Class Subprocess

java.lang.Object
org.javagi.base.ProxyInstance
org.gnome.gobject.TypeInstance
org.gnome.gobject.GObject
org.gnome.gio.Subprocess
All Implemented Interfaces:
Initable, Proxy
@Generated("org.javagi.JavaGI") public class Subprocess extends GObject implements Initable

GSubprocess allows the creation of and interaction with child processes.

Processes can be communicated with using standard GIO-style APIs (ie: InputStream, OutputStream). There are GIO-style APIs to wait for process termination (ie: cancellable and with an asynchronous variant).

There is an API to force a process to terminate, as well as a race-free API for sending UNIX signals to a subprocess.

One major advantage that GIO brings over the core GLib library is comprehensive API for asynchronous I/O, such OutputStream.spliceAsync(InputStream, Set, int, Cancellable, AsyncReadyCallback). This makes GSubprocess significantly more powerful and flexible than equivalent APIs in some other languages such as the subprocess.py included with Python. For example, using GSubprocess one could create two child processes, reading standard output from the first, processing it, and writing to the input stream of the second, all without blocking the main loop.

A powerful communicate(byte[], Cancellable, Out, Out) API is provided similar to the communicate() method of subprocess.py. This enables very easy interaction with a subprocess that has been opened with pipes.

GSubprocess defaults to tight control over the file descriptors open in the child process, avoiding dangling-FD issues that are caused by a simple fork()/exec(). The only open file descriptors in the spawned process are ones that were explicitly specified by the GSubprocess API (unless G_SUBPROCESS_FLAGS_INHERIT_FDS was specified).

GSubprocess will quickly reap all child processes as they exit, avoiding ‘zombie processes’ remaining around for long periods of time. wait_(Cancellable) can be used to wait for this to happen, but it will happen even without the call being explicitly made.

As a matter of principle, GSubprocess has no API that accepts shell-style space-separated strings. It will, however, match the typical shell behaviour of searching the PATH for executables that do not contain a directory separator in their name. By default, the PATH of the current process is used. You can specify G_SUBPROCESS_FLAGS_SEARCH_PATH_FROM_ENVP to use the PATH of the launcher environment instead.

GSubprocess attempts to have a very simple API for most uses (ie: spawning a subprocess with arguments and support for most typical kinds of input and output redirection). See Subprocess(). The SubprocessLauncher API is provided for more complicated cases (advanced types of redirection, environment variable manipulation, change of working directory, child setup functions, etc).

A typical use of GSubprocess will involve calling Subprocess(), followed by waitAsync(Cancellable, AsyncReadyCallback) or wait_(Cancellable). After the process exits, the status can be checked using functions such as getIfExited() (which are similar to the familiar WIFEXITED-style POSIX macros).

Note that as of GLib 2.82, creating a GSubprocess causes the signal SIGPIPE to be ignored for the remainder of the program. If you are writing a command-line utility that uses GSubprocess, you may need to take into account the fact that your program will not automatically be killed if it tries to write to stdout after it has been closed.

Since:
2.40

  • Constructor Details

    • Subprocess

      public Subprocess(MemorySegment address)
      Create a Subprocess instance for the provided memory address.
      Parameters:
      address - the memory address of the native object

    • Subprocess

      public Subprocess(@Nullable String @Nullable [] argv, Set<SubprocessFlags> flags) throws GErrorException

      Create a new process with the given flags and argument list.

      The argument list is expected to be null-terminated.

      Parameters:
      argv - commandline arguments for the subprocess
      flags - flags that define the behaviour of the subprocess
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • Subprocess

      public Subprocess(@Nullable String @Nullable [] argv, SubprocessFlags... flags) throws GErrorException

      Create a new process with the given flags and argument list.

      The argument list is expected to be null-terminated.

      Parameters:
      argv - commandline arguments for the subprocess
      flags - flags that define the behaviour of the subprocess
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • Subprocess

      public Subprocess()
      Create a new Subprocess.

