Spawning Processes

enum GSpawnError

typedef enum
{
  G_SPAWN_ERROR_FORK,   /* fork failed due to lack of memory */
  G_SPAWN_ERROR_READ,   /* read or select on pipes failed */
  G_SPAWN_ERROR_CHDIR,  /* changing to working dir failed */
  G_SPAWN_ERROR_ACCES,  /* execv() returned EACCES */
  G_SPAWN_ERROR_PERM,   /* execv() returned EPERM */
  G_SPAWN_ERROR_2BIG,   /* execv() returned E2BIG */
  G_SPAWN_ERROR_NOEXEC, /* execv() returned ENOEXEC */
  G_SPAWN_ERROR_NAMETOOLONG, /* ""  "" ENAMETOOLONG */
  G_SPAWN_ERROR_NOENT,       /* ""  "" ENOENT */
  G_SPAWN_ERROR_NOMEM,       /* ""  "" ENOMEM */
  G_SPAWN_ERROR_NOTDIR,      /* ""  "" ENOTDIR */
  G_SPAWN_ERROR_LOOP,        /* ""  "" ELOOP   */
  G_SPAWN_ERROR_TXTBUSY,     /* ""  "" ETXTBUSY */
  G_SPAWN_ERROR_IO,          /* ""  "" EIO */
  G_SPAWN_ERROR_NFILE,       /* ""  "" ENFILE */
  G_SPAWN_ERROR_MFILE,       /* ""  "" EMFLE */
  G_SPAWN_ERROR_INVAL,       /* ""  "" EINVAL */
  G_SPAWN_ERROR_ISDIR,       /* ""  "" EISDIR */
  G_SPAWN_ERROR_LIBBAD,      /* ""  "" ELIBBAD */
  G_SPAWN_ERROR_FAILED       /* other fatal failure, error->message
                              * should explain
                              */
} GSpawnError;

Error codes returned by spawning processes.

G_SPAWN_ERROR

#define G_SPAWN_ERROR g_spawn_error_quark ()

Error domain for spawning processes. Errors in this domain will be from the GSpawnError enumeration. See GError for information on error domains.

enum GSpawnFlags

typedef enum
{
  G_SPAWN_LEAVE_DESCRIPTORS_OPEN = 1 << 0,
  G_SPAWN_DO_NOT_REAP_CHILD      = 1 << 1,
  /* look for argv[0] in the path i.e. use execvp() */
  G_SPAWN_SEARCH_PATH            = 1 << 2,
  /* Dump output to /dev/null */
  G_SPAWN_STDOUT_TO_DEV_NULL     = 1 << 3,
  G_SPAWN_STDERR_TO_DEV_NULL     = 1 << 4,
  G_SPAWN_CHILD_INHERITS_STDIN   = 1 << 5,
  G_SPAWN_FILE_AND_ARGV_ZERO     = 1 << 6
} GSpawnFlags;

Flags passed to g_spawn_sync(), g_spawn_async() and g_spawn_async_with_pipes().

GSpawnChildSetupFunc ()

void        (*GSpawnChildSetupFunc)         (gpointer user_data);

Specifies the type of the setup function passed to g_spawn_async(), g_spawn_sync() and g_spawn_async_with_pipes(). It is called in the child after GLib has performed all the setup it plans to perform but before calling exec(). Obviously, actions taken in this function will only affect the child, not the parent.

g_spawn_async_with_pipes ()

gboolean    g_spawn_async_with_pipes        (const gchar *working_directory,
                                             gchar **argv,
                                             gchar **envp,
                                             GSpawnFlags flags,
                                             GSpawnChildSetupFunc child_setup,
                                             gpointer user_data,
                                             gint *child_pid,
                                             gint *standard_input,
                                             gint *standard_output,
                                             gint *standard_error,
                                             GError **error);

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. 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; the PATH shell variable will only be searched if you pass the G_SPAWN_SEARCH_PATH flag.

