2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 * Subprocess library, modeled after Python's subprocess module
19 * (http://docs.python.org/2/library/subprocess.html)
21 * This library defines one class (Subprocess) which represents a child
22 * process. Subprocess has two constructors: one that takes a vector<string>
23 * and executes the given executable without using the shell, and one
24 * that takes a string and executes the given command using the shell.
25 * Subprocess allows you to redirect the child's standard input, standard
26 * output, and standard error to/from child descriptors in the parent,
27 * or to create communication pipes between the child and the parent.
29 * The simplest example is a thread-safe [1] version of the system() library
31 * Subprocess(cmd).wait();
32 * which executes the command using the default shell and waits for it
33 * to complete, returning the exit status.
35 * A thread-safe [1] version of popen() (type="r", to read from the child):
36 * Subprocess proc(cmd, Subprocess::pipeStdout());
37 * // read from proc.stdout()
40 * A thread-safe [1] version of popen() (type="w", to write to the child):
41 * Subprocess proc(cmd, Subprocess::pipeStdin());
42 * // write to proc.stdin()
45 * If you want to redirect both stdin and stdout to pipes, you can, but note
46 * that you're subject to a variety of deadlocks. You'll want to use
47 * nonblocking I/O, like the callback version of communicate().
49 * The string or IOBuf-based variants of communicate() are the simplest way
50 * to communicate with a child via its standard input, standard output, and
51 * standard error. They buffer everything in memory, so they are not great
52 * for large amounts of data (or long-running processes), but they are much
53 * simpler than the callback version.
55 * == A note on thread-safety ==
57 * [1] "thread-safe" refers ONLY to the fact that Subprocess is very careful
58 * to fork in a way that does not cause grief in multithreaded programs.
60 * Caveat: If your system does not have the atomic pipe2 system call, it is
61 * not safe to concurrently call Subprocess from different threads.
62 * Therefore, it is best to have a single thread be responsible for spawning
65 * A particular instances of Subprocess is emphatically **not** thread-safe.
66 * If you need to simultaneously communicate via the pipes, and interact
67 * with the Subprocess state, your best bet is to:
68 * - takeOwnershipOfPipes() to separate the pipe I/O from the subprocess.
69 * - Only interact with the Subprocess from one thread at a time.
71 * The current implementation of communicate() cannot be safely interrupted.
72 * To do so correctly, one would need to use EventFD, or open a dedicated
73 * pipe to be messaged from a different thread -- in particular, kill() will
74 * not do, since a descendant may keep the pipes open indefinitely.
76 * So, once you call communicate(), you must wait for it to return, and not
77 * touch the pipes from other threads. closeParentFd() is emphatically
78 * unsafe to call concurrently, and even sendSignal() is not a good idea.
79 * You can perhaps give the Subprocess's PID to a different thread before
80 * starting communicate(), and use that PID to send a signal without
81 * accessing the Subprocess object. In that case, you will need a mutex
82 * that ensures you don't wait() before you sent said signal. In a
83 * nutshell, don't do this.
85 * In fact, signals are inherently concurrency-unsafe on Unix: if you signal
86 * a PID, while another thread is in waitpid(), the signal may fire either
87 * before or after the process is reaped. This means that your signal can,
88 * in pathological circumstances, be delivered to the wrong process (ouch!).
89 * To avoid this, you should only use non-blocking waits (i.e. poll()), and
90 * make sure to serialize your signals (i.e. kill()) with the waits --
91 * either wait & signal from the same thread, or use a mutex.
96 #include <sys/types.h>
108 #include <boost/container/flat_map.hpp>
109 #include <boost/operators.hpp>
111 #include <folly/Exception.h>
112 #include <folly/File.h>
113 #include <folly/FileUtil.h>
114 #include <folly/Function.h>
115 #include <folly/gen/String.h>
116 #include <folly/io/IOBufQueue.h>
117 #include <folly/MapUtil.h>
118 #include <folly/Portability.h>
119 #include <folly/Range.h>
124 * Class to wrap a process return code.
127 class ProcessReturnCode {
128 friend class Subprocess;
131 // Subprocess starts in the constructor, so this state designates only
132 // default-initialized or moved-out ProcessReturnCodes.