  • Method Details

    • getType

      public static @Nullable Type getType()
      Get the GType of the Subprocess class.
      Returns:
      the GType

    • getMemoryLayout

      public static MemoryLayout getMemoryLayout()
      The memory layout of the native struct.
      Returns:
      the memory layout

    • asParent

      protected Subprocess asParent()
      Return this instance as if it were its parent type. Comparable to the Java super keyword, but ensures the parent typeclass is also used in native code.
      Overrides:
      asParent in class GObject
      Returns:
      the instance as if it were its parent type

    • communicate

      public boolean communicate(byte @Nullable [] stdinBuf, @Nullable Cancellable cancellable, @Nullable Out<byte[]> stdoutBuf, @Nullable Out<byte[]> stderrBuf) throws GErrorException

      Communicate with the subprocess until it terminates, and all input and output has been completed.

      If stdinBuf is given, the subprocess must have been created with SubprocessFlags.STDIN_PIPE. The given data is fed to the stdin of the subprocess and the pipe is closed (ie: EOF).

      At the same time (as not to cause blocking when dealing with large amounts of data), if SubprocessFlags.STDOUT_PIPE or SubprocessFlags.STDERR_PIPE were used, reads from those streams. The data that was read is returned in stdout and/or the stderr.

      If the subprocess was created with SubprocessFlags.STDOUT_PIPE, stdoutBuf will contain the data read from stdout. Otherwise, for subprocesses not created with SubprocessFlags.STDOUT_PIPE, stdoutBuf will be set to null. Similar provisions apply to stderrBuf and SubprocessFlags.STDERR_PIPE.

      As usual, any output variable may be given as null to ignore it.

      If you desire the stdout and stderr data to be interleaved, create the subprocess with SubprocessFlags.STDOUT_PIPE and SubprocessFlags.STDERR_MERGE. The merged result will be returned in stdoutBuf and stderrBuf will be set to null.

      In case of any error (including cancellation), false will be returned with error set. Some or all of the stdin data may have been written. Any stdout or stderr data that has been read will be discarded. None of the out variables (aside from error) will have been set to anything in particular and should not be inspected.

      In the case that true is returned, the subprocess has exited and the exit status inspection APIs (eg: g_subprocess_get_if_exited(), g_subprocess_get_exit_status()) may be used.

      You should not attempt to use any of the subprocess pipes after starting this function, since they may be left in strange states, even if the operation was cancelled. You should especially not attempt to interact with the pipes while the operation is in progress (either from another thread or if using the asynchronous version).

      Parameters:
      stdinBuf - data to send to the stdin of the subprocess, or null
      cancellable - a GCancellable
      stdoutBuf - data read from the subprocess stdout
      stderrBuf - data read from the subprocess stderr
      Returns:
      true if successful
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • communicateAsync

      public void communicateAsync(byte @Nullable [] stdinBuf, @Nullable Cancellable cancellable, @Nullable AsyncReadyCallback callback)
      Asynchronous version of g_subprocess_communicate(). Complete invocation with g_subprocess_communicate_finish().
      Parameters:
      stdinBuf - Input data, or null
      cancellable - Cancellable
      callback - Callback

    • communicateFinish

      public boolean communicateFinish(AsyncResult result, @Nullable Out<byte[]> stdoutBuf, @Nullable Out<byte[]> stderrBuf) throws GErrorException
      Complete an invocation of g_subprocess_communicate_async().
      Parameters:
      result - Result
      stdoutBuf - Return location for stdout data
      stderrBuf - Return location for stderr data
      Throws:
      GErrorException - see GError

    • communicateUtf8

      public boolean communicateUtf8(@Nullable String stdinBuf, @Nullable Cancellable cancellable, @Nullable Out<String> stdoutBuf, @Nullable Out<String> stderrBuf) throws GErrorException

      Like g_subprocess_communicate(), but validates the output of the process as UTF-8, and returns it as a regular NUL terminated string.

