IPC::Run(3) User Contributed Perl Documentation IPC::Run(3) NAME IPC::Run - system() and background procs w/ piping, redirs, ptys (Unix, Win32) SYNOPSIS ## First,a command to run: my @cat = qw( cat ) ; ## Using run() instead of system(): use IPC::Run qw( run timeout(1,3x,3x cbreak) ) ; run \@cmd, \$in(1,8), \$out, \$err, timeout(1,3x,3x cbreak)( 10 ) or die "cat: $?" # Can do I/O to sub refs and filenames, too: run \@cmd, "in.txt", \&out, \&err or die "cat: $?" run \@cat, "in.txt", '>>', "out.txt", '2>>', "err.txt" ; # Redirecting using psuedo-terminals instad of pipes. run \@cat, '<pty<', \$in(1,8), '>pty>', \$out_and_err ; ## Scripting subprocesses (like Expect): use IPC::Run qw( start pump finish timeout(1,3x,3x cbreak) ) ; # Incrementally read(2,n,1 builtins) from / write(1,2) to scalars. # $in(1,8) is drained as it is fed to cat's stdin, # $out accumulates cat's stdout # $err accumulates cat's stderr # $h is for "harness". my $h = start \@cat, \$in(1,8), \$out, \$err, timeout(1,3x,3x cbreak)( 10 ) ; $in(1,8) .= "some input\n" ; pump $h until $out =~ /input\n/g ; $in(1,8) .= "some more input\n" ; pump $h until $out =~ /\G.*more input\n/ ; $in(1,8) .= "some final input\n" ; finish $h or die "cat returned $?" ; warn $err if(3,n) $err ; print $out ; ## All of cat's output # Piping between children run \@cat, '|', \@gzip ; # Multiple children simultaneously (run() blocks until all # children exit(3,n,1 builtins), use start() for background execution): run \@foo1, '&', \@foo2 ; # Calling \&set_up_child in(1,8) the child before it executes the # command (only works on systems with true fork() & exec(3,n,1 builtins)()) # exceptions thrown in(1,8) set_up_child() will be propagated back # to the parent and thrown from run(). run \@cat, \$in(1,8), \$out, init => \&set_up_child ; # Read from / write(1,2) to file(1,n) handles you open(2,3,n) and close(2,7,n) open(2,3,n) IN, '<in.txt' or die $! ; open(2,3,n) OUT, '>out.txt' or die $! ; print OUT "preamble\n" ; run \@cat, \*IN, \*OUT or die "cat returned $?" ; print OUT "postamble\n" ; close(2,7,n) IN ; close(2,7,n) OUT ; # Create pipes for you to read(2,n,1 builtins) / write(1,2) (like IPC::Open2 & 3). $h = start \@cat, '<pipe(2,8)', \*IN, '>pipe(2,8)', \*OUT, '2>pipe(2,8)', \*ERR or die "cat returned $?" ; print IN "some input\n" ; close(2,7,n) IN ; print <OUT>, <ERR> ; finish $h ; # Mixing input and output modes run \@cat, 'in.txt', \&catch_some_out, \*ERR_LOG ) ; # Other redirection constructs run \@cat, '>&', \$out_and_err ; run \@cat, '2>&1' ; run \@cat, '0<&3' ; run \@cat, '<&-' ; run \@cat, '3<', \$in3 ; run \@cat, '4>', \$out4 ; # etc. # Passing options: run \@cat, 'in.txt', debug => 1 ; # Call this system's shell, returns TRUE on 0 exit(3,n,1 builtins) code # THIS IS THE OPPOSITE SENSE OF system()'s RETURN VALUE run "cat a b c" or die "cat returned $?" ; # Launch a sub process directly, no shell. Can't do redirection # with this form, it's here to behave like system() with an # inverted result. $r = run "cat a b c" ; # Read from a file(1,n) in(1,8) to a scalar run io( "filename", 'r', \$recv ) ; run io( \*HANDLE, 'r', \$recv ) ; DESCRIPTION IPC::Run allows you run and interact with child processes using files, pipes, and pseudo-ttys. Both system()-style and scripted usages are supported and may be mixed. Likewise, functional and OO API styles are both supported and may be mixed. Various redirection operators reminiscent of those seen on common Unix and DOS command lines are provided. Before digging in(1,8) to the details a few LIMITATIONS are important enough to be mentioned right up front: Win32 Support Win32 support is working but EXPERIMENTAL, but does pass all rele- vant tests on NT 4.0. See "Win32 LIMITATIONS". pty Support If you need pty support, IPC::Run should work well enough most of the time(1,2,n), but IO::Pty is being improved, and IPC::Run will be improved to use IO::Pty's new features when it is release. The basic problem is that the pty needs to initialize itself before the parent writes to the master(5,8) pty, or the data written gets(3,n) lost. So IPC::Run does a sleep(1,3)(1) in(1,8) the parent after forking to (hope- fully) give the child a chance to run. This is a kludge that works well on non heavily loaded systems :(. ptys are not supported yet under Win32, but will be emulated... Debugging Tip You may use the environment variable "IPCRUNDEBUG" to see what's going on under the hood: $ IPCRUNDEBUG=basic myscript # prints minimal debugging $ IPCRUNDEBUG=data myscript # prints all data reads/writes $ IPCRUNDEBUG=details myscript # prints lots of low-level details $ IPCRUNDEBUG=gory myscript # (Win32 only) prints data moving through # the helper processes. We now return you to your regularly scheduled documentation. Harnesses Child processes and I/O handles are gathered in(1,8) to a harness, then started and run until the processing is finished or aborted. run() vs. start(); pump(); finish(); There are two modes you can run harnesses in: run() functions as an enhanced system(), and start()/pump()/finish() allow for background processes and scripted interactions with them. When using run(), all data to be sent to the harness is set(7,n,1 builtins) up in(1,8) advance (though one can feed subprocesses input from subroutine refs to get around this limitation). The harness is run and all output is col- lected from it, then any child processes are waited for: run \@cmd, \<<IN, \$out ; blah IN ## To precompile harnesses and run them later: my $h = harness \@cmd, \<<IN, \$out ; blah IN run $h ; The background and scripting API is provided by start(), pump(), and finish(): start() creates a harness if(3,n) need be (by calling harness()) and launches any subprocesses, pump() allows you to poll them for activity, and finish() then monitors the harnessed activities until they complete. ## Build the harness, open(2,3,n) all pipes, and launch the subprocesses my $h = start \@cat, \$in(1,8), \$out ; $in(1,8) = "first input\n" ; ## Now do I/O. start() does no I/O. pump $h while length $in(1,8) ; ## Wait for all input to go ## Now do some more I/O. $in(1,8) = "second input\n" ; pump $h until $out =~ /second input/ ; ## Clean up finish $h or die "cat returned $?" ; You can optionally compile the harness with harness() prior to start()ing or run()ing, and you may omit start() between harness() and pump(). You might want to do these things if(3,n) you compile your har- nesses ahead of time. Using regexps to match output As shown in(1,8) most of the scripting examples, the read-to-scalar facility for gathering subcommand's output is often used with regular expres- sions to detect stopping points. This is because subcommand output often arrives in(1,8) dribbles and drabs, often only a character or line at a time. This output is input for the main program and piles up in(1,8) variables like the $out and $err in(1,8) our examples. Regular expressions can be used to wait for appropriate output in(1,8) sev- eral ways. The "cat" example in(1,8) the previous section demonstrates how to pump() until some string(3,n) appears in(1,8) the output. Here's an example that uses "smb" to fetch files from a remote server: $h = harness \@smbclient, \$in(1,8), \$out ; $in(1,8) = "cd /src\n" ; $h->pump until $out =~ /^smb.*> \Z/m ; die "error(8,n) cding to /src:\n$out" if(3,n) $out =~ "ERR" ; $out = '' ; $in(1,8) = "mget *\n" ; $h->pump until $out =~ /^smb.