139 // Default-initialized for convenience. Subprocess::returnCode() will
140 // never produce this value.
141 ProcessReturnCode() : ProcessReturnCode(RV_NOT_STARTED) {}
143 // Trivially copyable
144 ProcessReturnCode(const ProcessReturnCode& p) = default;
145 ProcessReturnCode& operator=(const ProcessReturnCode& p) = default;
146 // Non-default move: In order for Subprocess to be movable, the "moved
147 // out" state must not be "running", or ~Subprocess() will abort.
148 ProcessReturnCode(ProcessReturnCode&& p) noexcept;
149 ProcessReturnCode& operator=(ProcessReturnCode&& p) noexcept;
152 * Process state. One of:
153 * NOT_STARTED: process hasn't been started successfully
154 * RUNNING: process is currently running
155 * EXITED: process exited (successfully or not)
156 * KILLED: process was killed by a signal.
161 * Helper wrappers around state().
163 bool notStarted() const { return state() == NOT_STARTED; }
164 bool running() const { return state() == RUNNING; }
165 bool exited() const { return state() == EXITED; }
166 bool killed() const { return state() == KILLED; }
169 * Exit status. Only valid if state() == EXITED; throws otherwise.
171 int exitStatus() const;
174 * Signal that caused the process's termination. Only valid if
175 * state() == KILLED; throws otherwise.
177 int killSignal() const;
180 * Was a core file generated? Only valid if state() == KILLED; throws
183 bool coreDumped() const;
186 * String representation; one of
189 * "exited with status <status>"
190 * "killed by signal <signal>"
191 * "killed by signal <signal> (core dumped)"
193 std::string str() const;
196 * Helper function to enforce a precondition based on this.
197 * Throws std::logic_error if in an unexpected state.
199 void enforce(State state) const;
201 explicit ProcessReturnCode(int rv) : rawStatus_(rv) { }
202 static constexpr int RV_NOT_STARTED = -2;
203 static constexpr int RV_RUNNING = -1;
209 * Base exception thrown by the Subprocess methods.
211 class SubprocessError : public std::exception {};
214 * Exception thrown by *Checked methods of Subprocess.
216 class CalledProcessError : public SubprocessError {
218 explicit CalledProcessError(ProcessReturnCode rc);
219 ~CalledProcessError() throw() = default;
220 const char* what() const throw() override { return what_.c_str(); }
221 ProcessReturnCode returnCode() const { return returnCode_; }
223 ProcessReturnCode returnCode_;
228 * Exception thrown if the subprocess cannot be started.
230 class SubprocessSpawnError : public SubprocessError {
232 SubprocessSpawnError(const char* executable, int errCode, int errnoValue);
233 ~SubprocessSpawnError() throw() = default;
234 const char* what() const throw() override { return what_.c_str(); }
235 int errnoValue() const { return errnoValue_; }
247 static const int CLOSE = -1;
248 static const int PIPE = -2;
249 static const int PIPE_IN = -3;
250 static const int PIPE_OUT = -4;
253 * See Subprocess::Options::dangerousPostForkPreExecCallback() for usage.
254 * Every derived class should include the following warning:
256 * DANGER: This class runs after fork in a child processes. Be fast, the
257 * parent thread is waiting, but remember that other parent threads are
258 * running and may mutate your state. Avoid mutating any data belonging to
259 * the parent. Avoid interacting with non-POD data that originated in the
260 * parent. Avoid any libraries that may internally reference non-POD data.
261 * Especially beware parent mutexes -- for example, glog's LOG() uses one.
263 struct DangerousPostForkPreExecCallback {
264 virtual ~DangerousPostForkPreExecCallback() {}
265 // This must return 0 on success, or an `errno` error code.
266 virtual int operator()() = 0;
270 * Class representing various options: file descriptor behavior, and
271 * whether to use $PATH for searching for the executable,
273 * By default, we don't use $PATH, file descriptors are closed if
274 * the close-on-exec flag is set (fcntl FD_CLOEXEC) and inherited
277 class Options : private boost::orable<Options> {
278 friend class Subprocess;
280 Options() {} // E.g. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58328
283 * Change action for file descriptor fd.
