2 * Copyright 2015 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.
93 #ifndef FOLLY_SUBPROCESS_H_
94 #define FOLLY_SUBPROCESS_H_
96 #include <sys/types.h>
108 #include <boost/container/flat_map.hpp>
109 #include <boost/operators.hpp>
111 #include <folly/File.h>
112 #include <folly/FileUtil.h>
113 #include <folly/gen/String.h>
114 #include <folly/io/IOBufQueue.h>
115 #include <folly/MapUtil.h>
116 #include <folly/Portability.h>
117 #include <folly/Range.h>
122 * Class to wrap a process return code.
125 class ProcessReturnCode {
126 friend class Subprocess;
135 // Trivially copyable
136 ProcessReturnCode(const ProcessReturnCode& p) = default;
137 ProcessReturnCode& operator=(const ProcessReturnCode& p) = default;
138 // Non-default move: In order for Subprocess to be movable, the "moved
139 // out" state must not be "running", or ~Subprocess() will abort.
140 ProcessReturnCode(ProcessReturnCode&& p) noexcept;
141 ProcessReturnCode& operator=(ProcessReturnCode&& p) noexcept;
144 * Process state. One of:
145 * NOT_STARTED: process hasn't been started successfully
146 * RUNNING: process is currently running
147 * EXITED: process exited (successfully or not)
148 * KILLED: process was killed by a signal.
153 * Helper wrappers around state().
155 bool notStarted() const { return state() == NOT_STARTED; }
156 bool running() const { return state() == RUNNING; }
157 bool exited() const { return state() == EXITED; }
158 bool killed() const { return state() == KILLED; }
161 * Exit status. Only valid if state() == EXITED; throws otherwise.
163 int exitStatus() const;
166 * Signal that caused the process's termination. Only valid if
167 * state() == KILLED; throws otherwise.
169 int killSignal() const;
172 * Was a core file generated? Only valid if state() == KILLED; throws
175 bool coreDumped() const;
178 * String representation; one of
181 * "exited with status <status>"
182 * "killed by signal <signal>"
183 * "killed by signal <signal> (core dumped)"
185 std::string str() const;
188 * Helper function to enforce a precondition based on this.
189 * Throws std::logic_error if in an unexpected state.
191 void enforce(State state) const;
193 explicit ProcessReturnCode(int rv) : rawStatus_(rv) { }
194 static constexpr int RV_NOT_STARTED = -2;
195 static constexpr int RV_RUNNING = -1;
201 * Base exception thrown by the Subprocess methods.
203 class SubprocessError : public std::exception {};
206 * Exception thrown by *Checked methods of Subprocess.
208 class CalledProcessError : public SubprocessError {
210 explicit CalledProcessError(ProcessReturnCode rc);
211 ~CalledProcessError() throw() = default;
212 const char* what() const throw() FOLLY_OVERRIDE { return what_.c_str(); }
213 ProcessReturnCode returnCode() const { return returnCode_; }
215 ProcessReturnCode returnCode_;
220 * Exception thrown if the subprocess cannot be started.
222 class SubprocessSpawnError : public SubprocessError {
224 SubprocessSpawnError(const char* executable, int errCode, int errnoValue);
225 ~SubprocessSpawnError() throw() = default;
226 const char* what() const throw() FOLLY_OVERRIDE { return what_.c_str(); }
227 int errnoValue() const { return errnoValue_; }
239 static const int CLOSE = -1;
240 static const int PIPE = -2;
241 static const int PIPE_IN = -3;
242 static const int PIPE_OUT = -4;
245 * Class representing various options: file descriptor behavior, and
246 * whether to use $PATH for searching for the executable,
248 * By default, we don't use $PATH, file descriptors are closed if
249 * the close-on-exec flag is set (fcntl FD_CLOEXEC) and inherited
252 class Options : private boost::orable<Options> {
253 friend class Subprocess;
255 Options() {} // E.g. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58328
258 * Change action for file descriptor fd.
