describe: fix --no-exact-match
[git.git] / run-command.h
blob072db56a4dff15996889bded735dd02f2bc52e73
1 #ifndef RUN_COMMAND_H
2 #define RUN_COMMAND_H
4 #include "thread-utils.h"
6 #include "strvec.h"
8 /**
9 * The run-command API offers a versatile tool to run sub-processes with
10 * redirected input and output as well as with a modified environment
11 * and an alternate current directory.
13 * A similar API offers the capability to run a function asynchronously,
14 * which is primarily used to capture the output that the function
15 * produces in the caller in order to process it.
19 /**
20 * This describes the arguments, redirections, and environment of a
21 * command to run in a sub-process.
23 * The caller:
25 * 1. allocates and clears (using child_process_init() or
26 * CHILD_PROCESS_INIT) a struct child_process variable;
27 * 2. initializes the members;
28 * 3. calls start_command();
29 * 4. processes the data;
30 * 5. closes file descriptors (if necessary; see below);
31 * 6. calls finish_command().
33 * Special forms of redirection are available by setting these members
34 * to 1:
36 * .no_stdin, .no_stdout, .no_stderr: The respective channel is
37 * redirected to /dev/null.
39 * .stdout_to_stderr: stdout of the child is redirected to its
40 * stderr. This happens after stderr is itself redirected.
41 * So stdout will follow stderr to wherever it is
42 * redirected.
44 struct child_process {
46 /**
47 * The .args is a `struct strvec', use that API to manipulate
48 * it, e.g. strvec_pushv() to add an existing "const char **"
49 * vector.
51 * If the command to run is a git command, set the first
52 * element in the strvec to the command name without the
53 * 'git-' prefix and set .git_cmd = 1.
55 * The memory in .args will be cleaned up automatically during
56 * `finish_command` (or during `start_command` when it is unsuccessful).
58 struct strvec args;
60 /**
61 * Like .args the .env is a `struct strvec'.
63 * To modify the environment of the sub-process, specify an array of
64 * environment settings. Each string in the array manipulates the
65 * environment.
67 * - If the string is of the form "VAR=value", i.e. it contains '='
68 * the variable is added to the child process's environment.
70 * - If the string does not contain '=', it names an environment
71 * variable that will be removed from the child process's environment.
73 * The memory in .env will be cleaned up automatically during
74 * `finish_command` (or during `start_command` when it is unsuccessful).
76 struct strvec env;
77 pid_t pid;
79 int trace2_child_id;
80 uint64_t trace2_child_us_start;
81 const char *trace2_child_class;
82 const char *trace2_hook_name;
85 * Using .in, .out, .err:
86 * - Specify 0 for no redirections. No new file descriptor is allocated.
87 * (child inherits stdin, stdout, stderr from parent).
88 * - Specify -1 to have a pipe allocated as follows:
89 * .in: returns the writable pipe end; parent writes to it,
90 * the readable pipe end becomes child's stdin
91 * .out, .err: returns the readable pipe end; parent reads from
92 * it, the writable pipe end becomes child's stdout/stderr
93 * The caller of start_command() must close the returned FDs
94 * after it has completed reading from/writing to it!
95 * - Specify > 0 to set a channel to a particular FD as follows:
96 * .in: a readable FD, becomes child's stdin
97 * .out: a writable FD, becomes child's stdout/stderr
98 * .err: a writable FD, becomes child's stderr
99 * The specified FD is closed by start_command(), even in case
100 * of errors!
102 int in;
103 int out;
104 int err;
107 * To specify a new initial working directory for the sub-process,
108 * specify it in the .dir member.
110 const char *dir;
112 unsigned no_stdin:1;
113 unsigned no_stdout:1;
114 unsigned no_stderr:1;
115 unsigned git_cmd:1; /* if this is to be git sub-command */
118 * If the program cannot be found, the functions return -1 and set
119 * errno to ENOENT. Normally, an error message is printed, but if
120 * .silent_exec_failure is set to 1, no message is printed for this
121 * special error condition.
123 unsigned silent_exec_failure:1;
126 * Run the command from argv[0] using a shell (but note that we may
127 * still optimize out the shell call if the command contains no
128 * metacharacters). Note that further arguments to the command in
129 * argv[1], etc, do not need to be shell-quoted.
131 unsigned use_shell:1;
134 * Release any open file handles to the object store before running
135 * the command; This is necessary e.g. when the spawned process may
136 * want to repack because that would delete `.pack` files (and on
137 * Windows, you cannot delete files that are still in use).
