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.
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;
129 // Subprocess starts in the constructor, so this state designates only
130 // default-initialized or moved-out ProcessReturnCodes.
137 // Default-initialized for convenience. Subprocess::returnCode() will
138 // never produce this value.
139 ProcessReturnCode() : ProcessReturnCode(RV_NOT_STARTED) {}
141 // Trivially copyable
142 ProcessReturnCode(const ProcessReturnCode& p) = default;
143 ProcessReturnCode& operator=(const ProcessReturnCode& p) = default;
144 // Non-default move: In order for Subprocess to be movable, the "moved
145 // out" state must not be "running", or ~Subprocess() will abort.
146 ProcessReturnCode(ProcessReturnCode&& p) noexcept;
147 ProcessReturnCode& operator=(ProcessReturnCode&& p) noexcept;
150 * Process state. One of:
151 * NOT_STARTED: process hasn't been started successfully
152 * RUNNING: process is currently running
153 * EXITED: process exited (successfully or not)
154 * KILLED: process was killed by a signal.
159 * Helper wrappers around state().
161 bool notStarted() const { return state() == NOT_STARTED; }
162 bool running() const { return state() == RUNNING; }
163 bool exited() const { return state() == EXITED; }
164 bool killed() const { return state() == KILLED; }
167 * Exit status. Only valid if state() == EXITED; throws otherwise.
169 int exitStatus() const;
172 * Signal that caused the process's termination. Only valid if
173 * state() == KILLED; throws otherwise.
175 int killSignal() const;
178 * Was a core file generated? Only valid if state() == KILLED; throws
181 bool coreDumped() const;
184 * String representation; one of
187 * "exited with status <status>"
188 * "killed by signal <signal>"
189 * "killed by signal <signal> (core dumped)"
191 std::string str() const;
194 * Helper function to enforce a precondition based on this.
195 * Throws std::logic_error if in an unexpected state.
197 void enforce(State state) const;
199 explicit ProcessReturnCode(int rv) : rawStatus_(rv) { }
200 static constexpr int RV_NOT_STARTED = -2;
201 static constexpr int RV_RUNNING = -1;
207 * Base exception thrown by the Subprocess methods.
209 class SubprocessError : public std::exception {};
212 * Exception thrown by *Checked methods of Subprocess.
214 class CalledProcessError : public SubprocessError {
216 explicit CalledProcessError(ProcessReturnCode rc);
217 ~CalledProcessError() throw() = default;
218 const char* what() const throw() override { return what_.c_str(); }
219 ProcessReturnCode returnCode() const { return returnCode_; }
221 ProcessReturnCode returnCode_;
226 * Exception thrown if the subprocess cannot be started.
228 class SubprocessSpawnError : public SubprocessError {
230 SubprocessSpawnError(const char* executable, int errCode, int errnoValue);
231 ~SubprocessSpawnError() throw() = default;
232 const char* what() const throw() override { return what_.c_str(); }
233 int errnoValue() const { return errnoValue_; }
245 static const int CLOSE = -1;
246 static const int PIPE = -2;
247 static const int PIPE_IN = -3;
248 static const int PIPE_OUT = -4;
251 * See Subprocess::Options::dangerousPostForkPreExecCallback() for usage.
252 * Every derived class should include the following warning:
254 * DANGER: This class runs after fork in a child processes. Be fast, the
255 * parent thread is waiting, but remember that other parent threads are
256 * running and may mutate your state. Avoid mutating any data belonging to
257 * the parent. Avoid interacting with non-POD data that originated in the
258 * parent. Avoid any libraries that may internally reference non-POD data.
259 * Especially beware parent mutexes -- for example, glog's LOG() uses one.
261 struct DangerousPostForkPreExecCallback {
262 virtual ~DangerousPostForkPreExecCallback() {}
263 // This must return 0 on success, or an `errno` error code.
264 virtual int operator()() = 0;
268 * Class representing various options: file descriptor behavior, and
269 * whether to use $PATH for searching for the executable,
271 * By default, we don't use $PATH, file descriptors are closed if
272 * the close-on-exec flag is set (fcntl FD_CLOEXEC) and inherited
275 class Options : private boost::orable<Options> {
276 friend class Subprocess;
278 Options() {} // E.g. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58328
281 * Change action for file descriptor fd.