*> \Z/m ; die "error(8,n) retrieving files:\n$out" if(3,n) $out =~ "ERR" ; $in(1,8) = "quit\n" ; $h->finish ; Notice that we carefully clear(1,3x,3x clrtobot) $out after the first command/response cycle? That's because IPC::Run does not delete $out when we continue, and we don't want to trip over the old output in(1,8) the second com- mand/response cycle. Say you want to accumulate all the output in(1,8) $out and analyze it after- wards. Perl offers incremental regular expression matching using the "m//gc" and pattern matching idiom and the "\G" assertion. IPC::Run is careful not to disturb the current "pos()" value for scalars it appends data to, so we could modify the above so as not to destroy $out by adding a couple of "/gc" modifiers. The "/g" keeps us from tripping over the previous prompt and the "/c" keeps us from resetting the prior match position if(3,n) the expected prompt doesn't materialize immediately: $h = harness \@smbclient, \$in(1,8), \$out ; $in(1,8) = "cd /src\n" ; $h->pump until $out =~ /^smb.*> \Z/mgc ; die "error(8,n) cding to /src:\n$out" if(3,n) $out =~ "ERR" ; $in(1,8) = "mget *\n" ; $h->pump until $out =~ /^smb.*> \Z/mgc ; die "error(8,n) retrieving files:\n$out" if(3,n) $out =~ "ERR" ; $in(1,8) = "quit\n" ; $h->finish ; analyze( $out ) ; When using this technique, you may want to preallocate $out to have plenty of memory or you may find that the act of growing $out each time(1,2,n) new input arrives causes an "O(length($out)^2)" slowdown as $out grows. Say we expect no more than 10,000 characters of input at the most. To preallocate memory to $out, do something like: my $out = "x" x 10_000 ; $out = "" ; "perl" will allocate at least 10,000 characters' worth of space, then mark the $out as having 0 length without freeing all that yummy RAM. Timeouts and Timers More than likely, you don't want your subprocesses to run forever, and sometimes it's nice(1,2) to know that they're going a little slowly. Time- outs throw exceptions after a some time(1,2,n) has elapsed, timers merely cause pump() to return after some time(1,2,n) has elapsed. Neither is reset(1,7,1 tput)/restarted automatically. Timeout objects are created by calling timeout(1,3x,3x cbreak)( $interval ) and passing the result to run(), start() or harness(). The timeout(1,3x,3x cbreak) period starts ticking just after all the child processes have been fork()ed or spawn()ed, and are polled for expiration in(1,8) run(), pump() and finish(). If/when they expire, an exception is thrown. This is typically useful to keep a subprocess from taking too long. If a timeout(1,3x,3x cbreak) occurs in(1,8) run(), all child processes will be terminated and all file(1,n)/pipe(2,8)/ptty descriptors opened by run() will be closed. File descriptors opened by the parent process and passed in(1,8) to run() are not closed in(1,8) this event. If a timeout(1,3x,3x cbreak) occurs in(1,8) pump(), pump_nb(), or finish(), it's up to you to decide whether to kill_kill() all the children or to implement some more graceful fallback. No I/O will be closed in(1,8) pump(), pump_nb() or finish() by such an exception (though I/O is often closed down in(1,8) those routines during the natural course of events). Often an exception is too harsh. timer( $interval ) creates timer objects that merely prevent pump() from blocking forever. This can be useful for detecting stalled I/O or printing a soothing message or "." to pacify an anxious user. Timeouts and timers can both be restarted at any time(1,2,n) using the timer's start() method (this is not the start() that launches subprocesses). To restart a timer, you need to keep a reference to the timer: ## Start with a nice(1,2) long timeout(1,3x,3x cbreak) to let smbclient connect. If ## pump or finish take too long, an exception will be thrown. my $h ; eval { $h = harness \@smbclient, \$in(1,8), \$out, \$err, ( my $t = timeout(1,3x,3x cbreak) 30 ) ; sleep(1,3) 11 ; # No effect: timer not running yet start $h ; $in(1,8) = "cd /src\n" ; pump $h until ! length $in(1,8) ; $in(1,8) = "ls\n" ; ## Now use a short timeout(1,3x,3x cbreak), since this should be faster $t->start( 5 ) ; pump $h until ! length $in(1,8) ; $t->start( 10 ) ; ## Give smbclient a little while to shut down. $h->finish ; } ; if(3,n) ( $@ ) { my $x = $@ ; ## Preserve $@ in(1,8) case another exception occurs $h->kill_kill ; ## kill(1,2,1 builtins) it gently, then brutally if(3,n) need be, or just ## brutally on Win32. die $x ; } Timeouts and timers are not checked once the subprocesses are shut down; they will not expire in(1,8) the interval between the last valid process and when IPC::Run scoops up the processes' result codes, for instance. Spawning synchronization, child exception propagation start() pauses the parent until the child executes the command or CODE reference and propagates any exceptions thrown (including exec(3,n,1 builtins)() fail- ure) back to the parent. This has several pleasant effects: any excep- tions thrown in(1,8) the child, including exec(3,n,1 builtins)() failure, come flying out of start() or run() as though they had ocurred in(1,8) the parent. This includes exceptions your code thrown from init subs. In this example: eval { run \@cmd, init => sub { die "blast it! foiled again!" } ; } ; print $@ ; the exception "blast it! foiled again" will be thrown from the child process (preventing the exec(3,n,1 builtins)()) and printed by the parent. In situations like run \@cmd1, "|", \@cmd2, "|", \@cmd3 ; @cmd1 will be initted and exec(3,n,1 builtins)()ed before @cmd2, and @cmd2 before @cmd3. This can save time(1,2,n) and prevent oddball errors emitted by later commands when earlier commands fail to execute. Note that IPC::Run doesn't start any commands unless it can find the executables refer- enced by all commands. These executables must pass both the "-f" and "-x" tests described in(1,8) perlfunc. Another nice(1,2) effect is that init() subs can take their time(1,2,n) doing things and there will be no problems caused by a parent continuing to execute before a child's init() routine is complete. Say the init() routine needs to open(2,3,n) a socket(2,7,n) or a temp file(1,n) that the parent wants to connect to; without this synchronization, the parent will need to implement a retry loop to wait for the child to run, since often, the parent gets(3,n) a lot of things done before the child's first timeslice is allocated. This is also quite necessary for pseudo-tty initialization, which needs to take place before the parent writes to the child via pty. Writes that occur before the pty is set(7,n,1 builtins) up can get lost. A final, minor, nicety is that debugging output from the child will be emitted before the parent continues on, making for much clearer debug- ging output in(1,8) complex situations. The only drawback I can conceive of is that the parent can't continue to operate while the child is being initted. If this ever becomes a problem in(1,8) the field, we can implement an option to avoid this behav- ior, but I don't expect it to. Win32: executing CODE references isn't supported on Win32, see "Win32 LIMITATIONS" for details. Syntax run(), start(), and harness() can all take a harness specification as input. A harness specification is either a single string(3,n) to be passed to the systems' shell: run "echo(1,3x,1 builtins) 'hi there'" ; or a list of commands, io operations, and/or timers/timeouts to exe- cute. Consecutive commands must be separated by a pipe(2,8) operator '|' or an '&'. External commands are passed in(1,8) as array references, and, on systems supporting fork(), Perl code may be passed in(1,8) as subs: run \@cmd ; run \@cmd1, '|', \@cmd2 ; run \@cmd1, '&', \@cmd2 ; run \&sub1 ; run \&sub1, '|', \&sub2 ; run \&sub1, '&', \&sub2 ; '|' pipes the stdout of \@cmd1 the stdin of \@cmd2, just like a shell pipe. '&' does not. Child processes to the right of a '&' will have their stdin closed unless it's redirected-to. IPC::Run::IO objects may be passed in(1,8) as well, whether or not child processes are also