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git/run-command.h

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19 KiB

#ifndef RUN_COMMAND_H
#define RUN_COMMAND_H
#include "thread-utils.h"
#include "strvec.h"
/**
* The run-command API offers a versatile tool to run sub-processes with
* redirected input and output as well as with a modified environment
* and an alternate current directory.
*
* A similar API offers the capability to run a function asynchronously,
* which is primarily used to capture the output that the function
* produces in the caller in order to process it.
*/
/**
* This describes the arguments, redirections, and environment of a
* command to run in a sub-process.
*
* The caller:
*
* 1. allocates and clears (using child_process_init() or
* CHILD_PROCESS_INIT) a struct child_process variable;
* 2. initializes the members;
* 3. calls start_command();
* 4. processes the data;
* 5. closes file descriptors (if necessary; see below);
* 6. calls finish_command().
*
* Special forms of redirection are available by setting these members
* to 1:
*
* .no_stdin, .no_stdout, .no_stderr: The respective channel is
* redirected to /dev/null.
*
* .stdout_to_stderr: stdout of the child is redirected to its
* stderr. This happens after stderr is itself redirected.
* So stdout will follow stderr to wherever it is
* redirected.
*/
struct child_process {
/**
* The .args is a `struct strvec', use that API to manipulate
* it, e.g. strvec_pushv() to add an existing "const char **"
* vector.
*
* If the command to run is a git command, set the first
* element in the strvec to the command name without the
* 'git-' prefix and set .git_cmd = 1.
*
* The memory in .args will be cleaned up automatically during
* `finish_command` (or during `start_command` when it is unsuccessful).
*/
struct strvec args;
/**
* Like .args the .env is a `struct strvec'.
*
* To modify the environment of the sub-process, specify an array of
* environment settings. Each string in the array manipulates the
* environment.
*
* - If the string is of the form "VAR=value", i.e. it contains '='
* the variable is added to the child process's environment.
*
* - If the string does not contain '=', it names an environment
* variable that will be removed from the child process's environment.
*
* The memory in .env will be cleaned up automatically during
* `finish_command` (or during `start_command` when it is unsuccessful).
*/
struct strvec env;
pid_t pid;
int trace2_child_id;
uint64_t trace2_child_us_start;
const char *trace2_child_class;
const char *trace2_hook_name;
/*
* Using .in, .out, .err:
* - Specify 0 for no redirections. No new file descriptor is allocated.
* (child inherits stdin, stdout, stderr from parent).
* - Specify -1 to have a pipe allocated as follows:
* .in: returns the writable pipe end; parent writes to it,
* the readable pipe end becomes child's stdin
* .out, .err: returns the readable pipe end; parent reads from
* it, the writable pipe end becomes child's stdout/stderr
* The caller of start_command() must close the returned FDs
* after it has completed reading from/writing to it!
* - Specify > 0 to set a channel to a particular FD as follows:
* .in: a readable FD, becomes child's stdin
* .out: a writable FD, becomes child's stdout/stderr
* .err: a writable FD, becomes child's stderr
* The specified FD is closed by start_command(), even in case
* of errors!
*/
int in;
int out;
int err;
/**
* To specify a new initial working directory for the sub-process,
* specify it in the .dir member.
*/
const char *dir;
unsigned no_stdin:1;
unsigned no_stdout:1;
unsigned no_stderr:1;
unsigned git_cmd:1; /* if this is to be git sub-command */
/**
* If the program cannot be found, the functions return -1 and set
* errno to ENOENT. Normally, an error message is printed, but if
* .silent_exec_failure is set to 1, no message is printed for this
* special error condition.
*/
unsigned silent_exec_failure:1;
/**
* Run the command from argv[0] using a shell (but note that we may
* still optimize out the shell call if the command contains no
* metacharacters). Note that further arguments to the command in
* argv[1], etc, do not need to be shell-quoted.
*/
unsigned use_shell:1;
/**
* Release any open file handles to the object store before running
* the command; This is necessary e.g. when the spawned process may
* want to repack because that would delete `.pack` files (and on
* Windows, you cannot delete files that are still in use).
*/
unsigned close_object_store:1;
unsigned stdout_to_stderr:1;
unsigned clean_on_exit:1;
unsigned wait_after_clean:1;
void (*clean_on_exit_handler)(struct child_process *process);
};
#define CHILD_PROCESS_INIT { \
.args = STRVEC_INIT, \
.env = STRVEC_INIT, \
}
/**
* The functions: child_process_init, start_command, finish_command,
* run_command, run_command_v_opt, run_command_v_opt_cd_env, child_process_clear
* do the following:
*
* - If a system call failed, errno is set and -1 is returned. A diagnostic
* is printed.