260 * "action" may be another file descriptor number (dup2()ed before the
261 * child execs), or one of CLOSE, PIPE_IN, and PIPE_OUT.
263 * CLOSE: close the file descriptor in the child
264 * PIPE_IN: open a pipe *from* the child
265 * PIPE_OUT: open a pipe *to* the child
267 * PIPE is a shortcut; same as PIPE_IN for stdin (fd 0), same as
268 * PIPE_OUT for stdout (fd 1) or stderr (fd 2), and an error for
269 * other file descriptors.
271 Options& fd(int fd, int action);
274 * Shortcut to change the action for standard input.
276 Options& stdin(int action) { return fd(STDIN_FILENO, action); }
279 * Shortcut to change the action for standard output.
281 Options& stdout(int action) { return fd(STDOUT_FILENO, action); }
284 * Shortcut to change the action for standard error.
285 * Note that stderr(1) will redirect the standard error to the same
286 * file descriptor as standard output; the equivalent of bash's "2>&1"
288 Options& stderr(int action) { return fd(STDERR_FILENO, action); }
290 Options& pipeStdin() { return fd(STDIN_FILENO, PIPE_IN); }
291 Options& pipeStdout() { return fd(STDOUT_FILENO, PIPE_OUT); }
292 Options& pipeStderr() { return fd(STDERR_FILENO, PIPE_OUT); }
295 * Close all other fds (other than standard input, output, error,
296 * and file descriptors explicitly specified with fd()).
298 * This is potentially slow; it's generally a better idea to
299 * set the close-on-exec flag on all file descriptors that shouldn't
300 * be inherited by the child.
302 * Even with this option set, standard input, output, and error are
303 * not closed; use stdin(CLOSE), stdout(CLOSE), stderr(CLOSE) if you
306 Options& closeOtherFds() { closeOtherFds_ = true; return *this; }
309 * Use the search path ($PATH) when searching for the executable.
311 Options& usePath() { usePath_ = true; return *this; }
314 * Change the child's working directory, after the vfork.
316 Options& chdir(const std::string& dir) { childDir_ = dir; return *this; }
320 * Child will receive a signal when the parent exits.
322 Options& parentDeathSignal(int sig) {
323 parentDeathSignal_ = sig;
329 * Child will be made a process group leader when it starts. Upside: one
330 * can reliably all its kill non-daemonizing descendants. Downside: the
331 * child will not receive Ctrl-C etc during interactive use.
333 Options& processGroupLeader() {
334 processGroupLeader_ = true;
339 * Helpful way to combine Options.
341 Options& operator|=(const Options& other);
344 typedef boost::container::flat_map<int, int> FdMap;
346 bool closeOtherFds_{false};
347 bool usePath_{false};
348 std::string childDir_; // "" keeps the parent's working directory
350 int parentDeathSignal_{0};
352 bool processGroupLeader_{false};
355 static Options pipeStdin() { return Options().stdin(PIPE); }
356 static Options pipeStdout() { return Options().stdout(PIPE); }
357 static Options pipeStderr() { return Options().stderr(PIPE); }
359 // Non-copiable, but movable
360 Subprocess(const Subprocess&) = delete;
361 Subprocess& operator=(const Subprocess&) = delete;
362 Subprocess(Subprocess&&) = default;
363 Subprocess& operator=(Subprocess&&) = default;
366 * Create a subprocess from the given arguments. argv[0] must be listed.
367 * If not-null, executable must be the actual executable
368 * being used (otherwise it's the same as argv[0]).
370 * If env is not-null, it must contain name=value strings to be used
371 * as the child's environment; otherwise, we inherit the environment
372 * from the parent. env must be null if options.usePath is set.