285 * "action" may be another file descriptor number (dup2()ed before the
286 * child execs), or one of CLOSE, PIPE_IN, and PIPE_OUT.
288 * CLOSE: close the file descriptor in the child
289 * PIPE_IN: open a pipe *from* the child
290 * PIPE_OUT: open a pipe *to* the child
292 * PIPE is a shortcut; same as PIPE_IN for stdin (fd 0), same as
293 * PIPE_OUT for stdout (fd 1) or stderr (fd 2), and an error for
294 * other file descriptors.
296 Options& fd(int fd, int action);
299 * Shortcut to change the action for standard input.
301 Options& stdin(int action) { return fd(STDIN_FILENO, action); }
304 * Shortcut to change the action for standard output.
306 Options& stdout(int action) { return fd(STDOUT_FILENO, action); }
309 * Shortcut to change the action for standard error.
310 * Note that stderr(1) will redirect the standard error to the same
311 * file descriptor as standard output; the equivalent of bash's "2>&1"
313 Options& stderr(int action) { return fd(STDERR_FILENO, action); }
315 Options& pipeStdin() { return fd(STDIN_FILENO, PIPE_IN); }
316 Options& pipeStdout() { return fd(STDOUT_FILENO, PIPE_OUT); }
317 Options& pipeStderr() { return fd(STDERR_FILENO, PIPE_OUT); }
320 * Close all other fds (other than standard input, output, error,
321 * and file descriptors explicitly specified with fd()).
323 * This is potentially slow; it's generally a better idea to
324 * set the close-on-exec flag on all file descriptors that shouldn't
325 * be inherited by the child.
327 * Even with this option set, standard input, output, and error are
328 * not closed; use stdin(CLOSE), stdout(CLOSE), stderr(CLOSE) if you
331 Options& closeOtherFds() { closeOtherFds_ = true; return *this; }
334 * Use the search path ($PATH) when searching for the executable.
336 Options& usePath() { usePath_ = true; return *this; }
339 * Change the child's working directory, after the vfork.
341 Options& chdir(const std::string& dir) { childDir_ = dir; return *this; }
345 * Child will receive a signal when the parent exits.
347 Options& parentDeathSignal(int sig) {
348 parentDeathSignal_ = sig;
354 * Child will be made a process group leader when it starts. Upside: one
355 * can reliably all its kill non-daemonizing descendants. Downside: the
356 * child will not receive Ctrl-C etc during interactive use.
358 Options& processGroupLeader() {
359 processGroupLeader_ = true;
364 * *** READ THIS WHOLE DOCBLOCK BEFORE USING ***
366 * Run this callback in the child after the fork, just before the
367 * exec(), and after the child's state has been completely set up:
368 * - signal handlers have been reset to default handling and unblocked
369 * - the working directory was set
370 * - closed any file descriptors specified via Options()
371 * - set child process flags (see code)
373 * This is EXTREMELY DANGEROUS. For example, this innocuous-looking code
374 * can cause a fraction of your Subprocess launches to hang forever:
376 * LOG(INFO) << "Hello from the child";
378 * The reason is that glog has an internal mutex. If your fork() happens
379 * when the parent has the mutex locked, the child will wait forever.
383 * - Be quick -- the parent thread is blocked until you exit.
384 * - Remember that other parent threads are running, and may mutate your
386 * - Avoid mutating any data belonging to the parent.
387 * - Avoid interacting with non-POD data that came from the parent.
388 * - Avoid any libraries that may internally reference non-POD state.
389 * - Especially beware parent mutexes, e.g. LOG() uses a global mutex.
390 * - Avoid invoking the parent's destructors (you can accidentally
391 * delete files, terminate network connections, etc).
392 * - Read http://ewontfix.com/7/
394 Options& dangerousPostForkPreExecCallback(
395 DangerousPostForkPreExecCallback* cob) {
396 dangerousPostForkPreExecCallback_ = cob;
401 * Helpful way to combine Options.