283 * "action" may be another file descriptor number (dup2()ed before the
284 * child execs), or one of CLOSE, PIPE_IN, and PIPE_OUT.
286 * CLOSE: close the file descriptor in the child
287 * PIPE_IN: open a pipe *from* the child
288 * PIPE_OUT: open a pipe *to* the child
290 * PIPE is a shortcut; same as PIPE_IN for stdin (fd 0), same as
291 * PIPE_OUT for stdout (fd 1) or stderr (fd 2), and an error for
292 * other file descriptors.
294 Options& fd(int fd, int action);
297 * Shortcut to change the action for standard input.
299 Options& stdin(int action) { return fd(STDIN_FILENO, action); }
302 * Shortcut to change the action for standard output.
304 Options& stdout(int action) { return fd(STDOUT_FILENO, action); }
307 * Shortcut to change the action for standard error.
308 * Note that stderr(1) will redirect the standard error to the same
309 * file descriptor as standard output; the equivalent of bash's "2>&1"
311 Options& stderr(int action) { return fd(STDERR_FILENO, action); }
313 Options& pipeStdin() { return fd(STDIN_FILENO, PIPE_IN); }
314 Options& pipeStdout() { return fd(STDOUT_FILENO, PIPE_OUT); }
315 Options& pipeStderr() { return fd(STDERR_FILENO, PIPE_OUT); }
318 * Close all other fds (other than standard input, output, error,
319 * and file descriptors explicitly specified with fd()).
321 * This is potentially slow; it's generally a better idea to
322 * set the close-on-exec flag on all file descriptors that shouldn't
323 * be inherited by the child.
325 * Even with this option set, standard input, output, and error are
326 * not closed; use stdin(CLOSE), stdout(CLOSE), stderr(CLOSE) if you
329 Options& closeOtherFds() { closeOtherFds_ = true; return *this; }
332 * Use the search path ($PATH) when searching for the executable.
334 Options& usePath() { usePath_ = true; return *this; }
337 * Change the child's working directory, after the vfork.
339 Options& chdir(const std::string& dir) { childDir_ = dir; return *this; }
343 * Child will receive a signal when the parent exits.
345 Options& parentDeathSignal(int sig) {
346 parentDeathSignal_ = sig;
352 * Child will be made a process group leader when it starts. Upside: one
353 * can reliably all its kill non-daemonizing descendants. Downside: the
354 * child will not receive Ctrl-C etc during interactive use.
356 Options& processGroupLeader() {
357 processGroupLeader_ = true;
362 * *** READ THIS WHOLE DOCBLOCK BEFORE USING ***
364 * Run this callback in the child after the fork, just before the
365 * exec(), and after the child's state has been completely set up:
366 * - signal handlers have been reset to default handling and unblocked
367 * - the working directory was set
368 * - closed any file descriptors specified via Options()
369 * - set child process flags (see code)
371 * This is EXTREMELY DANGEROUS. For example, this innocuous-looking code
372 * can cause a fraction of your Subprocess launches to hang forever:
374 * LOG(INFO) << "Hello from the child";
376 * The reason is that glog has an internal mutex. If your fork() happens
377 * when the parent has the mutex locked, the child will wait forever.
381 * - Be quick -- the parent thread is blocked until you exit.
382 * - Remember that other parent threads are running, and may mutate your
384 * - Avoid mutating any data belonging to the parent.
385 * - Avoid interacting with non-POD data that came from the parent.
386 * - Avoid any libraries that may internally reference non-POD state.
387 * - Especially beware parent mutexes, e.g. LOG() uses a global mutex.
388 * - Avoid invoking the parent's destructors (you can accidentally
389 * delete files, terminate network connections, etc).
390 * - Read http://ewontfix.com/7/
392 Options& dangerousPostForkPreExecCallback(
393 DangerousPostForkPreExecCallback* cob) {
394 dangerousPostForkPreExecCallback_ = cob;
399 * Helpful way to combine Options.