      On error, stdoutBuf and stderrBuf will be set to undefined values and should not be used.

      Parameters:
      stdinBuf - data to send to the stdin of the subprocess, or null
      cancellable - a GCancellable
      stdoutBuf - data read from the subprocess stdout
      stderrBuf - data read from the subprocess stderr
      Throws:
      GErrorException - see GError

    • communicateUtf8Async

      public void communicateUtf8Async(@Nullable String stdinBuf, @Nullable Cancellable cancellable, @Nullable AsyncReadyCallback callback)
      Asynchronous version of g_subprocess_communicate_utf8(). Complete invocation with g_subprocess_communicate_utf8_finish().
      Parameters:
      stdinBuf - Input data, or null
      cancellable - Cancellable
      callback - Callback

    • communicateUtf8Finish

      public boolean communicateUtf8Finish(AsyncResult result, @Nullable Out<String> stdoutBuf, @Nullable Out<String> stderrBuf) throws GErrorException
      Complete an invocation of g_subprocess_communicate_utf8_async().
      Parameters:
      result - Result
      stdoutBuf - Return location for stdout data
      stderrBuf - Return location for stderr data
      Throws:
      GErrorException - see GError

    • forceExit

      public void forceExit()

      Use an operating-system specific method to attempt an immediate, forceful termination of the process. There is no mechanism to determine whether or not the request itself was successful; however, you can use g_subprocess_wait() to monitor the status of the process after calling this function.

      On Unix, this function sends SIGKILL.

      Since:
      2.40

    • getExitStatus

      public int getExitStatus()

      Check the exit status of the subprocess, given that it exited normally. This is the value passed to the exit() system call or the return value from main.

      This is equivalent to the system WEXITSTATUS macro.

      It is an error to call this function before g_subprocess_wait() and unless g_subprocess_get_if_exited() returned true.

      Returns:
      the exit status
      Since:
      2.40

    • getIdentifier

      public @Nullable String getIdentifier()
      On UNIX, returns the process ID as a decimal string. On Windows, returns the result of GetProcessId() also as a string. If the subprocess has terminated, this will return null.
      Returns:
      the subprocess identifier, or null if the subprocess has terminated
      Since:
      2.40

    • getIfExited

      public boolean getIfExited()

      Check if the given subprocess exited normally (ie: by way of exit() or return from main()).

      This is equivalent to the system WIFEXITED macro.

      It is an error to call this function before g_subprocess_wait() has returned.

      Returns:
      true if the case of a normal exit
      Since:
      2.40

    • getIfSignaled

      public boolean getIfSignaled()

      Check if the given subprocess terminated in response to a signal.

      This is equivalent to the system WIFSIGNALED macro.

      It is an error to call this function before g_subprocess_wait() has returned.

      Returns:
      true if the case of termination due to a signal
      Since:
      2.40

    • getStatus

      public int getStatus()

      Gets the raw status code of the process, as from waitpid().

      This value has no particular meaning, but it can be used with the macros defined by the system headers such as WIFEXITED. It can also be used with g_spawn_check_wait_status().

      It is more likely that you want to use g_subprocess_get_if_exited() followed by g_subprocess_get_exit_status().

      It is an error to call this function before g_subprocess_wait() has returned.

      Returns:
      the (meaningless) waitpid() exit status from the kernel
      Since:
      2.40

    • getStderrPipe

      public @Nullable InputStream getStderrPipe()

      Gets the GInputStream from which to read the stderr output of subprocess.

      The process must have been created with SubprocessFlags.STDERR_PIPE, otherwise null will be returned.

      Returns:
      the stderr pipe
      Since:
      2.40

    • getStdinPipe

      public @Nullable OutputStream getStdinPipe()

      Gets the GOutputStream that you can write to in order to give data to the stdin of subprocess.

      The process must have been created with SubprocessFlags.STDIN_PIPE and not SubprocessFlags.STDIN_INHERIT, otherwise null will be returned.