139 unsigned close_object_store:1;
141 unsigned stdout_to_stderr:1;
142 unsigned clean_on_exit:1;
143 unsigned wait_after_clean:1;
144 void (*clean_on_exit_handler)(struct child_process *process);
147 #define CHILD_PROCESS_INIT { \
148 .args = STRVEC_INIT, \
149 .env = STRVEC_INIT, \
153 * The functions: start_command, finish_command, run_command do the following:
155 * - If a system call failed, errno is set and -1 is returned. A diagnostic
156 * is printed.
158 * - If the program was not found, then -1 is returned and errno is set to
159 * ENOENT; a diagnostic is printed only if .silent_exec_failure is 0.
161 * - Otherwise, the program is run. If it terminates regularly, its exit
162 * code is returned. No diagnostic is printed, even if the exit code is
163 * non-zero.
165 * - If the program terminated due to a signal, then the return value is the
166 * signal number + 128, ie. the same value that a POSIX shell's $? would
167 * report. A diagnostic is printed.
172 * Initialize a struct child_process variable.
174 void child_process_init(struct child_process *);
177 * Release the memory associated with the struct child_process.
178 * Most users of the run-command API don't need to call this
179 * function explicitly because `start_command` invokes it on
180 * failure and `finish_command` calls it automatically already.
182 void child_process_clear(struct child_process *);
184 int is_executable(const char *name);
187 * Check if the command exists on $PATH. This emulates the path search that
188 * execvp would perform, without actually executing the command so it
189 * can be used before fork() to prepare to run a command using
190 * execve() or after execvp() to diagnose why it failed.
192 * The caller should ensure that command contains no directory separators.
194 * Returns 1 if it is found in $PATH or 0 if the command could not be found.
196 int exists_in_PATH(const char *command);
199 * Start a sub-process. Takes a pointer to a `struct child_process`
200 * that specifies the details and returns pipe FDs (if requested).
201 * See below for details.
203 int start_command(struct child_process *);
206 * Wait for the completion of a sub-process that was started with
207 * start_command().
209 int finish_command(struct child_process *);
211 int finish_command_in_signal(struct child_process *);
214 * A convenience function that encapsulates a sequence of
215 * start_command() followed by finish_command(). Takes a pointer
216 * to a `struct child_process` that specifies the details.
218 int run_command(struct child_process *);
221 * Trigger an auto-gc
223 int run_auto_maintenance(int quiet);
226 * Execute the given command, sending "in" to its stdin, and capturing its
227 * stdout and stderr in the "out" and "err" strbufs. Any of the three may
228 * be NULL to skip processing.
230 * Returns -1 if starting the command fails or reading fails, and otherwise
231 * returns the exit code of the command. Any output collected in the
232 * buffers is kept even if the command returns a non-zero exit. The hint fields
233 * gives starting sizes for the strbuf allocations.
235 * The fields of "cmd" should be set up as they would for a normal run_command
236 * invocation. But note that there is no need to set the in, out, or err
237 * fields; pipe_command handles that automatically.
239 int pipe_command(struct child_process *cmd,
240 const char *in, size_t in_len,
241 struct strbuf *out, size_t out_hint,
242 struct strbuf *err, size_t err_hint);
245 * Convenience wrapper around pipe_command for the common case
246 * of capturing only stdout.
248 static inline int capture_command(struct child_process *cmd,
249 struct strbuf *out,
250 size_t hint)
252 return pipe_command(cmd, NULL, 0, out, hint, NULL, 0);
256 * The purpose of the following functions is to feed a pipe by running
257 * a function asynchronously and providing output that the caller reads.
259 * It is expected that no synchronization and mutual exclusion between
260 * the caller and the feed function is necessary so that the function
261 * can run in a thread without interfering with the caller.
263 * The caller:
265 * 1. allocates and clears (memset(&asy, 0, sizeof(asy));) a
266 * struct async variable;
267 * 2. initializes .proc and .data;
268 * 3. calls start_async();
269 * 4. processes communicates with proc through .in and .out;
270 * 5. closes .in and .out;
271 * 6. calls finish_async().
273 * There are serious restrictions on what the asynchronous function can do
274 * because this facility is implemented by a thread in the same address
275 * space on most platforms (when pthreads is available), but by a pipe to
276 * a forked process otherwise:
278 * - It cannot change the program's state (global variables, environment,
279 * etc.) in a way that the caller notices; in other words, .in and .out
280 * are the only communication channels to the caller.
