exception:
=over 4
=item *
Failing to start entirely (eg, command not found, permission denied).
=item *
Returning an exit value other than zero (but see below).
=item *
Being killed by a signal.
=item *
Being passed tainted data (in taint mode).
=back
=head2 Exit values
Traditionally, system commands return a zero status for success and a
non-zero status for failure. C<IPC::System::Simple> will default to throwing
an exception if a non-zero exit value is returned.
You may specify a range of values which are considered acceptable exit
values by passing an I<array reference> as the first argument. The
special constant C<EXIT_ANY> can be used to allow I<any> exit value
to be returned.
use IPC::System::Simple qw(run system capture EXIT_ANY);
run( [0..5], "cat *.txt"); # Exit values 0-5 are OK
system( [0..5], "cat *.txt"); # This works the same way
my @lines = capture( EXIT_ANY, "cat *.txt"); # Any exit is fine.
The C<run> and replacement C<system> subroutines returns the exit
value of the process:
my $exit_value = run( [0..5], "cat *.txt");
# OR:
my $exit_value = system( [0..5] "cat *.txt");
print "Program exited with value $exit_value\n";
=head3 $EXITVAL
The exit value of any command executed by C<IPC::System::Simple>
can always be retrieved from the C<$IPC::System::Simple::EXITVAL>
variable:
This is particularly useful when inspecting results from C<capture>,
which returns the captured text from the command.
use IPC::System::Simple qw(capture $EXITVAL EXIT_ANY);
my @enemies_defeated = capture(EXIT_ANY, "defeat_evil", "/dev/mordor");
print "Program exited with value $EXITVAL\n";
C<$EXITVAL> will be set to C<-1> if the command did not exit normally (eg,
being terminated by a signal) or did not start. In this situation an
exception will also be thrown.
=head2 WINDOWS-SPECIFIC NOTES
As of C<IPC::System::Simple> v0.06, the C<run> subroutine I<when
called with multiple arguments> will make available the full 32-bit
exit value on Win32 systems. This is different from the
previous versions of C<IPC::System::Simple> and from Perl's
in-build C<system()> function, which can only handle 8-bit return values.
The C<capture> subroutine always returns the 32-bit exit value under
Windows. The C<capture> subroutine also never uses the shell,
even when passed a single argument.
Versions of C<IPC::System::Simple> before v0.09 would not search
the C<PATH> environment variable when the multi-argument form of
C<run()> was called. Versions from v0.09 onwards correctly search
the path provided the command is provided including the extension
(eg, C<notepad.exe> rather than just C<notepad>, or C<gvim.bat> rather
than just C<gvim>). If no extension is provided, C<.exe> is
assumed.
Signals are not supported on Windows systems. Sending a signal
to a Windows process will usually cause it to exit with the signal
number used.
=head1 DIAGNOSTICS
=over 4
=item "%s" failed to start: "%s"
The command specified did not even start. It may not exist, or
you may not have permission to use it. The reason it could not
start (as determined from C<$!>) will be provided.
=item "%s" unexpectedly returned exit value %d
The command ran successfully, but returned an exit value we did
not expect. The value returned is reported.
=item "%s" died to signal "%s" (%d) %s
The command was killed by a signal. The name of the signal
will be reported, or C<UNKNOWN> if it cannot be determined. The
signal number is always reported. If we detected that the
process dumped core, then the string C<and dumped core> is
appended.
=item IPC::System::Simple::%s called with no arguments
You attempted to call C<run> or C<capture> but did not provide any
arguments at all. At the very lease you need to supply a command
to run.
=item IPC::System::Simple::%s called with no command
You called C<run> or C<capture> with a list of acceptable exit values,
but no actual command.
=item IPC::System::Simple::%s called with tainted argument "%s"
You called C<run> or C<capture> with tainted (untrusted) arguments, which is
almost certainly a bad idea. To untaint your arguments you'll need to pass
your data through a regular expression and use the resulting match variables.
See L<perlsec/Laundering and Detecting Tainted Data> for more information.
=item IPC::System::Simple::%s called with tainted environment $ENV{%s}
You called C<run> or C<capture> but part of your environment was tainted
(untrusted). You should either delete the named environment
variable before calling C<run>, or set it to an untainted value
(usually one set inside your program). See
L<perlsec/Cleaning Up Your Path> for more information.
=item Error in IPC::System::Simple plumbing: "%s" - "%s"
Implementing the C<capture> command involves dark and terrible magicks
involving pipes, and one of them has sprung a leak. This could be due to a
lack of file descriptors, although there are other possibilities.