375 const std::vector<std::string>& argv,
376 const Options& options = Options(),
377 const char* executable = nullptr,
378 const std::vector<std::string>* env = nullptr);
382 * Create a subprocess run as a shell command (as shell -c 'command')
384 * The shell to use is taken from the environment variable $SHELL,
385 * or /bin/sh if $SHELL is unset.
388 const std::string& cmd,
389 const Options& options = Options(),
390 const std::vector<std::string>* env = nullptr);
393 //// The methods below only manipulate the process state, and do not
394 //// affect its communication pipes.
398 * Return the child's pid, or -1 if the child wasn't successfully spawned
399 * or has already been wait()ed upon.
404 * Return the child's status (as per wait()) if the process has already
405 * been waited on, -1 if the process is still running, or -2 if the
406 * process hasn't been successfully started. NOTE that this does not call
407 * waitpid() or Subprocess::poll(), but simply returns the status stored
408 * in the Subprocess object.
410 ProcessReturnCode returnCode() const { return returnCode_; }
413 * Poll the child's status and return it. Return the exit status if the
414 * subprocess had quit, or RUNNING otherwise. Throws an std::logic_error
415 * if called on a Subprocess whose status is no longer RUNNING. No other
416 * exceptions are possible. Aborts on egregious violations of contract,
417 * e.g. if you wait for the underlying process without going through this
418 * Subprocess instance.
420 ProcessReturnCode poll();
423 * Poll the child's status. If the process is still running, return false.
424 * Otherwise, return true if the process exited with status 0 (success),
425 * or throw CalledProcessError if the process exited with a non-zero status.
430 * Wait for the process to terminate and return its status. Like poll(),
431 * the only exception this can throw is std::logic_error if you call this
432 * on a Subprocess whose status is RUNNING. Aborts on egregious
433 * violations of contract, like an out-of-band waitpid(p.pid(), 0, 0).
435 ProcessReturnCode wait();
438 * Wait for the process to terminate, throw if unsuccessful.
443 * Send a signal to the child. Shortcuts for the commonly used Unix
446 void sendSignal(int signal);
447 void terminate() { sendSignal(SIGTERM); }
448 void kill() { sendSignal(SIGKILL); }
451 //// The methods below only affect the process's communication pipes, but
452 //// not its return code or state (they do not poll() or wait()).
456 * Communicate with the child until all pipes to/from the child are closed.
458 * The input buffer is written to the process' stdin pipe, and data is read
459 * from the stdout and stderr pipes. Non-blocking I/O is performed on all
460 * pipes simultaneously to avoid deadlocks.
462 * The stdin pipe will be closed after the full input buffer has been written.
463 * An error will be thrown if a non-empty input buffer is supplied but stdin
464 * was not configured as a pipe.
466 * Returns a pair of buffers containing the data read from stdout and stderr.
467 * If stdout or stderr is not a pipe, an empty IOBuf queue will be returned
468 * for the respective buffer.
470 * Note that communicate() and communicateIOBuf() both return when all
471 * pipes to/from the child are closed; the child might stay alive after
472 * that, so you must still wait().
474 * communicateIOBuf() uses IOBufQueue for buffering (which has the
475 * advantage that it won't try to allocate all data at once), but it does
476 * store the subprocess's entire output in memory before returning.
478 * communicate() uses strings for simplicity.
480 std::pair<IOBufQueue, IOBufQueue> communicateIOBuf(
481 IOBufQueue input = IOBufQueue());
483 std::pair<std::string, std::string> communicate(
484 StringPiece input = StringPiece());
487 * Communicate with the child until all pipes to/from the child are closed.