282 * - It must not change the program's state that the caller of the
283 * facility also uses.
286 struct async {
289 * The function pointer in .proc has the following signature:
291 * int proc(int in, int out, void *data);
293 * - in, out specifies a set of file descriptors to which the function
294 * must read/write the data that it needs/produces. The function
295 * *must* close these descriptors before it returns. A descriptor
296 * may be -1 if the caller did not configure a descriptor for that
297 * direction.
299 * - data is the value that the caller has specified in the .data member
300 * of struct async.
302 * - The return value of the function is 0 on success and non-zero
303 * on failure. If the function indicates failure, finish_async() will
304 * report failure as well.
307 int (*proc)(int in, int out, void *data);
309 void *data;
312 * The members .in, .out are used to provide a set of fd's for
313 * communication between the caller and the callee as follows:
315 * - Specify 0 to have no file descriptor passed. The callee will
316 * receive -1 in the corresponding argument.
318 * - Specify < 0 to have a pipe allocated; start_async() replaces
319 * with the pipe FD in the following way:
321 * .in: Returns the writable pipe end into which the caller
322 * writes; the readable end of the pipe becomes the function's
323 * in argument.
325 * .out: Returns the readable pipe end from which the caller
326 * reads; the writable end of the pipe becomes the function's
327 * out argument.
329 * The caller of start_async() must close the returned FDs after it
330 * has completed reading from/writing from them.
332 * - Specify a file descriptor > 0 to be used by the function:
334 * .in: The FD must be readable; it becomes the function's in.
335 * .out: The FD must be writable; it becomes the function's out.
337 * The specified FD is closed by start_async(), even if it fails to
338 * run the function.
340 int in; /* caller writes here and closes it */
341 int out; /* caller reads from here and closes it */
342 #ifdef NO_PTHREADS
343 pid_t pid;
344 #else
345 pthread_t tid;
346 int proc_in;
347 int proc_out;
348 #endif
349 int isolate_sigpipe;
353 * Run a function asynchronously. Takes a pointer to a `struct
354 * async` that specifies the details and returns a set of pipe FDs
355 * for communication with the function. See below for details.
357 int start_async(struct async *async);
360 * Wait for the completion of an asynchronous function that was
361 * started with start_async().
363 int finish_async(struct async *async);
365 int in_async(void);
366 int async_with_fork(void);
367 void check_pipe(int err);
370 * This callback should initialize the child process and preload the
371 * error channel if desired. The preloading of is useful if you want to
372 * have a message printed directly before the output of the child process.
373 * pp_cb is the callback cookie as passed to run_processes_parallel.
374 * You can store a child process specific callback cookie in pp_task_cb.
376 * See run_processes_parallel() below for a discussion of the "struct
377 * strbuf *out" parameter.
379 * Even after returning 0 to indicate that there are no more processes,
380 * this function will be called again until there are no more running
381 * child processes.
383 * Return 1 if the next child is ready to run.
384 * Return 0 if there are currently no more tasks to be processed.
385 * To send a signal to other child processes for abortion,
386 * return the negative signal number.
388 typedef int (*get_next_task_fn)(struct child_process *cp,
389 struct strbuf *out,
390 void *pp_cb,
391 void **pp_task_cb);
394 * This callback is called whenever there are problems starting
395 * a new process.
397 * See run_processes_parallel() below for a discussion of the "struct
398 * strbuf *out" parameter.
400 * pp_cb is the callback cookie as passed into run_processes_parallel,
401 * pp_task_cb is the callback cookie as passed into get_next_task_fn.
403 * Return 0 to continue the parallel processing. To abort return non zero.
404 * To send a signal to other child processes for abortion, return
405 * the negative signal number.
407 typedef int (*start_failure_fn)(struct strbuf *out,
408 void *pp_cb,
409 void *pp_task_cb);
412 * This callback is called on every child process that finished processing.
414 * See run_processes_parallel() below for a discussion of the "struct
415 * strbuf *out" parameter.
417 * pp_cb is the callback cookie as passed into run_processes_parallel,
418 * pp_task_cb is the callback cookie as passed into get_next_task_fn.
420 * Return 0 to continue the parallel processing. To abort return non zero.
421 * To send a signal to other child processes for abortion, return
422 * the negative signal number.