specified: run io( "infile", ">", \$in(1,8) ), io( "outfile", "<", \$in(1,8) ) ; as can IPC::Run::Timer objects: run \@cmd, io( "outfile", "<", \$in(1,8) ), timeout(1,3x,3x cbreak)( 10 ) ; Commands may be followed by scalar, sub, or i/o handle references for redirecting child process input & output: run \@cmd, \undef, \$out ; run \@cmd, \$in(1,8), \$out ; run \@cmd1, \&in(1,8), '|', \@cmd2, \*OUT ; run \@cmd1, \*IN, '|', \@cmd2, \&out ; This is known as succinct redirection syntax, since run(), start() and harness(), figure out which file(1,n) descriptor to redirect and how. File descriptor 0 is presumed to be an input for the child process, all oth- ers are outputs. The assumed file(1,n) descriptor always starts at 0, unless the command is being piped to, in(1,8) which case it starts at 1. To be explicit about your redirects, or if(3,n) you need to do more complex things, there's also a redirection operator syntax: run \@cmd, '<', \undef, '>', \$out ; run \@cmd, '<', \undef, '>&', \$out_and_err ; run( \@cmd1, '<', \$in(1,8), '|', \@cmd2, \$out ) ; Operator syntax is required if(3,n) you need to do something other than sim- ple redirection to/from scalars or subs, like duping or closing file(1,n) descriptors or redirecting to/from a named(5,8) file. The operators are covered in(1,8) detail below. After each \@cmd (or \&foo), parsing begins in(1,8) succinct mode and tog- gles to operator syntax mode when an operator (ie plain scalar, not a ref) is seen. Once in(1,8) operator syntax mode, parsing only reverts to succinct mode when a '|' or '&' is seen. In succinct mode, each parameter after the \@cmd specifies what to do with the next highest file(1,n) descriptor. These File descriptor start with 0 (stdin) unless stdin is being piped to ("'|', \@cmd"), in(1,8) which case they start with 1 (stdout). Currently, being on the left of a pipe(2,8) ("\@cmd, \$out, \$err, '|'") does not cause stdout to be skipped, though this may change since it's not as DWIMerly as it could be. Only stdin is assumed to be an input in(1,8) succinct mode, all others are assumed to be outputs. If no piping or redirection is specified for a child, it will inherit the parent's open(2,3,n) file(1,n) handles as dictated by your system's close-on- exec(3,n,1 builtins) behavior and the $^F flag, except that processes after a '&' will not inherit the parent's stdin. Also note that $^F does not affect file(1,n) desciptors obtained via POSIX, since it only applies to full-fledged Perl file(1,n) handles. Such processes will have their stdin closed unless it has been redirected-to. If you want to close(2,7,n) a child processes stdin, you may do any of: run \@cmd, \undef ; run \@cmd, \"" ; run \@cmd, '<&-' ; run \@cmd, '0<&-' ; Redirection is done by placing redirection specifications immediately after a command or child subroutine: run \@cmd1, \$in(1,8), '|', \@cmd2, \$out ; run \@cmd1, '<', \$in(1,8), '|', \@cmd2, '>', \$out ; If you omit the redirection operators, descriptors are counted starting at 0. Descriptor 0 is assumed to be input, all others are outputs. A leading '|' consumes descriptor 0, so this works as expected. run \@cmd1, \$in(1,8), '|', \@cmd2, \$out ; The parameter following a redirection operator can be a scalar ref, a subroutine ref, a file(1,n) name, an open(2,3,n) filehandle, or a closed filehan- dle. If it's a scalar ref, the child reads input from or sends output to that variable: $in(1,8) = "Hello World.\n" ; run \@cat, \$in(1,8), \$out ; print $out ; Scalars used in(1,8) incremental (start()/pump()/finish()) applications are treated as queues: input is removed from input scalers, resulting in(1,8) them dwindling to '', and output is appended to output scalars. This is not true of harnesses run() in(1,8) batch mode. It's usually wise to append new input to be sent to the child to the input queue(1,3), and you'll often want to zap output queues to '' before pumping. $h = start \@cat, \$in(1,8) ; $in(1,8) = "line 1\n" ; pump $h ; $in(1,8) .= "line 2\n" ; pump $h ; $in(1,8) .= "line 3\n" ; finish $h ; The final call to finish() must be there: it allows the child process(es) to run to completion and waits for their exit(3,n,1 builtins) values. OBSTINATE CHILDREN Interactive applications are usually optimized for human use. This can help or hinder trying to interact with them through modules like IPC::Run. Frequently, programs alter their behavior when they detect that stdin, stdout, or stderr are not connected to a tty(1,4), assuming that they are being run in(1,8) batch mode. Whether this helps or hurts depends on which optimizations change. And there's often no way of telling what a program does in(1,8) these areas other than trial and error(8,n) and, occasionally, reading the source. This includes different versions and implementations of the same program. All hope is not lost, however. Most programs behave in(1,8) reasonably tractable manners, once you figure out what it's trying to do. Here are some of the issues you might need to be aware of. fflush()ing stdout and stderr This lets the user see stdout and stderr immediately. Many pro- grams undo this optimization if(3,n) stdout is not a tty(1,4), making them harder to manage by things like IPC::Run. Many programs decline to fflush stdout or stderr if(3,n) they do not detect a tty(1,4) there. Some ftp commands do this, for instance. If this happens to you, look(1,8,3 Search::Dict) for a way to force interactive behav- ior, like a command line switch(1,n) or command. If you can't, you will need to use a pseudo terminal ('<pty<' and '>pty>'). false prompts Interactive programs generally do not guarantee that output from user commands won't contain a prompt string. For example, your shell prompt might be a '$', and a file(1,n) named(5,8) '$' might be the only file(1,n) in(1,8) a directory listing. This can make it hard to guarantee that your output parser won't be fooled into early termination of results. To help work around this, you can see if(3,n) the program can alter it's prompt, and use something you feel is never going to occur in(1,8) actual practice. You should also look(1,8,3 Search::Dict) for your prompt to be the only thing on a line: pump $h until $out =~ /^<SILLYPROMPT>\s?\z/m ; (use "(?!\n)\Z" in(1,8) place of "\z" on older perls). You can also take the approach that IPC::ChildSafe takes and emit a command with known output after each 'real' command you issue, then look(1,8,3 Search::Dict) for this known output. See new_appender() and new_chunker() for filters that can help with this task. If it's not convenient or possibly to alter a prompt or use a known command/response pair, you might need to autodetect the prompt in(1,8) case the local version(1,3,5) of the child program is different then the one you tested with, or if(3,n) the user has control over the look(1,8,3 Search::Dict) & feel of the prompt. Refusing to accept(2,8) input unless stdin is a tty. Some programs, for security reasons, will only accept(2,8) certain types of input from a tty. su, notable, will not prompt for a password unless it's connected to a tty. If this is your situation, use a pseudo terminal ('<pty<' and '>pty>'). Not prompting unless connected to a tty. Some programs don't prompt unless stdin or stdout is a tty. See if(3,n) you can turn prompting back on. If not, see if(3,n) you can come up with a command that you can issue after every real command and look(1,8,3 Search::Dict) for it's output, as IPC::ChildSafe does. There are two filters included with IPC::Run that can help with doing this: appender and chunker (see new_appender() and new_chunker()). Different output format when not connected to a tty. Some commands alter their formats to ease machine parsability