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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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