*
* - If the program was not found, then -1 is returned and errno is set to
* ENOENT; a diagnostic is printed only if .silent_exec_failure is 0.
*
* - Otherwise, the program is run. If it terminates regularly, its exit
* code is returned. No diagnostic is printed, even if the exit code is
* non-zero.
*
* - If the program terminated due to a signal, then the return value is the
* signal number + 128, ie. the same value that a POSIX shell's $? would
* report. A diagnostic is printed.
*
*/
/**
* Initialize a struct child_process variable.
*/
void child_process_init(struct child_process *);
/**
* Release the memory associated with the struct child_process.
* Most users of the run-command API don't need to call this
* function explicitly because `start_command` invokes it on
* failure and `finish_command` calls it automatically already.
*/
void child_process_clear(struct child_process *);
int is_executable(const char *name);
/**
* Check if the command exists on $PATH. This emulates the path search that
* execvp would perform, without actually executing the command so it
* can be used before fork() to prepare to run a command using
* execve() or after execvp() to diagnose why it failed.
*
* The caller should ensure that command contains no directory separators.
*
* Returns 1 if it is found in $PATH or 0 if the command could not be found.
*/
int exists_in_PATH(const char *command);
/**
* Start a sub-process. Takes a pointer to a `struct child_process`
* that specifies the details and returns pipe FDs (if requested).
* See below for details.
*/
int start_command(struct child_process *);
/**
* Wait for the completion of a sub-process that was started with
* start_command().
*/
int finish_command(struct child_process *);
int finish_command_in_signal(struct child_process *);
/**
* A convenience function that encapsulates a sequence of
* start_command() followed by finish_command(). Takes a pointer
* to a `struct child_process` that specifies the details.
*/
int run_command(struct child_process *);
/*
* Trigger an auto-gc
*/
int run_auto_maintenance(int quiet);
#define RUN_COMMAND_NO_STDIN (1<<0)
#define RUN_GIT_CMD (1<<1)
#define RUN_COMMAND_STDOUT_TO_STDERR (1<<2)
#define RUN_SILENT_EXEC_FAILURE (1<<3)
#define RUN_USING_SHELL (1<<4)
#define RUN_CLEAN_ON_EXIT (1<<5)
#define RUN_WAIT_AFTER_CLEAN (1<<6)
#define RUN_CLOSE_OBJECT_STORE (1<<7)
/**
* Convenience functions that encapsulate a sequence of
* start_command() followed by finish_command(). The argument argv
* specifies the program and its arguments. The argument opt is zero
* or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`,
* `RUN_COMMAND_STDOUT_TO_STDERR`, or `RUN_SILENT_EXEC_FAILURE`
* that correspond to the members .no_stdin, .git_cmd,
* .stdout_to_stderr, .silent_exec_failure of `struct child_process`.
* The argument dir corresponds the member .dir. The argument env
* corresponds to the member .env.
*/
int run_command_v_opt(const char **argv, int opt);
int run_command_v_opt_tr2(const char **argv, int opt, const char *tr2_class);
/*
* env (the environment) is to be formatted like environ: "VAR=VALUE".
* To unset an environment variable use just "VAR".
*/
int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env);
int run_command_v_opt_cd_env_tr2(const char **argv, int opt, const char *dir,
const char *const *env, const char *tr2_class);
/**
* Execute the given command, sending "in" to its stdin, and capturing its
* stdout and stderr in the "out" and "err" strbufs. Any of the three may
* be NULL to skip processing.
*
* Returns -1 if starting the command fails or reading fails, and otherwise
* returns the exit code of the command. Any output collected in the
* buffers is kept even if the command returns a non-zero exit. The hint fields
* gives starting sizes for the strbuf allocations.
*
* The fields of "cmd" should be set up as they would for a normal run_command
* invocation. But note that there is no need to set the in, out, or err
* fields; pipe_command handles that automatically.
*/
int pipe_command(struct child_process *cmd,
const char *in, size_t in_len,
struct strbuf *out, size_t out_hint,
struct strbuf *err, size_t err_hint);
/**
* Convenience wrapper around pipe_command for the common case
* of capturing only stdout.