401 Options& operator|=(const Options& other);
404 typedef boost::container::flat_map<int, int> FdMap;
406 bool closeOtherFds_{false};
407 bool usePath_{false};
408 std::string childDir_; // "" keeps the parent's working directory
410 int parentDeathSignal_{0};
412 bool processGroupLeader_{false};
413 DangerousPostForkPreExecCallback*
414 dangerousPostForkPreExecCallback_{nullptr};
417 static Options pipeStdin() { return Options().stdin(PIPE); }
418 static Options pipeStdout() { return Options().stdout(PIPE); }
419 static Options pipeStderr() { return Options().stderr(PIPE); }
421 // Non-copiable, but movable
422 Subprocess(const Subprocess&) = delete;
423 Subprocess& operator=(const Subprocess&) = delete;
424 Subprocess(Subprocess&&) = default;
425 Subprocess& operator=(Subprocess&&) = default;
428 * Create a subprocess from the given arguments. argv[0] must be listed.
429 * If not-null, executable must be the actual executable
430 * being used (otherwise it's the same as argv[0]).
432 * If env is not-null, it must contain name=value strings to be used
433 * as the child's environment; otherwise, we inherit the environment
434 * from the parent. env must be null if options.usePath is set.
437 const std::vector<std::string>& argv,
438 const Options& options = Options(),
439 const char* executable = nullptr,
440 const std::vector<std::string>* env = nullptr);
444 * Create a subprocess run as a shell command (as shell -c 'command')
446 * The shell to use is taken from the environment variable $SHELL,
447 * or /bin/sh if $SHELL is unset.
450 const std::string& cmd,
451 const Options& options = Options(),
452 const std::vector<std::string>* env = nullptr);
455 //// The methods below only manipulate the process state, and do not
456 //// affect its communication pipes.
460 * Return the child's pid, or -1 if the child wasn't successfully spawned
461 * or has already been wait()ed upon.
466 * Return the child's status (as per wait()) if the process has already
467 * been waited on, -1 if the process is still running, or -2 if the
468 * process hasn't been successfully started. NOTE that this does not call
469 * waitpid() or Subprocess::poll(), but simply returns the status stored
470 * in the Subprocess object.
472 ProcessReturnCode returnCode() const { return returnCode_; }
475 * Poll the child's status and return it. Return the exit status if the
476 * subprocess had quit, or RUNNING otherwise. Throws an std::logic_error
477 * if called on a Subprocess whose status is no longer RUNNING. No other
478 * exceptions are possible. Aborts on egregious violations of contract,
479 * e.g. if you wait for the underlying process without going through this
480 * Subprocess instance.
482 ProcessReturnCode poll();
485 * Poll the child's status. If the process is still running, return false.
486 * Otherwise, return true if the process exited with status 0 (success),
487 * or throw CalledProcessError if the process exited with a non-zero status.
492 * Wait for the process to terminate and return its status. Like poll(),
493 * the only exception this can throw is std::logic_error if you call this
494 * on a Subprocess whose status is RUNNING. Aborts on egregious
495 * violations of contract, like an out-of-band waitpid(p.pid(), 0, 0).
497 ProcessReturnCode wait();
500 * Wait for the process to terminate, throw if unsuccessful.
505 * Send a signal to the child. Shortcuts for the commonly used Unix
508 void sendSignal(int signal);
509 void terminate() { sendSignal(SIGTERM); }
510 void kill() { sendSignal(SIGKILL); }
513 //// The methods below only affect the process's communication pipes, but
514 //// not its return code or state (they do not poll() or wait()).
518 * Communicate with the child until all pipes to/from the child are closed.
520 * The input buffer is written to the process' stdin pipe, and data is read
521 * from the stdout and stderr pipes. Non-blocking I/O is performed on all
522 * pipes simultaneously to avoid deadlocks.
524 * The stdin pipe will be closed after the full input buffer has been written.
525 * An error will be thrown if a non-empty input buffer is supplied but stdin
526 * was not configured as a pipe.
528 * Returns a pair of buffers containing the data read from stdout and stderr.
529 * If stdout or stderr is not a pipe, an empty IOBuf queue will be returned
530 * for the respective buffer.
532 * Note that communicate() and communicateIOBuf() both return when all
533 * pipes to/from the child are closed; the child might stay alive after
534 * that, so you must still wait().