491 * readCallback(pfd, cfd) will be called whenever there's data available
492 * on any pipe *from* the child (PIPE_OUT). pfd is the file descriptor
493 * in the parent (that you use to read from); cfd is the file descriptor
494 * in the child (used for identifying the stream; 1 = child's standard
495 * output, 2 = child's standard error, etc)
497 * writeCallback(pfd, cfd) will be called whenever a pipe *to* the child is
498 * writable (PIPE_IN). pfd is the file descriptor in the parent (that you
499 * use to write to); cfd is the file descriptor in the child (used for
500 * identifying the stream; 0 = child's standard input, etc)
502 * The read and write callbacks must read from / write to pfd and return
503 * false during normal operation. Return true to tell communicate() to
504 * close the pipe. For readCallback, this might send SIGPIPE to the
505 * child, or make its writes fail with EPIPE, so you should generally
506 * avoid returning true unless you've reached end-of-file.
508 * communicate() returns when all pipes to/from the child are closed; the
509 * child might stay alive after that, so you must still wait().
510 * Conversely, the child may quit long before its pipes are closed, since
511 * its descendants can keep them alive forever.
513 * Most users won't need to use this callback version; the simpler version
514 * of communicate (which buffers data in memory) will probably work fine.
516 * == Things you must get correct ==
518 * 1) You MUST consume all data passed to readCallback (or return true to
519 * close the pipe). Similarly, you MUST write to a writable pipe (or
520 * return true to close the pipe). To do otherwise is an error that can
521 * result in a deadlock. You must do this even for pipes you are not
524 * 2) pfd is nonblocking, so be prepared for read() / write() to return -1
525 * and set errno to EAGAIN (in which case you should return false). Use
526 * readNoInt() from FileUtil.h to handle interrupted reads for you.
528 * 3) Your callbacks MUST NOT call any of the Subprocess methods that
529 * manipulate the pipe FDs. Check the docblocks, but, for example,
530 * neither closeParentFd (return true instead) nor takeOwnershipOfPipes
531 * are safe. Stick to reading/writing from pfd, as appropriate.
535 * 1) See ReadLinesCallback for an easy way to consume the child's output
536 * streams line-by-line (or tokenized by another delimiter).
538 * 2) "Wait until the descendants close the pipes" is usually the behavior
539 * you want, since the descendants may have something to say even if the
540 * immediate child is dead. If you need to be able to force-close all
541 * parent FDs, communicate() will NOT work for you. Do it your own way by
542 * using takeOwnershipOfPipes().
544 * Why not? You can return "true" from your callbacks to sever active
545 * pipes, but inactive ones can remain open indefinitely. It is
546 * impossible to safely close inactive pipes while another thread is
547 * blocked in communicate(). This is BY DESIGN. Racing communicate()'s
548 * read/write callbacks can result in wrong I/O and data corruption. This
549 * class would need internal synchronization and timeouts, a poor and
550 * expensive implementation choice, in order to make closeParentFd()
553 typedef std::function<bool(int, int)> FdCallback;
554 void communicate(FdCallback readCallback, FdCallback writeCallback);
557 * A readCallback for Subprocess::communicate() that helps you consume
558 * lines (or other delimited pieces) from your subprocess's file
559 * descriptors. Use the readLinesCallback() helper to get template
560 * deduction. For example:
562 * auto read_cb = Subprocess::readLinesCallback(
563 * [](int fd, folly::StringPiece s) {
564 * std::cout << fd << " said: " << s;
565 * return false; // Keep reading from the child
568 * subprocess.communicate(
569 * // ReadLinesCallback contains StreamSplitter contains IOBuf, making
570 * // it noncopyable, whereas std::function must be copyable. So, we
571 * // keep the callback in a local, and instead pass a reference.
573 * [](int pdf, int cfd){ return true; } // Don't write to the child
576 * If a file line exceeds maxLineLength, your callback will get some
577 * initial chunks of maxLineLength with no trailing delimiters. The final
578 * chunk of a line is delimiter-terminated iff the delimiter was present
579 * in the input. In particular, the last line in a file always lacks a
580 * delimiter -- so if a file ends on a delimiter, the final line is empty.