when they aren't connected to a pipe. This is actually good, but can be surprising. PSEUDO TERMINALS On systems providing pseudo terminals under /dev, IPC::Run can use IO::Pty (available on CPAN) to provide a terminal environment to sub- processes. This is necessary when the subprocess really wants to think it's connected to a real terminal. CAVEATS Psuedo-terminals are not pipes, though they are similar. Here are some differences to watch out for. Echoing Sending to stdin will cause an echo(1,3x,1 builtins) on stdout, which occurs before each line is passed to the child program. There is currently no way to disable this, although the child process can and should dis- able it for things like passwords. Shutdown IPC::Run cannot close(2,7,n) a pty until all output has been collected. This means that it is not possible to send(2,n) an EOF to stdin by half- closing the pty, as we can when using a pipe(2,8) to stdin. This means that you need to send(2,n) the child process an exit(3,n,1 builtins) command or signal(2,7), or run() / finish() will time(1,2,n) out. Be careful not to expect a prompt after sending the exit(3,n,1 builtins) command. Command line editing Some subprocesses, notable shells that depend on the user's prompt settings, will reissue the prompt plus the command line input so far once for each character. '>pty>' means '&>pty>', not '1>pty>' The pseudo terminal redirects both stdout and stderr unless you specify a file(1,n) descriptor. If you want to grab stderr separately, do this: start \@cmd, '<pty<', \$in(1,8), '>pty>', \$out, '2>', \$err ; stdin, stdout, and stderr not inherited Child processes harnessed to a pseudo terminal have their stdin, stdout, and stderr completely closed before any redirection opera- tors take effect. This casts of the bonds of the controlling ter- minal. This is not done when using pipes. Right now, this affects all children in(1,8) a harness that has a pty in(1,8) use, even if(3,n) that pty would not affect a particular child. That's a bug and will be fixed. Until it is, it's best not to mix-and- match children. Redirection Operators Operator SHNP Description ======== ==== =========== <, N< SHN Redirects input to a child's fd N (0 assumed) >, N> SHN Redirects output from a child's fd N (1 assumed) >>, N>> SHN Like '>', but appends to scalars or named(5,8) files >&, &> SHN Redirects stdout & stderr from a child process <pty, N<pty S Like '<', but uses a pseudo-tty instead of a pipe(2,8) >pty, N>pty S Like '>', but uses a pseudo-tty instead of a pipe(2,8) N<&M Dups input fd N to input fd M M>&N Dups output fd N to input fd M N<&- Closes fd N <pipe(2,8), N<pipe(2,8) P Pipe opens H for caller to read(2,n,1 builtins), write(1,2), close. >pipe(2,8), N>pipe(2,8) P Pipe opens H for caller to read(2,n,1 builtins), write(1,2), close. 'N' and 'M' are placeholders for integer file(1,n) descriptor numbers. The terms 'input' and 'output' are from the child process's perspective. The SHNP field indicates what parameters an operator can take: S: \$scalar or \&function references. Filters may be used with these operators (and only these). H: \*HANDLE or IO::Handle for caller to open(2,3,n), and close(2,7,n) N: "file(1,n) name". P: \*HANDLE opened by IPC::Run as the parent end of a pipe(2,8), but read(2,n,1 builtins) and written to and closed by the caller (like IPC::Open3). Redirecting input: [n]<, [n]<pipe(2,8) You can input the child reads on file(1,n) descriptor number n to come from a scalar variable, subroutine, file(1,n) handle, or a named(5,8) file. If stdin is not redirected, the parent's stdin is inherited. run \@cat, \undef ## Closes child's stdin immediately or die "cat returned $?" ; run \@cat, \$in(1,8) ; run \@cat, \<<TOHERE ; blah TOHERE run \@cat, \&input ; ## Calls &input, feeding data returned ## to child's. Closes child's stdin ## when undef is returned. Redirecting from named(5,8) files requires you to use the input redi- rection operator: run \@cat, '<.profile' ; run \@cat, '<', '.profile' ; open(2,3,n) IN, "<foo" ; run \@cat, \*IN ; run \@cat, *IN{IO} ; The form used second example here is the safest, since filenames like "0" and "&more\n" won't confuse &run: You can't do either of run \@a, *IN ; ## INVALID run \@a, '<', *IN ; ## BUGGY: Reads file(1,n) named(5,8) like "*main::A" because perl passes a scalar containing a string(3,n) that looks like "*main::A" to &run, and &run can't tell the difference between that and a redirection operator or a file(1,n) name. &run guarantees that any scalar you pass after a redirection operator is a file(1,n) name. If your child process will take input from file(1,n) descriptors other than 0 (stdin), you can use a redirection operator with any of the valid input forms (scalar ref, sub ref, etc.): run \@cat, '3<', \$in3 ; When redirecting input from a scalar ref, the scalar ref is used as a queue. This allows you to use &harness and pump() to feed incre- mental bits of input to a coprocess. See "Coprocesses" below for more information. The <pipe(2,8) operator opens the write(1,2) half of a pipe(2,8) on the filehandle glob(1,3,7,n) reference it takes as an argument: $h = start \@cat, '<pipe(2,8)', \*IN ; print IN "hello world\n" ; pump $h ; close(2,7,n) IN ; finish $h ; Unlike the other '<' operators, IPC::Run does nothing further with it: you are responsible for it. The previous example is function- ally equivalent to: pipe(2,8)( \*R, \*IN ) or die $! ; $h = start \@cat, '<', \*IN ; print IN "hello world\n" ; pump $h ; close(2,7,n) IN ; finish $h ; This is like the behavior of IPC::Open2 and IPC::Open3. Win32: The handle returned is actually a socket(2,7,n) handle, so you can use select(2,7,2 select_tut)() on it. Redirecting output: [n]>, [n]>>, [n]>&[m], [n]>pipe(2,8) You can redirect any output the child emits to a scalar variable, subroutine, file(1,n) handle, or file(1,n) name. You can have &run truncate(2,7) or append to named(5,8) files or scalars. If you are redirecting stdin as well, or if(3,n) the command is on the receiving end of a pipeline ('|'), you can omit the redirection operator: @ls = ( 'ls' ) ; run \@ls, \undef, \$out or die "ls returned $?" ; run \@ls, \undef, \&out ; ## Calls &out each time(1,2,n) some output ## is received from the child's ## when undef is returned. run \@ls, \undef, '2>ls.err' ; run \@ls, '2>', 'ls.err' ; The two parameter form guarantees that the filename will not be interpreted as a redirection operator: run \@ls, '>', "&more" ; run \@ls, '2>', ">foo\n" ; You can pass file(1,n) handles you've opened for writing: open(2,3,n)( *OUT, ">out.txt" ) ; open(2,3,n)( *ERR, ">err.txt" ) ; run \@cat, \*OUT, \*ERR ; Passing a scalar reference and a code reference requires a little more work, but allows you to capture all of the output in(1,8) a scalar or each piece of output by a callback: These two do the same things: run( [ 'ls' ], '2>', sub { $err_out .