536 * communicateIOBuf() uses IOBufQueue for buffering (which has the
537 * advantage that it won't try to allocate all data at once), but it does
538 * store the subprocess's entire output in memory before returning.
540 * communicate() uses strings for simplicity.
542 std::pair<IOBufQueue, IOBufQueue> communicateIOBuf(
543 IOBufQueue input = IOBufQueue());
545 std::pair<std::string, std::string> communicate(
546 StringPiece input = StringPiece());
549 * Communicate with the child until all pipes to/from the child are closed.
553 * readCallback(pfd, cfd) will be called whenever there's data available
554 * on any pipe *from* the child (PIPE_OUT). pfd is the file descriptor
555 * in the parent (that you use to read from); cfd is the file descriptor
556 * in the child (used for identifying the stream; 1 = child's standard
557 * output, 2 = child's standard error, etc)
559 * writeCallback(pfd, cfd) will be called whenever a pipe *to* the child is
560 * writable (PIPE_IN). pfd is the file descriptor in the parent (that you
561 * use to write to); cfd is the file descriptor in the child (used for
562 * identifying the stream; 0 = child's standard input, etc)
564 * The read and write callbacks must read from / write to pfd and return
565 * false during normal operation. Return true to tell communicate() to
566 * close the pipe. For readCallback, this might send SIGPIPE to the
567 * child, or make its writes fail with EPIPE, so you should generally
568 * avoid returning true unless you've reached end-of-file.
570 * communicate() returns when all pipes to/from the child are closed; the
571 * child might stay alive after that, so you must still wait().
572 * Conversely, the child may quit long before its pipes are closed, since
573 * its descendants can keep them alive forever.
575 * Most users won't need to use this callback version; the simpler version
576 * of communicate (which buffers data in memory) will probably work fine.
578 * == Things you must get correct ==
580 * 1) You MUST consume all data passed to readCallback (or return true to
581 * close the pipe). Similarly, you MUST write to a writable pipe (or
582 * return true to close the pipe). To do otherwise is an error that can
583 * result in a deadlock. You must do this even for pipes you are not
586 * 2) pfd is nonblocking, so be prepared for read() / write() to return -1
587 * and set errno to EAGAIN (in which case you should return false). Use
588 * readNoInt() from FileUtil.h to handle interrupted reads for you.
590 * 3) Your callbacks MUST NOT call any of the Subprocess methods that
591 * manipulate the pipe FDs. Check the docblocks, but, for example,
592 * neither closeParentFd (return true instead) nor takeOwnershipOfPipes
593 * are safe. Stick to reading/writing from pfd, as appropriate.
597 * 1) See ReadLinesCallback for an easy way to consume the child's output
598 * streams line-by-line (or tokenized by another delimiter).
600 * 2) "Wait until the descendants close the pipes" is usually the behavior
601 * you want, since the descendants may have something to say even if the
602 * immediate child is dead. If you need to be able to force-close all
603 * parent FDs, communicate() will NOT work for you. Do it your own way by
604 * using takeOwnershipOfPipes().
606 * Why not? You can return "true" from your callbacks to sever active
607 * pipes, but inactive ones can remain open indefinitely. It is
608 * impossible to safely close inactive pipes while another thread is
609 * blocked in communicate(). This is BY DESIGN. Racing communicate()'s
610 * read/write callbacks can result in wrong I/O and data corruption. This
611 * class would need internal synchronization and timeouts, a poor and
612 * expensive implementation choice, in order to make closeParentFd()
615 typedef std::function<bool(int, int)> FdCallback;
616 void communicate(FdCallback readCallback, FdCallback writeCallback);
619 * A readCallback for Subprocess::communicate() that helps you consume
620 * lines (or other delimited pieces) from your subprocess's file
621 * descriptors. Use the readLinesCallback() helper to get template
622 * deduction. For example:
624 * auto read_cb = Subprocess::readLinesCallback(
625 * [](int fd, folly::StringPiece s) {
626 * std::cout << fd << " said: " << s;
627 * return false; // Keep reading from the child
630 * subprocess.communicate(
631 * // ReadLinesCallback contains StreamSplitter contains IOBuf, making
632 * // it noncopyable, whereas std::function must be copyable. So, we
633 * // keep the callback in a local, and instead pass a reference.