582 * Like a regular communicate() callback, your fdLineCb() normally returns
583 * false. It may return true to tell Subprocess to close the underlying
584 * file descriptor. The child process may then receive SIGPIPE or get
585 * EPIPE errors on writes.
587 template <class Callback>
588 class ReadLinesCallback {
590 // Binds an FD to the client-provided FD+line callback
591 struct StreamSplitterCallback {
592 StreamSplitterCallback(Callback& cb, int fd) : cb_(cb), fd_(fd) { }
593 // The return value semantics are inverted vs StreamSplitter
594 bool operator()(StringPiece s) { return !cb_(fd_, s); }
598 typedef gen::StreamSplitter<StreamSplitterCallback> LineSplitter;
600 explicit ReadLinesCallback(
602 uint64_t maxLineLength = 0, // No line length limit by default
603 char delimiter = '\n',
604 uint64_t bufSize = 1024
605 ) : fdLineCb_(std::move(fdLineCb)),
606 maxLineLength_(maxLineLength),
607 delimiter_(delimiter),
610 bool operator()(int pfd, int cfd) {
611 // Make a splitter for this cfd if it doesn't already exist
612 auto it = fdToSplitter_.find(cfd);
613 auto& splitter = (it != fdToSplitter_.end()) ? it->second
614 : fdToSplitter_.emplace(cfd, LineSplitter(
615 delimiter_, StreamSplitterCallback(fdLineCb_, cfd), maxLineLength_
617 // Read as much as we can from this FD
620 ssize_t ret = readNoInt(pfd, buf, bufSize_);
621 if (ret == -1 && errno == EAGAIN) { // No more data for now
624 if (ret == 0) { // Reached end-of-file
625 splitter.flush(); // Ignore return since the file is over anyway
628 if (!splitter(StringPiece(buf, ret))) {
629 return true; // The callback told us to stop
636 const uint64_t maxLineLength_;
637 const char delimiter_;
638 const uint64_t bufSize_;
639 // We lazily make splitters for all cfds that get used.
640 std::unordered_map<int, LineSplitter> fdToSplitter_;
643 // Helper to enable template deduction
644 template <class Callback>
645 static ReadLinesCallback<Callback> readLinesCallback(
647 uint64_t maxLineLength = 0, // No line length limit by default
648 char delimiter = '\n',
649 uint64_t bufSize = 1024) {
650 return ReadLinesCallback<Callback>(
651 std::move(fdLineCb), maxLineLength, delimiter, bufSize
656 * communicate() callbacks can use this to temporarily enable/disable
657 * notifications (callbacks) for a pipe to/from the child. By default,
658 * all are enabled. Useful for "chatty" communication -- you want to
659 * disable write callbacks until you receive the expected message.
661 * Disabling a pipe does not free you from the requirement to consume all
662 * incoming data. Failing to do so will easily create deadlock bugs.
664 * Throws if the childFd is not known.
666 void enableNotifications(int childFd, bool enabled);
669 * Are notifications for one pipe to/from child enabled? Throws if the
670 * childFd is not known.
672 bool notificationsEnabled(int childFd) const;
675 //// The following methods are meant for the cases when communicate() is
676 //// not suitable. You should not need them when you call communicate(),
677 //// and, in fact, it is INHERENTLY UNSAFE to use closeParentFd() or
678 //// takeOwnershipOfPipes() from a communicate() callback.
682 * Close the parent file descriptor given a file descriptor in the child.
683 * DO NOT USE from communicate() callbacks; make them return true instead.
685 void closeParentFd(int childFd);
688 * Set all pipes from / to child to be non-blocking. communicate() does
691 void setAllNonBlocking();
694 * Get parent file descriptor corresponding to the given file descriptor
695 * in the child. Throws if childFd isn't a pipe (PIPE_IN / PIPE_OUT).
696 * Do not close() the returned file descriptor; use closeParentFd, above.