= $_[0] } ) ; does the same basic thing as: run( [ 'ls' ], '2>', \$err_out ) ; The subroutine will be called each time(1,2,n) some data is read(2,n,1 builtins) from the child. The >pipe(2,8) operator is different in(1,8) concept than the other '>' oper- ators, although it's syntax is similar: $h = start \@cat, $in(1,8), '>pipe(2,8)', \*OUT, '2>pipe(2,8)', \*ERR ; $in(1,8) = "hello world\n" ; finish $h ; print <OUT> ; print <ERR> ; close(2,7,n) OUT ; close(2,7,n) ERR ; causes two pipe(2,8) to be created, with one end attached to cat's std- out and stderr, respectively, and the other left open(2,3,n) on OUT and ERR, so that the script can manually read(2,n,1 builtins)(), select(2,7,2 select_tut)(), etc. on them. This is like the behavior of IPC::Open2 and IPC::Open3. Win32: The handle returned is actually a socket(2,7,n) handle, so you can use select(2,7,2 select_tut)() on it. Duplicating output descriptors: >&m, n>&m This duplicates output descriptor number n (default is 1 if(3,n) n is omitted) from descriptor number m. Duplicating input descriptors: <&m, n<&m This duplicates input descriptor number n (default is 0 if(3,n) n is omitted) from descriptor number m Closing descriptors: <&-, 3<&- This closes descriptor number n (default is 0 if(3,n) n is omitted). The following commands are equivalent: run \@cmd, \undef ; run \@cmd, '<&-' ; run \@cmd, '<in.txt', '<&-' ; Doing run \@cmd, \$in(1,8), '<&-' ; ## SIGPIPE recipe. is dangerous: the parent will get a SIGPIPE if(3,n) $in(1,8) is not empty. Redirecting both stdout and stderr: &>, >&, &>pipe(2,8), >pipe(2,8)& The following pairs of commands are equivalent: run \@cmd, '>&', \$out ; run \@cmd, '>', \$out, '2>&1' ; run \@cmd, '>&', 'out.txt' ; run \@cmd, '>', 'out.txt', '2>&1' ; etc. File descriptor numbers are not permitted to the left or the right of these operators, and the '&' may occur on either end of the operator. The '&>pipe(2,8)' and '>pipe(2,8)&' variants behave like the '>pipe(2,8)' opera- tor, except that both stdout and stderr write(1,2) to the created pipe. Redirection Filters Both input redirections and output redirections that use scalars or subs as endpoints may have an arbitrary number of filter(1,3x,3x curs_util) subs placed between them and the child process. This is useful if(3,n) you want to receive output in(1,8) chunks, or if(3,n) you want to massage each chunk of data sent to the child. To use this feature, you must use operator syntax: run( \@cmd '<', \&in_filter_2, \&in_filter_1, $in(1,8), '>', \&out_filter_1, \&in_filter_2, $out, ) ; This capability is not provided for IO handles or named(5,8) files. Two filters are provided by IPC::Run: appender and chunker. Because these may take an argument, you need to use the constructor functions new_appender() and new_chunker() rather than using \& syntax: run( \@cmd '<', new_appender( "\n" ), $in(1,8), '>', new_chunker, $out, ) ; Just doing I/O If you just want to do I/O to a handle or file(1,n) you open(2,3,n) yourself, you may specify a filehandle or filename instead of a command in(1,8) the har- ness specification: run io( "filename", '>', \$recv ) ; $h = start io( $io, '>', \$recv ) ; $h = harness \@cmd, '&', io( "file(1,n)", '<', \$send(2,n) ) ; Options Options are passed in(1,8) as name/value pairs: run \@cat, \$in(1,8), debug => 1 ; If you pass the debug option, you may want to pass it in(1,8) first, so you can see what parsing is going on: run debug => 1, \@cat, \$in(1,8) ; debug Enables debugging output in(1,8) parent and child. Debugging info(1,5,n) is emitted to the STDERR that was present when IPC::Run was first "use()"ed (it's "dup()"ed out of the way so that it can be redi- rected in(1,8) children without having debugging output emitted on it). RETURN VALUES harness() and start() return a reference to an IPC::Run harness. This is blessed in(1,8) to the IPC::Run package, so you may make later calls to functions as members if(3,n) you like: $h = harness( ... ) ; $h->start ; $h->pump ; $h->finish ; $h = start( .... ) ; $h->pump ; ... Of course, using method call syntax lets you deal with any IPC::Run subclasses that might crop up, but don't hold your breath waiting for any. run() and finish() return TRUE when all subcommands exit(3,n,1 builtins) with a 0 result code. This is the opposite of perl's system() command. All routines raise(3,n) exceptions (via die()) when error(8,n) conditions are recognized. A non-zero command result is not treated as an error(8,n) con- dition, since some commands are tests whose results are reported in(1,8) their exit(3,n,1 builtins) codes. ROUTINES run Run takes a harness or harness specification and runs it, pumping all input to the child(ren), closing the input pipes when no more input is available, collecting all output that arrives, until the pipes delivering output are closed, then waiting for the children to exit(3,n,1 builtins) and reaping their result codes. You may think of "run( ... )" as being like start( ... )->finish() ; , though there is one subtle difference: run() does not set(7,n,1 builtins) \$input_scalars to '' like finish() does. If an exception is thrown from run(), all children will be killed off "gently", and then "annihilated" if(3,n) they do not go gently (in(1,8) to that dark night. sorry). If any exceptions are thrown, this does a "kill_kill" before pro- pogating them. signal(2,7) ## To send(2,n) it a specific signal(2,7) by name ("USR1"): signal(2,7) $h, "USR1" ; $h->signal(2,7) ( "USR1" ) ; If $signal(2,7) is provided and defined, sends a signal(2,7) to all child processes. Try not to send(2,n) numeric signals, use "KILL" instead of 9, for instance. Numeric signals aren't portable. Throws an exception if(3,n) $signal(2,7) is undef. This will not clean up the harness, "finish" it if(3,n) you kill(1,2,1 builtins) it. Normally TERM kills a process gracefully (this is what the command line utility "kill(1,2,1 builtins)" does by default), INT is sent by one of the keys "^C", "Backspace" or "<Del>", and "QUIT" is used to kill(1,2,1 builtins) a process and make it coredump. The "HUP" signal(2,7) is often used to get a process to "restart", rereading config(1,5) files, and "USR1" and "USR2" for really applica- tion-specific things. Often, running "kill(1,2,1 builtins) -l" (that's a lower case "L") on the command line will list the signals present on your operating system. WARNING: The signal(2,7) subsystem is not at all portable. We *may* offer to simulate "TERM" and "KILL" on some operating systems, sub- mit code to me if(3,n) you want this. WARNING 2: Up to and including perl v5.6.1, doing almost anything in(1,8) a signal(2,7) handler could be dangerous. The most safe code avoids all mallocs and system calls, usually by preallocating a flag before entering the signal(2,7) handler, altering the flag's value in(1,8) the handler, and responding to the changed value in(1,8) the main sys- tem: my $got_usr1 = 0 ; sub usr1_handler { ++$got_signal } $SIG{USR1} = \&usr1_handler ; while () { sleep(1,3) 1 ; print "GOT IT" while $got_usr1-- ; } Even this approach is perilous if(3,n) ++ and -- aren't atomic on your system (I've never heard of this on any modern CPU large enough to run perl). kill_kill ## To kill(1,2,1 builtins) off a process: $h->kill_kill ; kill_kill $h ; ## To specify the grace period other than 30 seconds: kill_kill $h, grace => 5 ; ## To send(2,n) QUIT instead of KILL if(3,n) a process refuses to die: kill_kill $h, coup_d_grace => "QUIT" ; Sends a "TERM", waits for all children to exit(3,n,1 builtins) for up to 30 sec- onds, then sends a "KILL" to any that survived the "TERM". Will wait for up to 30 more seconds for the OS to sucessfully "KILL" the processes. The 30 seconds may be overriden by setting the "grace" option, this overrides both timers. The harness is then cleaned up. The doubled name indicates that this function may kill(1,2,1 builtins) again and avoids colliding with the core Perl "kill(1,2,1 builtins)" function. Returns a 1 if(3,n) the "TERM" was sufficient, or a 0 if(3,n) "KILL" was required. Throws an exception if(3,n) "KILL" did not permit the chil- dren to be reaped. NOTE: The grace period is actually up to 1 second longer than that given. This is because the granularity of "time(1,2,n)" is 1 second. Let me know if(3,n) you need finer granularity, we can leverage Time::HiRes here. Win32: Win32 does not know how to send(2,n) real signals, so "TERM" is a full-force kill(1,2,1 builtins) on Win32. Thus all talk of grace periods, etc. do not apply to Win32. harness Takes a harness specification and returns a harness. This