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 environment.

flags should be the bitwise OR of any flags you want to affect the function's behavior. The G_SPAWN_DO_NOT_REAP_CHILD means that the child will not be automatically reaped; you must call waitpid() or handle SIGCHLD yourself, or the child will become a zombie. G_SPAWN_LEAVE_DESCRIPTORS_OPEN means that the parent's 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[0] need not be an absolute path, it will be looked for in the user's PATH. G_SPAWN_STDOUT_TO_DEV_NULL means that the child's standad output will be discarded, instead of going to the same location as the parent's standard output. G_SPAWN_STDERR_TO_DEV_NULL means that the child's standard error will be discarded. 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_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 g_spawn_async_with_pipes() uses argv[0] as the file to execute, and passes all of argv to the child.

child_setup and user_data are a function and user data to be 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(). That is, 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.

If non-NULL, child_pid will be filled with the child's process ID. You can use the process ID to send signals to the child, or to waitpid() if you specified the G_SPAWN_DO_NOT_REAP_CHILD flag.

If non-NULL, the standard_input, standard_output, standard_error 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 g_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 created.

error 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[0] 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, child_pid, standard_input, standard_output, and standard_error will not be filled with valid values.

g_spawn_async ()

gboolean    g_spawn_async                   (const gchar *working_directory,
                                             gchar **argv,
                                             gchar **envp,
                                             GSpawnFlags flags,
                                             GSpawnChildSetupFunc child_setup,
                                             gpointer user_data,
                                             gint *child_pid,
                                             GError **error);

See g_spawn_async_with_pipes() for a full description; this function simply calls the g_spawn_async_with_pipes() without any pipes.

g_spawn_sync ()

gboolean    g_spawn_sync                    (const gchar *working_directory,
                                             gchar **argv,
                                             gchar **envp,
                                             GSpawnFlags flags,
                                             GSpawnChildSetupFunc child_setup,
                                             gpointer user_data,
                                             gchar **standard_output,
                                             gchar **standard_error,
                                             gint *exit_status,
                                             GError **error);

Executes a child synchronously (waits for the child to exit before returning). All output from the child is stored in standard_output and standard_error, if those parameters are non-NULL. If exit_status is non-NULL, the exit status of the child is stored there as it would be returned by waitpid(); standard UNIX macros such as WIFEXITED() and WEXITSTATUS() must be used to evaluate the exit status. If an error occurs, no data is returned in standard_output, standard_error, or exit_status.

This function calls g_spawn_async_with_pipes() internally; see that function for full details on the other parameters.

g_spawn_command_line_async ()

gboolean    g_spawn_command_line_async      (const gchar *command_line,
                                             GError **error);

A simple version of g_spawn_async() that parses a command line with g_shell_parse_argv() and passes it to g_spawn_async(). Runs a command line in the background. Unlike g_spawn_async(), the G_SPAWN_SEARCH_PATH flag is enabled, other flags are not. Note that G_SPAWN_SEARCH_PATH can have security implications, so consider using g_spawn_async() directly if appropriate. Possible errors are those from g_shell_parse_argv() and g_spawn_async().

The same concerns on Windows apply as for g_spawn_command_line_sync().

g_spawn_command_line_sync ()

gboolean    g_spawn_command_line_sync       (const gchar *command_line,
                                             gchar **standard_output,
                                             gchar **standard_error,
                                             gint *exit_status,
                                             GError **error);

A simple version of g_spawn_sync() with little-used parameters removed, taking a command line instead of an argument vector. See g_spawn_sync() for full details. command_line will be parsed by g_shell_parse_argv(). Unlike g_spawn_sync(), the G_SPAWN_SEARCH_PATH flag is enabled. Note that G_SPAWN_SEARCH_PATH can have security implications, so consider using g_spawn_sync() directly if appropriate. Possible errors are those from g_spawn_sync() and those from g_shell_parse_argv().

On Windows, please note the implications of g_shell_parse_argv() parsing command_line. Space is a separator, and backslashes are special. Thus you cannot simply pass a command_line consisting of a canonical Windows path, like "c:\\program files\\app\\app.exe", as the backslashes will be eaten, and the space will act as a separator. You need to enclose the path with single quotes, like "'c:\\program files\\app\\app.exe'".