635 * [](int pdf, int cfd){ return true; } // Don't write to the child
638 * If a file line exceeds maxLineLength, your callback will get some
639 * initial chunks of maxLineLength with no trailing delimiters. The final
640 * chunk of a line is delimiter-terminated iff the delimiter was present
641 * in the input. In particular, the last line in a file always lacks a
642 * delimiter -- so if a file ends on a delimiter, the final line is empty.
644 * Like a regular communicate() callback, your fdLineCb() normally returns
645 * false. It may return true to tell Subprocess to close the underlying
646 * file descriptor. The child process may then receive SIGPIPE or get
647 * EPIPE errors on writes.
649 template <class Callback>
650 class ReadLinesCallback {
652 // Binds an FD to the client-provided FD+line callback
653 struct StreamSplitterCallback {
654 StreamSplitterCallback(Callback& cb, int fd) : cb_(cb), fd_(fd) { }
655 // The return value semantics are inverted vs StreamSplitter
656 bool operator()(StringPiece s) { return !cb_(fd_, s); }
660 typedef gen::StreamSplitter<StreamSplitterCallback> LineSplitter;
662 explicit ReadLinesCallback(
664 uint64_t maxLineLength = 0, // No line length limit by default
665 char delimiter = '\n',
666 uint64_t bufSize = 1024
667 ) : fdLineCb_(std::move(fdLineCb)),
668 maxLineLength_(maxLineLength),
669 delimiter_(delimiter),
672 bool operator()(int pfd, int cfd) {
673 // Make a splitter for this cfd if it doesn't already exist
674 auto it = fdToSplitter_.find(cfd);
675 auto& splitter = (it != fdToSplitter_.end()) ? it->second
676 : fdToSplitter_.emplace(cfd, LineSplitter(
677 delimiter_, StreamSplitterCallback(fdLineCb_, cfd), maxLineLength_
679 // Read as much as we can from this FD
682 ssize_t ret = readNoInt(pfd, buf, bufSize_);
683 if (ret == -1 && errno == EAGAIN) { // No more data for now
686 if (ret == 0) { // Reached end-of-file
687 splitter.flush(); // Ignore return since the file is over anyway
690 if (!splitter(StringPiece(buf, ret))) {
691 return true; // The callback told us to stop
698 const uint64_t maxLineLength_;
699 const char delimiter_;
700 const uint64_t bufSize_;
701 // We lazily make splitters for all cfds that get used.
702 std::unordered_map<int, LineSplitter> fdToSplitter_;
705 // Helper to enable template deduction
706 template <class Callback>
707 static ReadLinesCallback<Callback> readLinesCallback(
709 uint64_t maxLineLength = 0, // No line length limit by default
710 char delimiter = '\n',
711 uint64_t bufSize = 1024) {
712 return ReadLinesCallback<Callback>(
713 std::move(fdLineCb), maxLineLength, delimiter, bufSize
718 * communicate() callbacks can use this to temporarily enable/disable
719 * notifications (callbacks) for a pipe to/from the child. By default,
720 * all are enabled. Useful for "chatty" communication -- you want to
721 * disable write callbacks until you receive the expected message.
723 * Disabling a pipe does not free you from the requirement to consume all
724 * incoming data. Failing to do so will easily create deadlock bugs.
726 * Throws if the childFd is not known.
728 void enableNotifications(int childFd, bool enabled);
731 * Are notifications for one pipe to/from child enabled? Throws if the
732 * childFd is not known.
734 bool notificationsEnabled(int childFd) const;
737 //// The following methods are meant for the cases when communicate() is
738 //// not suitable. You should not need them when you call communicate(),
739 //// and, in fact, it is INHERENTLY UNSAFE to use closeParentFd() or
740 //// takeOwnershipOfPipes() from a communicate() callback.
744 * Close the parent file descriptor given a file descriptor in the child.
745 * DO NOT USE from communicate() callbacks; make them return true instead.