harness is blessed in(1,8) to IPC::Run, allowing you to use method call syntax for run(), start(), et al if(3,n) you like. harness() is provided so that you can pre-build harnesses if(3,n) you would like to, but it's not required.. You may proceed to run(), start() or pump() after calling harness() (pump() calls start() if(3,n) need be). Alternatively, you may pass your harness specification to run() or start() and let them har- ness() for you. You can't pass harness specifications to pump(), though. close_terminal This is used as (or in(1,8)) an init sub to cast off the bonds of a con- trolling terminal. It must precede all other redirection ops that affect STDIN, STDOUT, or STDERR to be guaranteed effective. start $h = start( \@cmd, \$in(1,8), \$out, ..., timeout(1,3x,3x cbreak)( 30, name => "process timeout(1,3x,3x cbreak)" ), $stall_timeout = timeout(1,3x,3x cbreak)( 10, name => "stall timeout(1,3x,3x cbreak)" ), ) ; $h = start \@cmd, '<', \$in(1,8), '|', \@cmd2, ... ; start() accepts a harness or harness specification and returns a harness after building all of the pipes and launching (via fork()/exec(3,n,1 builtins)(), or, maybe someday, spawn()) all the child processes. It does not send(2,n) or receive any data on the pipes, see pump() and finish() for that. You may call harness() and then pass it's result to start() if(3,n) you like, but you only need to if(3,n) it helps you structure or tune your application. If you do call harness(), you may skip start() and proceed directly to pump. start() also starts all timers in(1,8) the harness. See IPC::Run::Timer for more information. start() flushes STDOUT and STDERR to help you avoid duplicate out- put. It has no way of asking Perl to flush(8,n) all your open(2,3,n) filehan- dles, so you are going to need to flush(8,n) any others you have open. Sorry. Here's how if(3,n) you don't want to alter the state of $| for your filehandle: $ofh = select(2,7,2 select_tut) HANDLE ; $of = $| ; $| = 1 ; $| = $of ; select(2,7,2 select_tut) $ofh; If you don't mind leaving output unbuffered on HANDLE, you can do the slightly shorter $ofh = select(2,7,2 select_tut) HANDLE ; $| = 1 ; select(2,7,2 select_tut) $ofh; Or, you can use IO::Handle's flush(8,n)() method: use IO::Handle ; flush(8,n) HANDLE ; Perl needs the equivalent of C's fflush( (FILE *)NULL ). pump pump $h ; $h->pump ; Pump accepts a single parameter harness. It blocks until it deliv- ers some input or recieves some output. It returns TRUE if(3,n) there is still input or output to be done, FALSE otherwise. pump() will automatically call start() if(3,n) need be, so you may call harness() then proceed to pump() if(3,n) that helps you structure your application. If pump() is called after all harnessed activities have completed, a "process ended prematurely" exception to be thrown. This allows for simple scripting of external applications without having to add lots of error(8,n) handling code at each step of the script: $h = harness \@smbclient, \$in(1,8), \$out, $err ; $in(1,8) = "cd /foo\n" ; $h->pump until $out =~ /^smb.*> \Z/m ; die "error(8,n) cding to /foo:\n$out" if(3,n) $out =~ "ERR" ; $out = '' ; $in(1,8) = "mget *\n" ; $h->pump until $out =~ /^smb.*> \Z/m ; die "error(8,n) retrieving files:\n$out" if(3,n) $out =~ "ERR" ; $h->finish ; warn $err if(3,n) $err ; pump_nb pump_nb $h ; $h->pump_nb ; "pump() non-blocking", pumps if(3,n) anything's ready to be pumped, returns immediately otherwise. This is useful if(3,n) you're doing some long-running task in(1,8) the foreground, but don't want to starve any child processes. pumpable Returns TRUE if(3,n) calling pump() won't throw an immediate "process ended prematurely" exception. This means that there are open(2,3,n) I/O channels or active processes. May yield the parent processes' time(1,2,n) slice for 0.01 second if(3,n) all pipes are to the child and all are paused. In this case we can't tell if(3,n) the child is dead, so we yield the processor and then attempt to reap the child in(1,8) a non- blocking way. reap_nb Attempts to reap child processes, but does not block. Does not currently take any parameters, one day it will allow spe- cific children to be reaped. Only call this from a signal(2,7) handler if(3,n) your "perl" is recent enough to have safe signal(2,7) handling (5.6.1 did not, IIRC, but it was beign discussed on perl5-porters). Calling this (or doing any significant work) in(1,8) a signal(2,7) handler on older "perl"s is asking for seg faults. finish This must be called after the last start() or pump() call for a harness, or your system will accumulate defunct processes and you may "leak" file(1,n) descriptors. finish() returns TRUE if(3,n) all children returned 0 (and were not sig- naled and did not coredump, ie ! $?), and FALSE otherwise (this is like run(), and the opposite of system()). Once a harness has been finished, it may be run() or start()ed again, including by pump()s auto-start. If this throws an exception rather than a normal exit(3,n,1 builtins), the harness may be left in(1,8) an unstable state, it's best to kill(1,2,1 builtins) the harness to get rid of all the child processes, etc. Specifically, if(3,n) a timeout(1,3x,3x cbreak) expires in(1,8) finish(), finish() will not kill(1,2,1 builtins) all the children. Call "<$h-"kill_kill>> in(1,8) this case if(3,n) you care. This differs from the behavior of "run". result $h->result ; Returns the first non-zero result code (ie $? >> 8). See "full_result" to get the $? value for a child process. To get the result of a particular child, do: $h->result( 0 ) ; # first child's $? >> 8 $h->result( 1 ) ; # second child or ($h->results)[0] ($h->results)[1] Returns undef if(3,n) no child processes were spawned and no child num- ber was specified. Throws an exception if(3,n) an out-of-range child number is passed. results Returns a list of child exit(3,n,1 builtins) values. See "full_results" if(3,n) you want to know if(3,n) a signal(2,7) killed the child. Throws an exception if(3,n) the harness is not in(1,8) a finished state. full_result $h->full_result ; Returns the first non-zero $?. See "result" to get the first $? >> 8 value for a child process. To get the result of a particular child, do: $h->full_result( 0 ) ; # first child's $? >> 8 $h->full_result( 1 ) ; # second child or ($h->full_results)[0] ($h->full_results)[1] Returns undef if(3,n) no child processes were spawned and no child num- ber was specified. Throws an exception if(3,n) an out-of-range child number is passed. full_results Returns a list of child exit(3,n,1 builtins) values as returned by "wait". See "results" if(3,n) you don't care about coredumps or signals. Throws an exception if(3,n) the harness is not in(1,8) a finished state. FILTERS These filters are used to modify input our output between a child process and a scalar or subroutine endpoint. binary run \@cmd, ">", binary, \$out ; run \@cmd, ">", binary, \$out ; ## Any TRUE value to enable run \@cmd, ">", binary 0, \$out ; ## Any FALSE value to disable This is a constructor for a "binmode" "filter(1,3x,3x curs_util)" that tells IPC::Run to keep the carriage returns that would ordinarily be edited out for you (binmode is usually off). This is not a real filter(1,3x,3x curs_util), but an option masquerading as a filter. It's not named(5,8) "binmode" because you're likely to want to call Perl's binmode in(1,8) programs that are piping binary data around. new_chunker This breaks a stream of data in(1,8) to chunks, based on an optional scalar or regular expression parameter. The default is the Perl input record separator in(1,8) $/, which is a newline be default. run \@cmd, '>', new_chunker, \&lines_handler ; run \@cmd, '>', new_chunker( "\r\n" ), \&lines_handler ; Because this uses $/ by default, you should always pass in(1,8) a param- eter if(3,n) you are worried about other code (modules, etc) modifying $/. If this filter(1,3x,3x curs_util) is last in(1,8) a filter(1,3x,3x curs_util) chain that dumps in(1,8) to a scalar, the scalar must be set(7,n,1 builtins) to '' before a new chunk will be written to it. As an example of how a filter(1,3x,3x curs_util) like this can be written, here's a chunker that splits on newlines: sub line_splitter { my ( $in_ref, $out_ref ) = @_ ; return 0 if(3,n) length $$out_ref ; return input_avail && do { while (1) { if(3,n) ( $$in_ref =~ s/\A(.