public bool spawn_async_with_pipes_and_fds (string? working_directory, string argv, string? envp, SpawnFlags _flags, SpawnChildSetupFunc? child_setup, int stdin_fd, int stdout_fd, int stderr_fd, int source_fds, int target_fds, out Pid child_pid, out int standard_input = null, out int standard_output = null, out int standard_error = null) throws SpawnError
Executes a child program asynchronously (your program will not block waiting for the child to exit).
The child program is specified by the only argument that must be provided,
argv should be a
null-terminated array of strings, to be passed as the argument vector for the child. The first string in
argv is of course the name of the program to execute. By default, the name of the program must be a full path. If
contains the g_spawn_search_path flag, the `PATH` environment variable is used to search for the
flags contains the g_spawn_search_path_from_envp flag, the `PATH` variable from
envp is used to search for the executable. If both the g_spawn_search_path and
g_spawn_search_path_from_envp flags are set, the `PATH` variable from
envp takes precedence over
the environment variable.
If the program name is not a full path and g_spawn_search_path flag is not used, then the program will be run
from the current directory (or
working_directory, if specified); this might be unexpected or even dangerous in some cases when the
current directory is world-writable.
On Windows, note that all the string or string vector arguments to this function and the other `g_spawn*()` functions are in UTF-8, the GLib file name encoding. Unicode characters that are not part of the system codepage passed in these arguments will be correctly available in the spawned program only if it uses wide character API to retrieve its command line. For C programs built with Microsoft's tools it is enough to make the program have a `wmain()` instead of `main()`. `wmain()` has a wide character argument vector as parameter.
At least currently, mingw doesn't support `wmain()`, so if you use mingw to develop the spawned program, it should call get_command_line to get arguments in UTF-8.
On Windows the low-level child process creation API `CreateProcess()` doesn't use argument vectors, but a command line. The C runtime library's `spawn*()` family of functions (which spawn_async_with_pipes eventually calls) paste the argument vector elements together into a command line, and the C runtime startup code does a corresponding reconstruction of an argument vector from the command line, to be passed to `main()`. Complications arise when you have argument vector elements that contain spaces or double quotes. The `spawn*()` functions don't do any quoting or escaping, but on the other hand the startup code does do unquoting and unescaping in order to enable receiving arguments with embedded spaces or double quotes. To work around this asymmetry, spawn_async_with_pipes will do quoting and escaping on argument vector elements that need it before calling the C runtime `spawn()` function.
child_pid on Windows is a handle to the child process, not its identifier. Process handles and process identifiers
are different concepts on Windows.
envp is a null-terminated array of strings, where each string has the form `KEY=VALUE`. This
will become the child's environment. If
envp is null, the child inherits its parent's
flags should be the bitwise OR of any flags you want to affect the function's behaviour. The
g_spawn_do_not_reap_child means that the child will not automatically be reaped; you must use a child watch (
) to be notified about the death of the child process, otherwise it will stay around as a zombie process until this process exits.
Eventually you must call close_pid on the
child_pid, in order to
free resources which may be associated with the child process. (On Unix, using a child watch is equivalent to calling
waitpid or handling the `SIGCHLD` signal manually. On Windows, calling
close_pid is equivalent to calling `CloseHandle()` on the process handle
Open UNIX file descriptors marked as `FD_CLOEXEC` will be automatically closed in the child process.
g_spawn_leave_descriptors_open means that other open file descriptors will be inherited by the child; otherwise all descriptors except
stdin/stdout/stderr will be closed before calling `exec()` in the child. g_spawn_search_path means that
argv need not be an absolute path, it will be looked for in the `PATH` environment variable.
g_spawn_search_path_from_envp means need not be an absolute path, it will be looked for in the `PATH` variable from
If both g_spawn_search_path and g_spawn_search_path_from_envp are used, the
envp takes precedence over the environment.
g_spawn_child_inherits_stdin means that the child will inherit the parent's standard input (by default, the
child's standard input is attached to `/dev/null`). g_spawn_stdin_from_dev_null explicitly imposes the default
behavior. Both flags cannot be enabled at the same time and, in both cases, the
stdin_pipe_out argument is ignored.
g_spawn_stdout_to_dev_null means that the child's standard output will be discarded (by default, it goes to
the same location as the parent's standard output). g_spawn_child_inherits_stdout explicitly imposes the
default behavior. Both flags cannot be enabled at the same time and, in both cases, the
stdout_pipe_out argument is ignored.
g_spawn_stderr_to_dev_null means that the child's standard error will be discarded (by default, it goes to
the same location as the parent's standard error). g_spawn_child_inherits_stderr explicitly imposes the
default behavior. Both flags cannot be enabled at the same time and, in both cases, the
stderr_pipe_out argument is ignored.