403 Options& operator|=(const Options& other);
406 typedef boost::container::flat_map<int, int> FdMap;
408 bool closeOtherFds_{false};
409 bool usePath_{false};
410 std::string childDir_; // "" keeps the parent's working directory
412 int parentDeathSignal_{0};
414 bool processGroupLeader_{false};
415 DangerousPostForkPreExecCallback*
416 dangerousPostForkPreExecCallback_{nullptr};
419 static Options pipeStdin() { return Options().stdin(PIPE); }
420 static Options pipeStdout() { return Options().stdout(PIPE); }
421 static Options pipeStderr() { return Options().stderr(PIPE); }
423 // Non-copiable, but movable
424 Subprocess(const Subprocess&) = delete;
425 Subprocess& operator=(const Subprocess&) = delete;
426 Subprocess(Subprocess&&) = default;
427 Subprocess& operator=(Subprocess&&) = default;
430 * Create an uninitialized subprocess.
432 * In this state it can only be destroyed, or assigned to using the move
433 * assignment operator.
438 * Create a subprocess from the given arguments. argv[0] must be listed.
439 * If not-null, executable must be the actual executable
440 * being used (otherwise it's the same as argv[0]).
442 * If env is not-null, it must contain name=value strings to be used
443 * as the child's environment; otherwise, we inherit the environment
444 * from the parent. env must be null if options.usePath is set.
447 const std::vector<std::string>& argv,
448 const Options& options = Options(),
449 const char* executable = nullptr,
450 const std::vector<std::string>* env = nullptr);
454 * Create a subprocess run as a shell command (as shell -c 'command')
456 * The shell to use is taken from the environment variable $SHELL,
457 * or /bin/sh if $SHELL is unset.
460 const std::string& cmd,
461 const Options& options = Options(),
462 const std::vector<std::string>* env = nullptr);
465 //// The methods below only manipulate the process state, and do not
466 //// affect its communication pipes.
470 * Return the child's pid, or -1 if the child wasn't successfully spawned
471 * or has already been wait()ed upon.
476 * Return the child's status (as per wait()) if the process has already
477 * been waited on, -1 if the process is still running, or -2 if the
478 * process hasn't been successfully started. NOTE that this does not call
479 * waitpid() or Subprocess::poll(), but simply returns the status stored
480 * in the Subprocess object.
482 ProcessReturnCode returnCode() const { return returnCode_; }
485 * Poll the child's status and return it. Return the exit status if the
486 * subprocess had quit, or RUNNING otherwise. Throws an std::logic_error
487 * if called on a Subprocess whose status is no longer RUNNING. No other
488 * exceptions are possible. Aborts on egregious violations of contract,
489 * e.g. if you wait for the underlying process without going through this
490 * Subprocess instance.
492 ProcessReturnCode poll();
495 * Poll the child's status. If the process is still running, return false.
496 * Otherwise, return true if the process exited with status 0 (success),
497 * or throw CalledProcessError if the process exited with a non-zero status.
502 * Wait for the process to terminate and return its status. Like poll(),
503 * the only exception this can throw is std::logic_error if you call this
504 * on a Subprocess whose status is RUNNING. Aborts on egregious
505 * violations of contract, like an out-of-band waitpid(p.pid(), 0, 0).
507 ProcessReturnCode wait();
510 * Wait for the process to terminate, throw if unsuccessful.
515 * Send a signal to the child. Shortcuts for the commonly used Unix
518 void sendSignal(int signal);
519 void terminate() { sendSignal(SIGTERM); }
520 void kill() { sendSignal(SIGKILL); }
523 //// The methods below only affect the process's communication pipes, but
524 //// not its return code or state (they do not poll() or wait()).
528 * Communicate with the child until all pipes to/from the child are closed.
530 * The input buffer is written to the process' stdin pipe, and data is read
531 * from the stdout and stderr pipes. Non-blocking I/O is performed on all
532 * pipes simultaneously to avoid deadlocks.
534 * The stdin pipe will be closed after the full input buffer has been written.
535 * An error will be thrown if a non-empty input buffer is supplied but stdin
536 * was not configured as a pipe.
538 * Returns a pair of buffers containing the data read from stdout and stderr.
539 * If stdout or stderr is not a pipe, an empty IOBuf queue will be returned
540 * for the respective buffer.
