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GSubprocess allows the creation of and interaction with child processes.
Processes can be communicated with using standard GIO-style APIs (ie: GInputStream, GOutputStream). 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
g_output_stream_splice_async(). 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 g_subprocess_communicate() API is provided similar to the
communicate()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. g_subprocess_wait() 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.
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 g_subprocess_new(). The
GSubprocessLauncher 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
g_subprocess_new(), followed by g_subprocess_wait_async() or
g_subprocess_wait(). After the process exits, the status can be
checked using functions such as g_subprocess_get_if_exited() (which
are similar to the familiar WIFEXITED-style POSIX macros).
GSubprocess * g_subprocess_new (GSubprocessFlags flags,GError **error,const gchar *argv0,...);
Create a new process with the given flags and varargs argument
list. By default, matching the g_spawn_async() defaults, the
child's stdin will be set to the system null device, and
stdout/stderr will be inherited from the parent. You can use
flags
to control this behavior.
The argument list must be terminated with NULL.
[skip]
Since: 2.40
GSubprocess * g_subprocess_newv (const gchar * const *argv,GSubprocessFlags flags,GError **error);
Create a new process with the given flags and argument list.
The argument list is expected to be NULL-terminated.
[rename-to g_subprocess_new]
argv |
commandline arguments for the subprocess. |
[array zero-terminated=1][element-type utf8] |
flags |
flags that define the behaviour of the subprocess |
|
error |
return location for an error, or |
[nullable] |
Since: 2.40
const gchar *
g_subprocess_get_identifier (GSubprocess *subprocess);
On UNIX, returns the process ID as a decimal string.
On Windows, returns the result of GetProcessId() also as a string.
GOutputStream *
g_subprocess_get_stdin_pipe (GSubprocess *subprocess);
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
G_SUBPROCESS_FLAGS_STDIN_PIPE.
Since: 2.40
GInputStream *
g_subprocess_get_stdout_pipe (GSubprocess *subprocess);
Gets the GInputStream from which to read the stdout output of
subprocess
.
The process must have been created with
G_SUBPROCESS_FLAGS_STDOUT_PIPE.
Since: 2.40
GInputStream *
g_subprocess_get_stderr_pipe (GSubprocess *subprocess);
Gets the GInputStream from which to read the stderr output of
subprocess
.
The process must have been created with
G_SUBPROCESS_FLAGS_STDERR_PIPE.
Since: 2.40
gboolean g_subprocess_wait (GSubprocess *subprocess,GCancellable *cancellable,GError **error);
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.
Since: 2.40
void g_subprocess_wait_async (GSubprocess *subprocess,GCancellable *cancellable,GAsyncReadyCallback callback,gpointer user_data);
Wait for the subprocess to terminate.
This is the asynchronous version of g_subprocess_wait().
subprocess |
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cancellable |
a GCancellable, or |
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callback |
a GAsyncReadyCallback to call when the operation is complete |
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user_data |
user_data for |
Since: 2.40
gboolean g_subprocess_wait_finish (GSubprocess *subprocess,GAsyncResult *result,GError **error);
Collects the result of a previous call to
g_subprocess_wait_async().
Since: 2.40
gboolean g_subprocess_wait_check (GSubprocess *subprocess,GCancellable *cancellable,GError **error);
Combines g_subprocess_wait() with g_spawn_check_exit_status().
Since: 2.40
void g_subprocess_wait_check_async (GSubprocess *subprocess,GCancellable *cancellable,GAsyncReadyCallback callback,gpointer user_data);
Combines g_subprocess_wait_async() with g_spawn_check_exit_status().
This is the asynchronous version of g_subprocess_wait_check().
subprocess |
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cancellable |
a GCancellable, or |
|
callback |
a GAsyncReadyCallback to call when the operation is complete |
|
user_data |
user_data for |
Since: 2.40
gboolean g_subprocess_wait_check_finish (GSubprocess *subprocess,GAsyncResult *result,GError **error);
Collects the result of a previous call to
g_subprocess_wait_check_async().
Since: 2.40
gboolean
g_subprocess_get_successful (GSubprocess *subprocess);
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.
Since: 2.40
gboolean
g_subprocess_get_if_exited (GSubprocess *subprocess);
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.
Since: 2.40
gint
g_subprocess_get_exit_status (GSubprocess *subprocess);
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.
Since: 2.40
gboolean
g_subprocess_get_if_signaled (GSubprocess *subprocess);
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.
Since: 2.40
gint
g_subprocess_get_term_sig (GSubprocess *subprocess);
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.
Since: 2.40
gint
g_subprocess_get_status (GSubprocess *subprocess);
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_exit_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.
