Processes
(ply-system.h)

PID getCurrentProcessId()

Returns the operating system's process ID for the current process. See also getCurrentThreadId.

String getCurrentExecutablePath()

Returns the path to the executable file for the current process.

String getEnvironmentVariable(StringView name)

Returns the value of the environment variable specified by name. Returns an empty string if the variable is unset.

Subprocess

The Subprocess class represents a child process. You can spawn processes, redirect their I/O and wait for them to complete. Not supported on iOS.

Owned<Subprocess> process = Subprocess::execShellCommand("ls -la", "/home/user",
                                                         Subprocess::Output::openMerged());
String output = readAllRemainingData(process->getStdOutReader());
s32 exitCode = process->join();

static Owned<Subprocess> Subprocess::exec(StringView exePath, ArrayView<const StringView> args, StringView initialDir, const Subprocess::Output& output, const Subprocess::Input& input, const Subprocess::Options& options)

Spawns a new process. exePath is the path to the executable. args is an array of command-line arguments. initialDir is the working directory for the new process.

Pass any of the following values to output:

Output::ignore()	Discards the output.
Output::inherit()	Inherits the parent process's stdout/stderr.
Output::openSeparate()	Opens separate pipes to read from stdout/stderr.
Output::openMerged()	Opens a single pipe to read from both stdout and stderr.
Output::openStdOutOnly()	Opens a pipe to read from stdout and ignores stderr.

Pass any of the following values to input:

Input::ignore()	Sends no input.
Input::inherit()	Inherits the parent process's stdin.
Input::open()	Opens a pipe to write to stdin.

Subprocess::Options has the following members:

terminateProcessTree

If true and the subprocess spawns its own subprocesses, calling terminate() terminates the entire subprocess tree. Default is false.

Note that on POSIX platforms, enabling terminateProcessTree places the subprocess tree in a separate process group. As such, terminal-generated signals received by the parent process (such as SIGINT generated by Ctrl-C) will no longer be automatically received by the subprocess tree.

static Owned<Subprocess> Subprocess::execShellCommand(StringView shellCommand, StringView initialDir, const Subprocess::Output& output, const Subprocess::Input& input, const Subprocess::Options& options)

Spawns a new process by passing shellCommand to the platform's default command interpreter. The output, input and options parameters behave the same as in exec().

Pipe* Subprocess::getStdInWriter() const

Returns a pipe that writes to the subprocess's stdin, or nullptr if stdin wasn't opened.

Pipe* Subprocess::getStdOutReader() const

Returns a pipe that reads the subprocess's stdout, or nullptr if stdout wasn't opened.

Pipe* Subprocess::getStdErrReader() const

Returns a pipe that reads the subprocess's stderr, or nullptr if stderr wasn't opened.

s32 Subprocess::join()

Waits for the subprocess to exit and returns its exit code. Does not wait for any descendant processes spawned by the subprocess.

JoinResult Subprocess::joinWithTimeout(s32 timeoutMillis)

Waits for the subprocess to exit with a timeout. A negative timeout value waits indefinitely. Does not wait for any descendant processes that may have been spawned by the subprocess. JoinResult has the following members:

bool joined	true if the subprocess exited; false if the timeout was reached.
s32 exitCode	The exit code, if the subprocess exited.

bool Subprocess::terminate()

Forcibly terminates the subprocess. If the subprocess hasn't been joined, and Options::terminateProcessTree was enabled when the process was created, then its subprocess tree is also terminated. If terminate() is called while another thread is waiting on a join function, the waiting thread is released.

The terminated subprocess closes its standard I/O pipes when it exits. If terminate() is called while another thread is waiting inside a read() from one of those pipes, the waiting thread is released.