542 * Note that communicate() and communicateIOBuf() both return when all
543 * pipes to/from the child are closed; the child might stay alive after
544 * that, so you must still wait().
546 * communicateIOBuf() uses IOBufQueue for buffering (which has the
547 * advantage that it won't try to allocate all data at once), but it does
548 * store the subprocess's entire output in memory before returning.
550 * communicate() uses strings for simplicity.
552 std::pair<IOBufQueue, IOBufQueue> communicateIOBuf(
553 IOBufQueue input = IOBufQueue());
555 std::pair<std::string, std::string> communicate(
556 StringPiece input = StringPiece());
559 * Communicate with the child until all pipes to/from the child are closed.
563 * readCallback(pfd, cfd) will be called whenever there's data available
564 * on any pipe *from* the child (PIPE_OUT). pfd is the file descriptor
565 * in the parent (that you use to read from); cfd is the file descriptor
566 * in the child (used for identifying the stream; 1 = child's standard
567 * output, 2 = child's standard error, etc)
569 * writeCallback(pfd, cfd) will be called whenever a pipe *to* the child is
570 * writable (PIPE_IN). pfd is the file descriptor in the parent (that you
571 * use to write to); cfd is the file descriptor in the child (used for
572 * identifying the stream; 0 = child's standard input, etc)
574 * The read and write callbacks must read from / write to pfd and return
575 * false during normal operation. Return true to tell communicate() to
576 * close the pipe. For readCallback, this might send SIGPIPE to the
577 * child, or make its writes fail with EPIPE, so you should generally
578 * avoid returning true unless you've reached end-of-file.
580 * communicate() returns when all pipes to/from the child are closed; the
581 * child might stay alive after that, so you must still wait().
582 * Conversely, the child may quit long before its pipes are closed, since
583 * its descendants can keep them alive forever.
585 * Most users won't need to use this callback version; the simpler version
586 * of communicate (which buffers data in memory) will probably work fine.
588 * == Things you must get correct ==
590 * 1) You MUST consume all data passed to readCallback (or return true to
591 * close the pipe). Similarly, you MUST write to a writable pipe (or
592 * return true to close the pipe). To do otherwise is an error that can
593 * result in a deadlock. You must do this even for pipes you are not
596 * 2) pfd is nonblocking, so be prepared for read() / write() to return -1
597 * and set errno to EAGAIN (in which case you should return false). Use
598 * readNoInt() from FileUtil.h to handle interrupted reads for you.
600 * 3) Your callbacks MUST NOT call any of the Subprocess methods that
601 * manipulate the pipe FDs. Check the docblocks, but, for example,
602 * neither closeParentFd (return true instead) nor takeOwnershipOfPipes
603 * are safe. Stick to reading/writing from pfd, as appropriate.
607 * 1) See ReadLinesCallback for an easy way to consume the child's output
608 * streams line-by-line (or tokenized by another delimiter).
610 * 2) "Wait until the descendants close the pipes" is usually the behavior
611 * you want, since the descendants may have something to say even if the
612 * immediate child is dead. If you need to be able to force-close all
613 * parent FDs, communicate() will NOT work for you. Do it your own way by
614 * using takeOwnershipOfPipes().
616 * Why not? You can return "true" from your callbacks to sever active
617 * pipes, but inactive ones can remain open indefinitely. It is
618 * impossible to safely close inactive pipes while another thread is
619 * blocked in communicate(). This is BY DESIGN. Racing communicate()'s
620 * read/write callbacks can result in wrong I/O and data corruption. This
621 * class would need internal synchronization and timeouts, a poor and
622 * expensive implementation choice, in order to make closeParentFd()
625 using FdCallback = folly::Function<bool(int, int)>;
626 void communicate(FdCallback readCallback, FdCallback writeCallback);
629 * A readCallback for Subprocess::communicate() that helps you consume
630 * lines (or other delimited pieces) from your subprocess's file
631 * descriptors. Use the readLinesCallback() helper to get template
632 * deduction. For example:
634 * subprocess.communicate(
635 * Subprocess::readLinesCallback(
636 * [](int fd, folly::StringPiece s) {
637 * std::cout << fd << " said: " << s;
638 * return false; // Keep reading from the child
641 * [](int pdf, int cfd){ return true; } // Don't write to the child
644 * If a file line exceeds maxLineLength, your callback will get some
645 * initial chunks of maxLineLength with no trailing delimiters. The final
646 * chunk of a line is delimiter-terminated iff the delimiter was present
647 * in the input. In particular, the last line in a file always lacks a
648 * delimiter -- so if a file ends on a delimiter, the final line is empty.