Since: 2.40
void g_subprocess_send_signal (GSubprocess *subprocess,gint signal_num);
Sends the UNIX signal signal_num
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.
Since: 2.40
void
g_subprocess_force_exit (GSubprocess *subprocess);
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
gboolean g_subprocess_communicate (GSubprocess *subprocess,GBytes *stdin_buf,GCancellable *cancellable,GBytes **stdout_buf,GBytes **stderr_buf,GError **error);
Communicate with the subprocess until it terminates, and all input and output has been completed.
If stdin_buf
is given, the subprocess must have been created with
G_SUBPROCESS_FLAGS_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 G_SUBPROCESS_FLAGS_STDOUT_PIPE or
G_SUBPROCESS_FLAGS_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 G_SUBPROCESS_FLAGS_STDOUT_PIPE,
stdout_buf
will contain the data read from stdout. Otherwise, for
subprocesses not created with G_SUBPROCESS_FLAGS_STDOUT_PIPE,
stdout_buf
will be set to NULL. Similar provisions apply to
stderr_buf
and G_SUBPROCESS_FLAGS_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 G_SUBPROCESS_FLAGS_STDOUT_PIPE and
G_SUBPROCESS_FLAGS_STDERR_MERGE. The merged result will be returned
in stdout_buf
and stderr_buf
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).
subprocess |
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stdin_buf |
data to send to the stdin of the subprocess, or |
[nullable] |
cancellable |
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stdout_buf |
data read from the subprocess stdout. |
[out] |
stderr_buf |
data read from the subprocess stderr. |
[out] |
error |
Since: 2.40
void g_subprocess_communicate_async (GSubprocess *subprocess,GBytes *stdin_buf,GCancellable *cancellable,GAsyncReadyCallback callback,gpointer user_data);
Asynchronous version of g_subprocess_communicate(). Complete
invocation with g_subprocess_communicate_finish().
subprocess |
Self |
|
stdin_buf |
Input data, or |
[nullable] |
cancellable |
Cancellable. |
[nullable] |
callback |
Callback |
|
user_data |
User data |
gboolean g_subprocess_communicate_finish (GSubprocess *subprocess,GAsyncResult *result,GBytes **stdout_buf,GBytes **stderr_buf,GError **error);
Complete an invocation of g_subprocess_communicate_async().
gboolean g_subprocess_communicate_utf8 (GSubprocess *subprocess,const char *stdin_buf,GCancellable *cancellable,char **stdout_buf,char **stderr_buf,GError **error);
Like g_subprocess_communicate(), but validates the output of the
process as UTF-8, and returns it as a regular NUL terminated string.
subprocess |
||
stdin_buf |
data to send to the stdin of the subprocess, or |
[nullable] |
cancellable |
||
stdout_buf |
data read from the subprocess stdout. |
[out] |
stderr_buf |
data read from the subprocess stderr. |
[out] |
error |
void g_subprocess_communicate_utf8_async (GSubprocess *subprocess,const char *stdin_buf,GCancellable *cancellable,GAsyncReadyCallback callback,gpointer user_data);
Asynchronous version of g_subprocess_communicate_utf8(). Complete
invocation with g_subprocess_communicate_utf8_finish().
subprocess |
Self |
|
stdin_buf |
Input data, or |
[nullable] |
cancellable |
Cancellable |
|
callback |
Callback |
|
user_data |
User data |
gboolean g_subprocess_communicate_utf8_finish (GSubprocess *subprocess,GAsyncResult *result,char **stdout_buf,char **stderr_buf,GError **error);
Complete an invocation of g_subprocess_communicate_utf8_async().
Flags to define the behaviour of a GSubprocess.
Note that the default for stdin is to redirect from /dev/null. For stdout and stderr the default are for them to inherit the corresponding descriptor from the calling process.
Note that it is a programmer error to mix 'incompatible' flags. For
example, you may not request both G_SUBPROCESS_FLAGS_STDOUT_PIPE and
G_SUBPROCESS_FLAGS_STDOUT_SILENCE.
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No flags. |
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create a pipe for the stdin of the
spawned process that can be accessed with
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stdin is inherited from the calling process. |
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create a pipe for the stdout of the
spawned process that can be accessed with
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silence the stdout of the spawned process (ie: redirect to /dev/null). |
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create a pipe for the stderr of the
spawned process that can be accessed with
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silence the stderr of the spawned process (ie: redirect to /dev/null). |
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merge the stderr of the spawned process with whatever the stdout happens to be. This is a good way of directing both streams to a common log file, for example. |
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spawned processes will inherit the file descriptors of their parent, unless those descriptors have been explicitly marked as close-on-exec. This flag has no effect over the "standard" file descriptors (stdin, stdout, stderr). |
Since: 2.40