*/
static inline int capture_command(struct child_process *cmd,
struct strbuf *out,
size_t hint)
{
return pipe_command(cmd, NULL, 0, out, hint, NULL, 0);
}
/*
* The purpose of the following functions is to feed a pipe by running
* a function asynchronously and providing output that the caller reads.
*
* It is expected that no synchronization and mutual exclusion between
* the caller and the feed function is necessary so that the function
* can run in a thread without interfering with the caller.
*
* The caller:
*
* 1. allocates and clears (memset(&asy, 0, sizeof(asy));) a
* struct async variable;
* 2. initializes .proc and .data;
* 3. calls start_async();
* 4. processes communicates with proc through .in and .out;
* 5. closes .in and .out;
* 6. calls finish_async().
*
* There are serious restrictions on what the asynchronous function can do
* because this facility is implemented by a thread in the same address
* space on most platforms (when pthreads is available), but by a pipe to
* a forked process otherwise:
*
* - It cannot change the program's state (global variables, environment,
* etc.) in a way that the caller notices; in other words, .in and .out
* are the only communication channels to the caller.
*
* - It must not change the program's state that the caller of the
* facility also uses.
*
*/
struct async {
/**
* The function pointer in .proc has the following signature:
*
* int proc(int in, int out, void *data);
*
* - in, out specifies a set of file descriptors to which the function
* must read/write the data that it needs/produces. The function
* *must* close these descriptors before it returns. A descriptor
* may be -1 if the caller did not configure a descriptor for that
* direction.
*
* - data is the value that the caller has specified in the .data member
* of struct async.
*
* - The return value of the function is 0 on success and non-zero
* on failure. If the function indicates failure, finish_async() will
* report failure as well.
*
*/
int (*proc)(int in, int out, void *data);
void *data;
/**
* The members .in, .out are used to provide a set of fd's for
* communication between the caller and the callee as follows:
*
* - Specify 0 to have no file descriptor passed. The callee will
* receive -1 in the corresponding argument.
*
* - Specify < 0 to have a pipe allocated; start_async() replaces
* with the pipe FD in the following way:
*
* .in: Returns the writable pipe end into which the caller
* writes; the readable end of the pipe becomes the function's
* in argument.
*
* .out: Returns the readable pipe end from which the caller
* reads; the writable end of the pipe becomes the function's
* out argument.
*
* The caller of start_async() must close the returned FDs after it
* has completed reading from/writing from them.
*
* - Specify a file descriptor > 0 to be used by the function:
*
* .in: The FD must be readable; it becomes the function's in.
* .out: The FD must be writable; it becomes the function's out.
*
* The specified FD is closed by start_async(), even if it fails to
* run the function.
*/
int in; /* caller writes here and closes it */
int out; /* caller reads from here and closes it */
#ifdef NO_PTHREADS
pid_t pid;
#else
pthread_t tid;
int proc_in;
int proc_out;
#endif
int isolate_sigpipe;
};
/**
* Run a function asynchronously. Takes a pointer to a `struct
* async` that specifies the details and returns a set of pipe FDs
* for communication with the function. See below for details.
*/
int start_async(struct async *async);
/**
* Wait for the completion of an asynchronous function that was
* started with start_async().
*/
int finish_async(struct async *async);
int in_async(void);
int async_with_fork(void);
void check_pipe(int err);
/**
* This callback should initialize the child process and preload the
* error channel if desired. The preloading of is useful if you want to
* have a message printed directly before the output of the child process.
* pp_cb is the callback cookie as passed to run_processes_parallel.
* You can store a child process specific callback cookie in pp_task_cb.
*
* See run_processes_parallel() below for a discussion of the "struct
* strbuf *out" parameter.
*
* Even after returning 0 to indicate that there are no more processes,
* this function will be called again until there are no more running
* child processes.
*
* Return 1 if the next child is ready to run.
* Return 0 if there are currently no more tasks to be processed.
* To send a signal to other child processes for abortion,
* return the negative signal number.
*/
typedef int (*get_next_task_fn)(struct child_process *cp,
struct strbuf *out,
void *pp_cb,
void **pp_task_cb);
/**
* This callback is called whenever there are problems starting
* a new process.
*
* See run_processes_parallel() below for a discussion of the "struct
* strbuf *out" parameter.
*
* pp_cb is the callback cookie as passed into run_processes_parallel,
* pp_task_cb is the callback cookie as passed into get_next_task_fn.