650 * Like a regular communicate() callback, your fdLineCb() normally returns
651 * false. It may return true to tell Subprocess to close the underlying
652 * file descriptor. The child process may then receive SIGPIPE or get
653 * EPIPE errors on writes.
655 template <class Callback>
656 class ReadLinesCallback {
658 // Binds an FD to the client-provided FD+line callback
659 struct StreamSplitterCallback {
660 StreamSplitterCallback(Callback& cb, int fd) : cb_(cb), fd_(fd) { }
661 // The return value semantics are inverted vs StreamSplitter
662 bool operator()(StringPiece s) { return !cb_(fd_, s); }
666 typedef gen::StreamSplitter<StreamSplitterCallback> LineSplitter;
668 explicit ReadLinesCallback(
670 uint64_t maxLineLength = 0, // No line length limit by default
671 char delimiter = '\n',
672 uint64_t bufSize = 1024
673 ) : fdLineCb_(std::forward<Callback>(fdLineCb)),
674 maxLineLength_(maxLineLength),
675 delimiter_(delimiter),
678 bool operator()(int pfd, int cfd) {
679 // Make a splitter for this cfd if it doesn't already exist
680 auto it = fdToSplitter_.find(cfd);
681 auto& splitter = (it != fdToSplitter_.end()) ? it->second
682 : fdToSplitter_.emplace(cfd, LineSplitter(
683 delimiter_, StreamSplitterCallback(fdLineCb_, cfd), maxLineLength_
685 // Read as much as we can from this FD
688 ssize_t ret = readNoInt(pfd, buf, bufSize_);
689 if (ret == -1 && errno == EAGAIN) { // No more data for now
692 checkUnixError(ret, "read");
693 if (ret == 0) { // Reached end-of-file
694 splitter.flush(); // Ignore return since the file is over anyway
697 if (!splitter(StringPiece(buf, ret))) {
698 return true; // The callback told us to stop
705 const uint64_t maxLineLength_;
706 const char delimiter_;
707 const uint64_t bufSize_;
708 // We lazily make splitters for all cfds that get used.
709 std::unordered_map<int, LineSplitter> fdToSplitter_;
712 // Helper to enable template deduction
713 template <class Callback>
714 static auto readLinesCallback(
716 uint64_t maxLineLength = 0, // No line length limit by default
717 char delimiter = '\n',
718 uint64_t bufSize = 1024)
719 -> ReadLinesCallback<typename std::decay<Callback>::type> {
720 return ReadLinesCallback<typename std::decay<Callback>::type>(
721 std::forward<Callback>(fdLineCb), maxLineLength, delimiter, bufSize);
725 * communicate() callbacks can use this to temporarily enable/disable
726 * notifications (callbacks) for a pipe to/from the child. By default,
727 * all are enabled. Useful for "chatty" communication -- you want to
728 * disable write callbacks until you receive the expected message.
730 * Disabling a pipe does not free you from the requirement to consume all
731 * incoming data. Failing to do so will easily create deadlock bugs.
733 * Throws if the childFd is not known.
735 void enableNotifications(int childFd, bool enabled);
738 * Are notifications for one pipe to/from child enabled? Throws if the
739 * childFd is not known.
741 bool notificationsEnabled(int childFd) const;
744 //// The following methods are meant for the cases when communicate() is
745 //// not suitable. You should not need them when you call communicate(),
746 //// and, in fact, it is INHERENTLY UNSAFE to use closeParentFd() or
747 //// takeOwnershipOfPipes() from a communicate() callback.
751 * Close the parent file descriptor given a file descriptor in the child.
752 * DO NOT USE from communicate() callbacks; make them return true instead.