424 typedef int (*task_finished_fn)(int result,
425 struct strbuf *out,
426 void *pp_cb,
427 void *pp_task_cb);
430 * Option used by run_processes_parallel(), { 0 }-initialized means no
431 * options.
433 struct run_process_parallel_opts
436 * tr2_category & tr2_label: sets the trace2 category and label for
437 * logging. These must either be unset, or both of them must be set.
439 const char *tr2_category;
440 const char *tr2_label;
443 * processes: see 'processes' in run_processes_parallel() below.
445 size_t processes;
448 * ungroup: see 'ungroup' in run_processes_parallel() below.
450 unsigned int ungroup:1;
453 * get_next_task: See get_next_task_fn() above. This must be
454 * specified.
456 get_next_task_fn get_next_task;
459 * start_failure: See start_failure_fn() above. This can be
460 * NULL to omit any special handling.
462 start_failure_fn start_failure;
465 * task_finished: See task_finished_fn() above. This can be
466 * NULL to omit any special handling.
468 task_finished_fn task_finished;
471 * data: user data, will be passed as "pp_cb" to the callback
472 * parameters.
474 void *data;
478 * Options are passed via the "struct run_process_parallel_opts" above.
480 * Runs N 'processes' at the same time. Whenever a process can be
481 * started, the callback opts.get_next_task is called to obtain the data
482 * required to start another child process.
484 * The children started via this function run in parallel. Their output
485 * (both stdout and stderr) is routed to stderr in a manner that output
486 * from different tasks does not interleave (but see "ungroup" below).
488 * If the "ungroup" option isn't specified, the API will set the
489 * "stdout_to_stderr" parameter in "struct child_process" and provide
490 * the callbacks with a "struct strbuf *out" parameter to write output
491 * to. In this case the callbacks must not write to stdout or
492 * stderr as such output will mess up the output of the other parallel
493 * processes. If "ungroup" option is specified callbacks will get a
494 * NULL "struct strbuf *out" parameter, and are responsible for
495 * emitting their own output, including dealing with any race
496 * conditions due to writing in parallel to stdout and stderr.
498 void run_processes_parallel(const struct run_process_parallel_opts *opts);
501 * Convenience function which prepares env for a command to be run in a
502 * new repo. This adds all GIT_* environment variables to env with the
503 * exception of GIT_CONFIG_PARAMETERS and GIT_CONFIG_COUNT (which cause the
504 * corresponding environment variables to be unset in the subprocess) and adds
505 * an environment variable pointing to new_git_dir. See local_repo_env in
506 * cache.h for more information.
508 void prepare_other_repo_env(struct strvec *env, const char *new_git_dir);
511 * Possible return values for start_bg_command().
513 enum start_bg_result {
514 /* child process is "ready" */
515 SBGR_READY = 0,
517 /* child process could not be started */
518 SBGR_ERROR,
520 /* callback error when testing for "ready" */
521 SBGR_CB_ERROR,
523 /* timeout expired waiting for child to become "ready" */
524 SBGR_TIMEOUT,
526 /* child process exited or was signalled before becomming "ready" */
527 SBGR_DIED,
531 * Callback used by start_bg_command() to ask whether the
532 * child process is ready or needs more time to become "ready".
534 * The callback will receive the cmd and cb_data arguments given to
535 * start_bg_command().
537 * Returns 1 is child needs more time (subject to the requested timeout).
538 * Returns 0 if child is "ready".
539 * Returns -1 on any error and cause start_bg_command() to also error out.
541 typedef int(start_bg_wait_cb)(const struct child_process *cmd, void *cb_data);
544 * Start a command in the background. Wait long enough for the child
545 * to become "ready" (as defined by the provided callback). Capture
546 * immediate errors (like failure to start) and any immediate exit
547 * status (such as a shutdown/signal before the child became "ready")
548 * and return this like start_command().
550 * We run a custom wait loop using the provided callback to wait for
551 * the child to start and become "ready". This is limited by the given
552 * timeout value.
554 * If the child does successfully start and become "ready", we orphan
555 * it into the background.
557 * The caller must not call finish_command().
559 * The opaque cb_data argument will be forwarded to the callback for
560 * any instance data that it might require. This may be NULL.
562 enum start_bg_result start_bg_command(struct child_process *cmd,
563 start_bg_wait_cb *wait_cb,
564 void *cb_data,
565 unsigned int timeout_sec);
567 #endif