747 void closeParentFd(int childFd);
750 * Set all pipes from / to child to be non-blocking. communicate() does
753 void setAllNonBlocking();
756 * Get parent file descriptor corresponding to the given file descriptor
757 * in the child. Throws if childFd isn't a pipe (PIPE_IN / PIPE_OUT).
758 * Do not close() the returned file descriptor; use closeParentFd, above.
760 int parentFd(int childFd) const {
761 return pipes_[findByChildFd(childFd)].pipe.fd();
763 int stdin() const { return parentFd(0); }
764 int stdout() const { return parentFd(1); }
765 int stderr() const { return parentFd(2); }
768 * The child's pipes are logically separate from the process metadata
769 * (they may even be kept alive by the child's descendants). This call
770 * lets you manage the pipes' lifetime separetely from the lifetime of the
773 * After this call, the Subprocess instance will have no knowledge of
774 * these pipes, and the caller assumes responsibility for managing their
775 * lifetimes. Pro-tip: prefer to explicitly close() the pipes, since
776 * folly::File would otherwise silently suppress I/O errors.
778 * No, you may NOT call this from a communicate() callback.
781 ChildPipe(int fd, folly::File&& ppe) : childFd(fd), pipe(std::move(ppe)) {}
783 folly::File pipe; // Owns the parent FD
785 std::vector<ChildPipe> takeOwnershipOfPipes();
788 static const int RV_RUNNING = ProcessReturnCode::RV_RUNNING;
789 static const int RV_NOT_STARTED = ProcessReturnCode::RV_NOT_STARTED;
791 // spawn() sets up a pipe to read errors from the child,
792 // then calls spawnInternal() to do the bulk of the work. Once
793 // spawnInternal() returns it reads the error pipe to see if the child
794 // encountered any errors.
796 std::unique_ptr<const char*[]> argv,
797 const char* executable,
798 const Options& options,
799 const std::vector<std::string>* env);
801 std::unique_ptr<const char*[]> argv,
802 const char* executable,
804 const std::vector<std::string>* env,
807 // Actions to run in child.
808 // Note that this runs after vfork(), so tread lightly.
809 // Returns 0 on success, or an errno value on failure.
810 int prepareChild(const Options& options,
811 const sigset_t* sigmask,
812 const char* childDir) const;
813 int runChild(const char* executable, char** argv, char** env,
814 const Options& options) const;
817 * Read from the error pipe, and throw SubprocessSpawnError if the child
818 * failed before calling exec().
820 void readChildErrorPipe(int pfd, const char* executable);
822 // Returns an index into pipes_. Throws std::invalid_argument if not found.
823 size_t findByChildFd(const int childFd) const;
827 ProcessReturnCode returnCode_;
830 * Represents a pipe between this process, and the child process (or its
831 * descendant). To interact with these pipes, you can use communicate(),
832 * or use parentFd() and related methods, or separate them from the
833 * Subprocess instance entirely via takeOwnershipOfPipes().
835 struct Pipe : private boost::totally_ordered<Pipe> {
836 folly::File pipe; // Our end of the pipe, wrapped in a File to auto-close.
837 int childFd = -1; // Identifies the pipe: what FD is this in the child?
838 int direction = PIPE_IN; // one of PIPE_IN / PIPE_OUT
839 bool enabled = true; // Are notifications enabled in communicate()?
841 bool operator<(const Pipe& other) const {
842 return childFd < other.childFd;
844 bool operator==(const Pipe& other) const {
845 return childFd == other.childFd;
849 // Populated at process start according to fdActions, empty after
850 // takeOwnershipOfPipes(). Sorted by childFd. Can only have elements
851 // erased, but not inserted, after being populated.
853 // The number of pipes between parent and child is assumed to be small,
854 // so we're happy with a vector here, even if it means linear erase.
855 std::vector<Pipe> pipes_;
858 inline Subprocess::Options& Subprocess::Options::operator|=(
859 const Subprocess::Options& other) {
860 if (this == &other) return *this;
862 for (auto& p : other.fdActions_) {
863 fdActions_[p.first] = p.second;
865 closeOtherFds_ |= other.closeOtherFds_;
866 usePath_ |= other.usePath_;
867 processGroupLeader_ |= other.processGroupLeader_;
873 #endif /* FOLLY_SUBPROCESS_H_ */