It is valid to pass the same FD in multiple parameters (e.g. you can pass a single FD for both
, and include it in
target_fds allow zero or more FDs from this process to be remapped to different FDs in the spawned
source_fds.length is greater than zero,
target_fds must both be non-
null and the same length. Each FD in
source_fds is remapped to the FD number at the same index in
target_fds. The source and target FD may be equal to simply propagate an FD to the spawned process. FD remappings are processed
after standard FDs, so any target FDs which equal
stderr_fd will overwrite them in
the spawned process.
source_fds is supported on Windows since 2.72.
g_spawn_file_and_argv_zero means that the first element of
argv is the file to execute, while
the remaining elements are the actual argument vector to pass to the file. Normally
argv as the file to
execute, and passes all of
argv to the child.
user_data are a function and user data. On POSIX platforms, the function is called in the child after
GLib has performed all the setup it plans to perform (including creating pipes, closing file descriptors, etc.) but before calling `exec()`.
child_setup is called just before calling `exec()` in the child. Obviously actions taken in this function will only affect
the child, not the parent.
On Windows, there is no separate `fork()` and `exec()` functionality. Child processes are created and run with a single API call,
`CreateProcess()`. There is no sensible thing
child_setup could be used for on Windows so it is ignored and not called.
child_pid will on Unix be filled with the child's process ID. You can use the
process ID to send signals to the child, or to use
g_child_watch_add (or `waitpid()`) if you specified the
g_spawn_do_not_reap_child flag. On Windows,
child_pid will be filled with a handle to the child
process only if you specified the g_spawn_do_not_reap_child flag. You can then access the child process using
the Win32 API, for example wait for its termination with the `WaitFor*()` functions, or examine its exit code with `GetExitCodeProcess()`. You
should close the handle with `CloseHandle()` or close_pid when you no longer
If non-null, the
locations will be filled with file descriptors for writing to the child's standard input or reading from its standard output or standard error.
The caller of spawn_async_with_pipes must close these file
descriptors when they are no longer in use. If these parameters are null, the corresponding pipe won't be
stdin_pipe_out is null, the child's standard input is attached to `/dev/null` unless
g_spawn_child_inherits_stdin is set.
stderr_pipe_out is NULL, the child's standard error goes to the same location as the parent's standard error unless
g_spawn_stderr_to_dev_null is set.
stdout_pipe_out is NULL, the child's standard output goes to the same location as the parent's standard output unless
g_spawn_stdout_to_dev_null is set.
throws can be null to ignore errors, or non-null
to report errors. If an error is set, the function returns false. Errors are reported even if they
occur in the child (for example if the executable in `
argv` is not found). Typically the `message` field of returned errors
should be displayed to users. Possible errors are those from the g_spawn_error domain.
If an error occurs,
not be filled with valid values.
child_pid is not null and an error does not occur then the returned process reference must be
closed using close_pid.
On modern UNIX platforms, GLib can use an efficient process launching codepath driven internally by `posix_spawn()`. This has the advantage of avoiding the fork-time performance costs of cloning the parent process address space, and avoiding associated memory overcommit checks that are not relevant in the context of immediately executing a distinct process. This optimized codepath will be used provided that the following conditions are met:
- g_spawn_do_not_reap_child is set
- g_spawn_leave_descriptors_open is set
- g_spawn_search_path_from_envp is not set
- The program is of a recognised binary format, or has a shebang. Otherwise, GLib will have to execute the program through the shell, which is not done using the optimized codepath.
If you are writing a GTK application, and the program you are spawning is a graphical application too, then to ensure that the spawned program
opens its windows on the right screen, you may want to use
GAppLaunchContext, or set the
`DISPLAY` environment variable.
child's current working directory, or null to inherit parent's, in the GLib file name encoding
child's argument vector, in the GLib file name encoding; it must be non-empty and null-terminated
child's environment, or null to inherit parent's, in the GLib file name encoding
function to run in the child just before `exec()`
file descriptor to use for child's stdin, or `-1`
file descriptor to use for child's stdout, or `-1`
file descriptor to use for child's stderr, or `-1`
array of FDs from the parent process to make available in the child process
array of FDs to remap
return location for child process ID, or null
flags from SpawnFlags
number of FDs in
return location for file descriptor to read child's stderr, or null
return location for file descriptor to write to child's stdin, or null
return location for file descriptor to read child's stdout, or null
user data for
true on success, false if an error was set