754 void closeParentFd(int childFd);
757 * Set all pipes from / to child to be non-blocking. communicate() does
760 void setAllNonBlocking();
763 * Get parent file descriptor corresponding to the given file descriptor
764 * in the child. Throws if childFd isn't a pipe (PIPE_IN / PIPE_OUT).
765 * Do not close() the returned file descriptor; use closeParentFd, above.
767 int parentFd(int childFd) const {
768 return pipes_[findByChildFd(childFd)].pipe.fd();
770 int stdin() const { return parentFd(0); }
771 int stdout() const { return parentFd(1); }
772 int stderr() const { return parentFd(2); }
775 * The child's pipes are logically separate from the process metadata
776 * (they may even be kept alive by the child's descendants). This call
777 * lets you manage the pipes' lifetime separetely from the lifetime of the
780 * After this call, the Subprocess instance will have no knowledge of
781 * these pipes, and the caller assumes responsibility for managing their
782 * lifetimes. Pro-tip: prefer to explicitly close() the pipes, since
783 * folly::File would otherwise silently suppress I/O errors.
785 * No, you may NOT call this from a communicate() callback.
788 ChildPipe(int fd, folly::File&& ppe) : childFd(fd), pipe(std::move(ppe)) {}
790 folly::File pipe; // Owns the parent FD
792 std::vector<ChildPipe> takeOwnershipOfPipes();
795 static const int RV_RUNNING = ProcessReturnCode::RV_RUNNING;
796 static const int RV_NOT_STARTED = ProcessReturnCode::RV_NOT_STARTED;
798 // spawn() sets up a pipe to read errors from the child,
799 // then calls spawnInternal() to do the bulk of the work. Once
800 // spawnInternal() returns it reads the error pipe to see if the child
801 // encountered any errors.
803 std::unique_ptr<const char*[]> argv,
804 const char* executable,
805 const Options& options,
806 const std::vector<std::string>* env);
808 std::unique_ptr<const char*[]> argv,
809 const char* executable,
811 const std::vector<std::string>* env,
814 // Actions to run in child.
815 // Note that this runs after vfork(), so tread lightly.
816 // Returns 0 on success, or an errno value on failure.
817 int prepareChild(const Options& options,
818 const sigset_t* sigmask,
819 const char* childDir) const;
820 int runChild(const char* executable, char** argv, char** env,
821 const Options& options) const;
824 * Read from the error pipe, and throw SubprocessSpawnError if the child
825 * failed before calling exec().
827 void readChildErrorPipe(int pfd, const char* executable);
829 // Returns an index into pipes_. Throws std::invalid_argument if not found.
830 size_t findByChildFd(const int childFd) const;
833 ProcessReturnCode returnCode_{RV_NOT_STARTED};
836 * Represents a pipe between this process, and the child process (or its
837 * descendant). To interact with these pipes, you can use communicate(),
838 * or use parentFd() and related methods, or separate them from the
839 * Subprocess instance entirely via takeOwnershipOfPipes().
841 struct Pipe : private boost::totally_ordered<Pipe> {
842 folly::File pipe; // Our end of the pipe, wrapped in a File to auto-close.
843 int childFd = -1; // Identifies the pipe: what FD is this in the child?
844 int direction = PIPE_IN; // one of PIPE_IN / PIPE_OUT
845 bool enabled = true; // Are notifications enabled in communicate()?
847 bool operator<(const Pipe& other) const {
848 return childFd < other.childFd;
850 bool operator==(const Pipe& other) const {
851 return childFd == other.childFd;
855 // Populated at process start according to fdActions, empty after
856 // takeOwnershipOfPipes(). Sorted by childFd. Can only have elements
857 // erased, but not inserted, after being populated.
859 // The number of pipes between parent and child is assumed to be small,
860 // so we're happy with a vector here, even if it means linear erase.
861 std::vector<Pipe> pipes_;
864 inline Subprocess::Options& Subprocess::Options::operator|=(
865 const Subprocess::Options& other) {
866 if (this == &other) return *this;
868 for (auto& p : other.fdActions_) {
869 fdActions_[p.first] = p.second;
871 closeOtherFds_ |= other.closeOtherFds_;
872 usePath_ |= other.usePath_;
873 processGroupLeader_ |= other.processGroupLeader_;