If you are able to reproduce this error, you are encouraged
to submit a bug report according to the L</Reporting bugs> section below.
=item Internal error in IPC::System::Simple: "%s"
You've found a bug in C<IPC::System::Simple>. Please check to
see if an updated version of C<IPC::System::Simple> is available.
If not, please file a bug report according to the L</Reporting bugs> section
below.
=item IPC::System::Simple::%s called with undefined command
You've passed the undefined value as a command to be executed.
While this is a very Zen-like action, it's not supported by
Perl's current implementation.
=back
=head1 DEPENDENCIES
This module depends upon L<Win32::Process> when used on Win32
system. C<Win32::Process> is bundled as a core module in ActivePerl 5.6
and above.
There are no non-core dependencies on non-Win32 systems.
=head1 COMPARISON TO OTHER APIs
Perl provides a range of in-built functions for handling external
commands, and CPAN provides even more. The C<IPC::System::Simple>
differentiates itself from other options by providing:
=over 4
=item Extremely detailed diagnostics
The diagnostics produced by C<IPC::System::Simple> are designed
to provide as much information as possible. Rather than requiring
the developer to inspect C<$?>, C<IPC::System::Simple> does the
hard work for you.
If an odd exit status is provided, you're informed of what it is. If
a signal kills your process, you are informed of both its name and
number. If tainted data or environment prevents your command from
running, you are informed of exactly which datais
=item Exceptions on failure
C<IPC::System::Simple> takes an aggressive approach to error handling.
Rather than allow commands to fail silently, exceptions are thrown
when unexpected results are seen. This allows for easy development
using a try/catch style, and avoids the possibility of accidently
continuing after a failed command.
=item Easy access to exit status
The C<run>, C<system> and C<capture> commands all set C<$EXITVAL>,
making it easy to determine the exit status of a command.
Additionally, the C<system> and C<run> interfaces return the exit
status.
=item Consistent interfaces
When called with multiple arguments, the C<run>, C<system> and
C<capture> interfaces I<never> invoke the shell. This differs
from the in-built Perl C<system> command which may invoke the
shell under Windows when called with multiple arguments. It
differs from the in-built Perl backticks operator which always
invokes the shell.
=back
=head1 BUGS
When C<system> is exported, the exotic form C<system { $cmd } @args>
is not supported. Attemping to use the exotic form is a syntax
error. This affects the calling package I<only>. Use C<CORE::system>
if you need it, or consider using the L<autodie> module to replace
C<system> with lexical scope.
Core dumps are only checked for when a process dies due to a
signal. It is not believed there are any systems where processes
can dump core without dying to a signal.
C<WIFSTOPPED> status is not checked, as perl never spawns processes
with the C<WUNTRACED> option.
Signals are not supported under Win32 systems, since they don't
work at all like Unix signals. Win32 singals cause commands to
exit with a given exit value, which this modules I<does> capture.
Only 8-bit values are returned when C<run()> or C<system()>
is called with a single value under Win32. Multi-argument calls
to C<run()> and C<system()>, as well as the C<runx()> and
C<systemx()> always return the 32-bit Windows return values.
=head2 Reporting bugs
Before reporting a bug, please check to ensure you are using the
most recent version of C<IPC::System::Simple>. Your problem may
have already been fixed in a new release.
You can find the C<IPC::System::Simple> bug-tracker at
L<http://rt.cpan.org/Public/Dist/Display.html?Name=IPC-System-Simple> .
Please check to see if your bug has already been reported; if
in doubt, report yours anyway.
Submitting a patch and/or failing test case will greatly expedite
the fixing of bugs.
=head1 FEEDBACK
If you find this module useful, please consider rating it on the
CPAN Ratings service at
L<http://cpanratings.perl.org/rate/?distribution=IPC-System-Simple> .
The module author loves to hear how C<IPC::System::Simple> has made
your life better (or worse). Feedback can be sent to
E<lt>pjf@perltraining.com.auE<gt>.
=head1 SEE ALSO
L<autodie> uses C<IPC::System::Simple> to provide succeed-or-die
replacements to C<system> (and other built-ins) with lexical scope.
L<POSIX>, L<IPC::Run::Simple>, L<perlipc>, L<perlport>, L<IPC::Run>,
L<IPC::Run3>, L<Win32::Process>
=head1 AUTHOR
Paul Fenwick E<lt>pjf@cpan.orgE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright (C) 2006-2008 by Paul Fenwick
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.6.0 or,
at your option, any later version of Perl 5 you may have available.
=for Pod::Coverage WCOREDUMP
=cut
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