*?\n)// ) { $$out_ref .= $1 ; return 1 ; } my $hmm = get_more_input ; unless ( defined $hmm ) { $$out_ref = $$in_ref ; $$in_ref = '' ; return length $$out_ref ? 1 : 0 ; } return 0 if(3,n) $hmm eq 0 ; } } } ; new_appender This appends a fixed string(3,n) to each chunk of data read(2,n,1 builtins) from the source scalar or sub. This might be useful if(3,n) you're writing com- mands to a child process that always must end in(1,8) a fixed string(3,n), like "\n": run( \@cmd, '<', new_appender( "\n" ), \&commands, ) ; Here's a typical filter(1,3x,3x curs_util) sub that might be created by new_appen- der(): sub newline_appender { my ( $in_ref, $out_ref ) = @_ ; return input_avail && do { $$out_ref = join(1,n)( '', $$out_ref, $$in_ref, "\n" ) ; $$in_ref = '' ; 1 ; } } ; io Takes a filename or filehandle, a redirection operator, optional filters, and a source or destination (depends on the redirection operator). Returns an IPC::Run::IO object suitable for har- ness()ing (including via start() or run()). This is shorthand for require IPC::Run::IO ; ... IPC::Run::IO->new(...) ... timer $h = start( \@cmd, \$in(1,8), \$out, $t = timer( 5 ) ) ; pump $h until $out =~ /expected stuff/ || $t->is_expired ; Instantiates a non-fatal timer. pump() returns once each time(1,2,n) a timer expires. Has no direct effect on run(), but you can pass a subroutine to fire when the timer expires. See "timeout(1,3x,3x cbreak)" for building timers that throw exceptions on expira- tion. See "timer" in(1,8) IPC::Run::Timer for details. timeout(1,3x,3x cbreak) $h = start( \@cmd, \$in(1,8), \$out, $t = timeout(1,3x,3x cbreak)( 5 ) ) ; pump $h until $out =~ /expected stuff/ ; Instantiates a timer that throws an exception when it expires. If you don't provide an exception, a default exception that matches /^IPC::Run: .*timed out/ is thrown by default. You can pass in(1,8) your own exception scalar or reference: $h = start( \@cmd, \$in(1,8), \$out, $t = timeout(1,3x,3x cbreak)( 5, exception => 'slowpoke' ), ) ; or set(7,n,1 builtins) the name used in(1,8) debugging message and in(1,8) the default excep- tion string: $h = start( \@cmd, \$in(1,8), \$out, timeout(1,3x,3x cbreak)( 50, name => 'process timer' ), $stall_timer = timeout(1,3x,3x cbreak)( 5, name => 'stall timer' ), ) ; pump $h until $out =~ /started/ ; $in(1,8) = 'command 1' ; $stall_timer->start ; pump $h until $out =~ /command 1 finished/ ; $in(1,8) = 'command 2' ; $stall_timer->start ; pump $h until $out =~ /command 2 finished/ ; $in(1,8) = 'very slow command 3' ; $stall_timer->start( 10 ) ; pump $h until $out =~ /command 3 finished/ ; $stall_timer->start( 5 ) ; $in(1,8) = 'command 4' ; pump $h until $out =~ /command 4 finished/ ; $stall_timer->reset(1,7,1 tput); # Prevent restarting or expirng finish $h ; See "timer" for building non-fatal timers. See "timer" in(1,8) IPC::Run::Timer for details. FILTER IMPLEMENTATION FUNCTIONS These functions are for use from within filters. input_avail Returns TRUE if(3,n) input is available. If none is available, then &get_more_input is called and its result is returned. This is usually used in(1,8) preference to &get_more_input so that the calling filter(1,3x,3x curs_util) removes all data from the $in_ref before more data gets(3,n) read(2,n,1 builtins) in(1,8) to $in_ref. "input_avail" is usually used as part of a return expression: return input_avail && do { ## process the input just gotten 1 ; } ; This technique allows input_avail to return the undef or 0 that a filter(1,3x,3x curs_util) normally returns when there's no input to process. If a filter(1,3x,3x curs_util) stores intermediate values, however, it will need to react to an undef: my $got = input_avail ; if(3,n) ( ! defined $got ) { ## No more input ever, flush(8,n) internal buffers to $out_ref } return $got unless $got ; ## Got some input, move(3x,7,3x curs_move) as much as need be return 1 if(3,n) $added_to_out_ref ; get_more_input This is used to fetch more input in(1,8) to the input variable. It returns undef if(3,n) there will never be any more input, 0 if(3,n) there is none now, but there might be in(1,8) the future, and TRUE if(3,n) more input was gotten. "get_more_input" is usually used as part of a return expression, see "input_avail" for more information. TODO These will be addressed as needed and as time(1,2,n) allows. Stall timeout. Expose a list of child process objects. When I do this, each child process is likely to be blessed into IPC::Run::Proc. $kid->abort(3,7)(), $kid->kill(1,2,1 builtins)(), $kid->signal(2,7)( $num_or_name ). Write tests for /(full_)?results?/ subs. Currently, pump() and run() only work on systems where select(2,7,2 select_tut)() works on the filehandles returned by pipe(2,8)(). This does *not* include ActiveState on Win32, although it does work on cygwin under Win32 (thought the tests whine a bit). I'd like to rectify that, suggestions and patches welcome. Likewise start() only fully works on fork()/exec(3,n,1 builtins)() machines (well, just fork() if(3,n) you only ever pass perl subs as subprocesses). There's some scaffolding for calling Open3::spawn_with_handles(), but that's untested, and not that useful with limited select(2,7,2 select_tut)(). Support for "\@sub_cmd" as an argument to a command which gets(3,n) replaced with /dev/fd or the name of a temporary file(1,n) containing foo's output. This is like <(sub_cmd ...) found in(1,8) bash and csh (IIRC). Allow multiple harnesses to be combined as independant sets of pro- cesses in(1,8) to one 'meta-harness'. Allow a harness to be passed in(1,8) place of an \@cmd. This would allow multiple harnesses to be aggregated. Ability to add external file(1,n) descriptors w/ filter(1,3x,3x curs_util) chains and end- points. Ability to add timeouts and timing generators (i.e. repeating time- outs). High resolution timeouts. Win32 LIMITATIONS Fails on Win9X If you want Win9X support, you'll have to debug it or fund me because I don't use that system any more. The Win32 subsysem has been extended to use temporary files in(1,8) simple run() invocations and these may actually work on Win9X too, but I don't have time(1,2,n) to work on it. May deadlock on Win2K (but not WinNT4 or WinXPPro) Spawning more than one subprocess on Win2K causes a deadlock I haven't figured out yet, but simple uses of run() often work. Passes all tests on WinXPPro and WinNT. no support yet for <pty< and >pty> These are likely to be implemented as "<" and ">" with binmode on, not sure. no support for file(1,n) descriptors higher than 2 (stderr) Win32 only allows passing explicit fds 0, 1, and 2. If you really, really need to pass file(1,n) handles, us Win32API:: GetOsFHandle() or ::FdGetOsFHandle() to get the integer handle and pass it to the child process using the command line, environment, stdin, interme- diary file(1,n), or other IPC mechnism. Then use that handle in(1,8) the child (Win32API.pm provides ways to reconstitute Perl file(1,n) handles from Win32 file(1,n) handles). no support for subroutine subprocesses (CODE refs) Can't fork(), so the subroutines would have no context, and clo- sures