      Returns:
      the stdout pipe
      Since:
      2.40

    • getStdoutPipe

      public @Nullable InputStream getStdoutPipe()

      Gets the GInputStream from which to read the stdout output of subprocess.

      The process must have been created with SubprocessFlags.STDOUT_PIPE, otherwise null will be returned.

      Returns:
      the stdout pipe
      Since:
      2.40

    • getSuccessful

      public boolean getSuccessful()

      Checks if the process was "successful". A process is considered successful if it exited cleanly with an exit status of 0, either by way of the exit() system call or return from main().

      It is an error to call this function before g_subprocess_wait() has returned.

      Returns:
      true if the process exited cleanly with a exit status of 0
      Since:
      2.40

    • getTermSig

      public int getTermSig()

      Get the signal number that caused the subprocess to terminate, given that it terminated due to a signal.

      This is equivalent to the system WTERMSIG macro.

      It is an error to call this function before g_subprocess_wait() and unless g_subprocess_get_if_signaled() returned true.

      Returns:
      the signal causing termination
      Since:
      2.40

    • sendSignal

      public void sendSignal(int signalNum)

      Sends the UNIX signal signalNum to the subprocess, if it is still running.

      This API is race-free. If the subprocess has terminated, it will not be signalled.

      This API is not available on Windows.

      Parameters:
      signalNum - the signal number to send
      Since:
      2.40

    • wait_

      public boolean wait_(@Nullable Cancellable cancellable) throws GErrorException

      Synchronously wait for the subprocess to terminate.

      After the process terminates you can query its exit status with functions such as g_subprocess_get_if_exited() and g_subprocess_get_exit_status().

      This function does not fail in the case of the subprocess having abnormal termination. See g_subprocess_wait_check() for that.

      Cancelling cancellable doesn't kill the subprocess. Call g_subprocess_force_exit() if it is desirable.

      Parameters:
      cancellable - a GCancellable
      Returns:
      true on success, false if cancellable was cancelled
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • waitAsync

      public void waitAsync(@Nullable Cancellable cancellable, @Nullable AsyncReadyCallback callback)

      Wait for the subprocess to terminate.

      This is the asynchronous version of g_subprocess_wait().

      Parameters:
      cancellable - a GCancellable, or null
      callback - a GAsyncReadyCallback to call when the operation is complete
      Since:
      2.40

    • waitCheck

      public boolean waitCheck(@Nullable Cancellable cancellable) throws GErrorException
      Combines g_subprocess_wait() with g_spawn_check_wait_status().
      Parameters:
      cancellable - a GCancellable
      Returns:
      true on success, false if process exited abnormally, or cancellable was cancelled
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • waitCheckAsync

      public void waitCheckAsync(@Nullable Cancellable cancellable, @Nullable AsyncReadyCallback callback)

      Combines g_subprocess_wait_async() with g_spawn_check_wait_status().

      This is the asynchronous version of g_subprocess_wait_check().

      Parameters:
      cancellable - a GCancellable, or null
      callback - a GAsyncReadyCallback to call when the operation is complete
      Since:
      2.40

    • waitCheckFinish

      public boolean waitCheckFinish(AsyncResult result) throws GErrorException
      Collects the result of a previous call to g_subprocess_wait_check_async().
      Parameters:
      result - the GAsyncResult passed to your GAsyncReadyCallback
      Returns:
      true if successful, or false with error set
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • waitFinish

      public boolean waitFinish(AsyncResult result) throws GErrorException
      Collects the result of a previous call to g_subprocess_wait_async().
      Parameters:
      result - the GAsyncResult passed to your GAsyncReadyCallback
      Returns:
      true if successful, or false with error set
      Throws:
      GErrorException - see GError
      Since:
      2.40

    • builder

      public static Subprocess.Builder<? extends Subprocess.Builder> builder()
      A Subprocess.Builder object constructs a Subprocess with the specified properties. Use the various set...() methods to set properties, and finish construction with Subprocess.Builder.build().
      Returns:
      the builder object