*
* Return 0 to continue the parallel processing. To abort return non zero.
* To send a signal to other child processes for abortion, return
* the negative signal number.
*/
typedef int (*start_failure_fn)(struct strbuf *out,
void *pp_cb,
void *pp_task_cb);
/**
* This callback is called on every child process that finished processing.
*
* See run_processes_parallel() below for a discussion of the "struct
* strbuf *out" parameter.
*
* pp_cb is the callback cookie as passed into run_processes_parallel,
* pp_task_cb is the callback cookie as passed into get_next_task_fn.
*
* Return 0 to continue the parallel processing. To abort return non zero.
* To send a signal to other child processes for abortion, return
* the negative signal number.
*/
typedef int (*task_finished_fn)(int result,
struct strbuf *out,
void *pp_cb,
void *pp_task_cb);
/**
* Runs up to n processes at the same time. Whenever a process can be
* started, the callback get_next_task_fn is called to obtain the data
* required to start another child process.
*
* The children started via this function run in parallel. Their output
* (both stdout and stderr) is routed to stderr in a manner that output
* from different tasks does not interleave (but see "ungroup" below).
*
* start_failure_fn and task_finished_fn can be NULL to omit any
* special handling.
*
* If the "ungroup" option isn't specified, the API will set the
* "stdout_to_stderr" parameter in "struct child_process" and provide
* the callbacks with a "struct strbuf *out" parameter to write output
* to. In this case the callbacks must not write to stdout or
* stderr as such output will mess up the output of the other parallel
* processes. If "ungroup" option is specified callbacks will get a
* NULL "struct strbuf *out" parameter, and are responsible for
* emitting their own output, including dealing with any race
* conditions due to writing in parallel to stdout and stderr.
* The "ungroup" option can be enabled by setting the global
* "run_processes_parallel_ungroup" to "1" before invoking
* run_processes_parallel(), it will be set back to "0" as soon as the
* API reads that setting.
*/
extern int run_processes_parallel_ungroup;
int run_processes_parallel(int n,
get_next_task_fn,
start_failure_fn,
task_finished_fn,
void *pp_cb);
int run_processes_parallel_tr2(int n, get_next_task_fn, start_failure_fn,
task_finished_fn, void *pp_cb,
const char *tr2_category, const char *tr2_label);
/**
* Convenience function which prepares env for a command to be run in a
* new repo. This adds all GIT_* environment variables to env with the
* exception of GIT_CONFIG_PARAMETERS and GIT_CONFIG_COUNT (which cause the
* corresponding environment variables to be unset in the subprocess) and adds
* an environment variable pointing to new_git_dir. See local_repo_env in
* cache.h for more information.
*/
void prepare_other_repo_env(struct strvec *env, const char *new_git_dir);
/**
* Possible return values for start_bg_command().
*/
enum start_bg_result {
/* child process is "ready" */
SBGR_READY = 0,
/* child process could not be started */
SBGR_ERROR,
/* callback error when testing for "ready" */
SBGR_CB_ERROR,
/* timeout expired waiting for child to become "ready" */
SBGR_TIMEOUT,
/* child process exited or was signalled before becomming "ready" */
SBGR_DIED,
};
/**
* Callback used by start_bg_command() to ask whether the
* child process is ready or needs more time to become "ready".
*
* The callback will receive the cmd and cb_data arguments given to
* start_bg_command().
*
* Returns 1 is child needs more time (subject to the requested timeout).
* Returns 0 if child is "ready".
* Returns -1 on any error and cause start_bg_command() to also error out.
*/
typedef int(start_bg_wait_cb)(const struct child_process *cmd, void *cb_data);
/**
* Start a command in the background. Wait long enough for the child
* to become "ready" (as defined by the provided callback). Capture
* immediate errors (like failure to start) and any immediate exit
* status (such as a shutdown/signal before the child became "ready")
* and return this like start_command().
*
* We run a custom wait loop using the provided callback to wait for
* the child to start and become "ready". This is limited by the given
* timeout value.
*
* If the child does successfully start and become "ready", we orphan
* it into the background.
*
* The caller must not call finish_command().
*
* The opaque cb_data argument will be forwarded to the callback for
* any instance data that it might require. This may be NULL.
*/
enum start_bg_result start_bg_command(struct child_process *cmd,
start_bg_wait_cb *wait_cb,
void *cb_data,
unsigned int timeout_sec);
#endif