698 int parentFd(int childFd) const {
699 return pipes_[findByChildFd(childFd)].pipe.fd();
701 int stdin() const { return parentFd(0); }
702 int stdout() const { return parentFd(1); }
703 int stderr() const { return parentFd(2); }
706 * The child's pipes are logically separate from the process metadata
707 * (they may even be kept alive by the child's descendants). This call
708 * lets you manage the pipes' lifetime separetely from the lifetime of the
711 * After this call, the Subprocess instance will have no knowledge of
712 * these pipes, and the caller assumes responsibility for managing their
713 * lifetimes. Pro-tip: prefer to explicitly close() the pipes, since
714 * folly::File would otherwise silently suppress I/O errors.
716 * No, you may NOT call this from a communicate() callback.
719 ChildPipe(int fd, folly::File&& ppe) : childFd(fd), pipe(std::move(ppe)) {}
721 folly::File pipe; // Owns the parent FD
723 std::vector<ChildPipe> takeOwnershipOfPipes();
726 static const int RV_RUNNING = ProcessReturnCode::RV_RUNNING;
727 static const int RV_NOT_STARTED = ProcessReturnCode::RV_NOT_STARTED;
729 // spawn() sets up a pipe to read errors from the child,
730 // then calls spawnInternal() to do the bulk of the work. Once
731 // spawnInternal() returns it reads the error pipe to see if the child
732 // encountered any errors.
734 std::unique_ptr<const char*[]> argv,
735 const char* executable,
736 const Options& options,
737 const std::vector<std::string>* env);
739 std::unique_ptr<const char*[]> argv,
740 const char* executable,
742 const std::vector<std::string>* env,
745 // Actions to run in child.
746 // Note that this runs after vfork(), so tread lightly.
747 // Returns 0 on success, or an errno value on failure.
748 int prepareChild(const Options& options,
749 const sigset_t* sigmask,
750 const char* childDir) const;
751 int runChild(const char* executable, char** argv, char** env,
752 const Options& options) const;
755 * Read from the error pipe, and throw SubprocessSpawnError if the child
756 * failed before calling exec().
758 void readChildErrorPipe(int pfd, const char* executable);
760 // Returns an index into pipes_. Throws std::invalid_argument if not found.
761 size_t findByChildFd(const int childFd) const;
765 ProcessReturnCode returnCode_;
768 * Represents a pipe between this process, and the child process (or its
769 * descendant). To interact with these pipes, you can use communicate(),
770 * or use parentFd() and related methods, or separate them from the
771 * Subprocess instance entirely via takeOwnershipOfPipes().
773 struct Pipe : private boost::totally_ordered<Pipe> {
774 folly::File pipe; // Our end of the pipe, wrapped in a File to auto-close.
775 int childFd = -1; // Identifies the pipe: what FD is this in the child?
776 int direction = PIPE_IN; // one of PIPE_IN / PIPE_OUT
777 bool enabled = true; // Are notifications enabled in communicate()?
779 bool operator<(const Pipe& other) const {
780 return childFd < other.childFd;
782 bool operator==(const Pipe& other) const {
783 return childFd == other.childFd;
787 // Populated at process start according to fdActions, empty after
788 // takeOwnershipOfPipes(). Sorted by childFd. Can only have elements
789 // erased, but not inserted, after being populated.
791 // The number of pipes between parent and child is assumed to be small,
792 // so we're happy with a vector here, even if it means linear erase.
793 std::vector<Pipe> pipes_;
796 inline Subprocess::Options& Subprocess::Options::operator|=(
797 const Subprocess::Options& other) {
798 if (this == &other) return *this;
800 for (auto& p : other.fdActions_) {
801 fdActions_[p.first] = p.second;
803 closeOtherFds_ |= other.closeOtherFds_;
804 usePath_ |= other.usePath_;
805 processGroupLeader_ |= other.processGroupLeader_;
811 #endif /* FOLLY_SUBPROCESS_H_ */