certainly have no meaning Perhaps with Win32 fork() emulation, this can be supported in(1,8) a limited fashion, but there are other very serious problems with that: all parent fds get dup()ed in(1,8) to the thread emulating the forked process, and that keeps the parent from being able to close(2,7,n) all of the appropriate fds. no support for init => sub {} routines. Win32 processes are created from scratch, there is no way to do an init routine that will affect the running child. Some limited sup- port might be implemented one day, do chdir() and %ENV changes can be made. signals Win32 does not fully support signals. signal(2,7)() is likely to cause errors unless sending a signal(2,7) that Perl emulates, and "kill_kill()" is immediately fatal (there is no grace period). helper processes IPC::Run uses helper processes, one per redirected file(1,n), to adapt between the anonymous pipe(2,8) connected to the child and the TCP socket(2,7,n) connected to the parent. This is a waste of resources and will change in(1,8) the future to either use threads (instead of helper processes) or a WaitForMultipleObjects call (instead of select(2,7,2 select_tut)). Please contact me if(3,n) you can help with the WaitForMultipleObjects() approach; I haven't figured out how to get at it without C code. shutdown(2,8) pause There seems to be a pause of up to 1 second between when a child program exits and the corresponding sockets indicate that they are closed in(1,8) the parent. Not sure why. binmode binmode is not supported yet. The underpinnings are implemented, just ask if(3,n) you need it. IPC::Run::IO IPC::Run::IO objects can be used on Unix to read(2,n,1 builtins) or write(1,2) arbitrary files. On Win32, they will need to use the same helper processes to adapt from non-select(2,7,2 select_tut)()able filehandles to select(2,7,2 select_tut)()able ones (or perhaps WaitForMultipleObjects() will work with them, not sure). startup race conditions There seems to be an occasional race condition between child process startup and pipe(2,8) closings. It seems like if(3,n) the child is not fully created by the time(1,2,n) CreateProcess returns and we close(2,7,n) the TCP socket(2,7,n) being handed to it, the parent socket(2,7,n) can also get closed. This is seen with the Win32 pumper applications, not the "real" child process being spawned. I assume this is because the kernel hasn't gotten around to incre- menting the reference count on the child's end (since the child was slow in(1,8) starting), so the parent's closing of the child end causes the socket(2,7,n) to be closed, thus closing the parent socket. Being a race condition, it's hard to reproduce, but I encountered it while testing this code on a drive share to a samba box. In this case, it takes t/run.t a long time(1,2,n) to spawn it's chile pro- cesses (the parent hangs in(1,8) the first select(2,7,2 select_tut) for several seconds until the child emits any debugging output). I have not seen it on local drives, and can't reproduce it at will, unfortunately. The symptom is a "bad file(1,n) descriptor in(1,8) select(2,7,2 select_tut)()" error(8,n), and, by turning on debugging, it's possible to see that select(2,7,2 select_tut)() is being called on a no longer open(2,3,n) file(1,n) descriptor that was returned from the _socket() routine in(1,8) Win32Helper. There's a new confess() that checks for this ("PARENT_HANDLE no longer open(2,3,n)"), but I haven't been able to reproduce it (typically). LIMITATIONS On Unix, requires a system that supports "waitpid( $pid, WNOHANG )" so it can tell if(3,n) a child process is still running. PTYs don't seem to be non-blocking on some versions of Solaris. Here's a test script contributed by Borislav Deianov <borislav@ensim.com> to see if(3,n) you have the problem. If it dies, you have the problem. #!/usr/bin/perl use IPC::Run qw(run); use Fcntl; use IO::Pty; sub makecmd { return ['perl', '-e', '<STDIN>, print "\n" x '.$_[0].'; while(<STDIN>){last if(3,n) /end/}']; } #pipe(2,8) R, W; #fcntl(W, F_SETFL, O_NONBLOCK); #while (syswrite(W, "\n", 1)) { $pipebuf++ }; #print "pipe(2,8) buffer size is $pipebuf\n"; my $pipebuf=4096; my $in(1,8) = "\n" x ($pipebuf * 2) . "end\n"; my $out; $SIG{ALRM} = sub { die "Never completed!\n" } ; print "reading from scalar via pipe..."; alarm(1,2)( 2 ) ; run(makecmd($pipebuf * 2), '<', \$in(1,8), '>', \$out); alarm(1,2)( 0 ); print "done\n"; print "reading from code via pipe... "; alarm(1,2)( 2 ) ; run(makecmd($pipebuf * 3), '<', sub { $t = $in(1,8); undef $in(1,8); $t}, '>', \$out); alarm(1,2)( 0 ) ; print "done\n"; $pty = IO::Pty->new(); $pty->blocking(0); $slave = $pty->slave(); while ($pty->syswrite("\n", 1)) { $ptybuf++ }; print "pty buffer size is $ptybuf\n"; $in(1,8) = "\n" x ($ptybuf * 3) . "end\n"; print "reading via pty... "; alarm(1,2)( 2 ) ; run(makecmd($ptybuf * 3), '<pty<', \$in(1,8), '>', \$out); alarm(1,2)(0); print "done\n"; No support for ';', '&&', '||', '{ ... }', etc: use perl's, since run() returns TRUE when the command exits with a 0 result code. Does not provide shell-like string(3,n) interpolation. No support for "cd", "setenv", or "export": do these in(1,8) an init() sub run( \cmd, ... init => sub { chdir $dir or die $! ; $ENV{FOO}='BAR' } ) ; Timeout calculation does not allow absolute times, or specification of days, months, etc. WARNING: Function coprocesses ("run \&foo, ...") suffer from two limi- tations. The first is that it is difficult to close(2,7,n) all filehandles the child inherits from the parent, since there is no way to scan all open(2,3,n) FILEHANDLEs in(1,8) Perl and it both painful and a bit dangerous to close(2,7,n) all open(2,3,n) file(1,n) descriptors with "POSIX::close()". Painful because we can't tell which fds are open(2,3,n) at the POSIX level, either, so we'd have to scan all possible fds and close(2,7,n) any that we don't want open(2,3,n) (normally "exec(3,n,1 builtins)()" closes any non-inheritable but we don't "exec(3,n,1 builtins)()" for &sub processes. The second problem is that Perl's DESTROY subs and other on-exit cleanup gets(3,n) run in(1,8) the child process. If objects are instantiated in(1,8) the parent before the child is forked, the the DESTROY will get run once in(1,8) the parent and once in(1,8) the child. When coprocess subs exit(3,n,1 builtins), POSIX::exit is called to work around this, but it means that objects that are still referred to at that time(1,2,n) are not cleaned up. So setting package vars or closure vars to point to objects that rely on DESTROY to affect things outside the process (files, etc), will lead to bugs. I goofed on the syntax: "<pipe(2,8)" vs. "<pty<" and ">filename" are both oddities. TODO Allow one harness to "adopt" another: $new_h = harness \@cmd2 ; $h->adopt( $new_h ) ; Close all filehandles not explicitly marked to stay open. The problem with this one is that there's no good way to scan all open(2,3,n) FILEHANDLEs in(1,8) Perl, yet you don't want child processes inher- iting handles willy-nilly. INSPIRATION Well, select(2,7,2 select_tut)() and waitpid() badly needed wrapping, and open3() isn't open-minded enough for me. The shell-like API inspired by a message Russ Allbery sent to perl5-porters, which included: I've thought for some time(1,2,n) that it would be nice(1,2) to have a module that could handle full Bourne shell pipe(2,8) syntax internally, with fork and exec(3,n,1 builtins), without ever invoking a shell. Something that you could give things like: pipeopen (PIPE, [ qw/cat file(1,n)/ ], '|', [ 'analyze', @args ], '>&3'); Message ylln51p2b6.fsf@windlord.stanford.edu, on 2000/02/04. AUTHOR Barrie Slaymaker <barries@slaysys.com>, with numerous suggestions by p5p. perl v5.8.5 2003-09-26 IPC::Run(3)