run-command.h

#ifndef RUN_COMMAND_H
#define RUN_COMMAND_H

enum {
	ERR_RUN_COMMAND_FORK = 10000,
	ERR_RUN_COMMAND_EXEC,
	ERR_RUN_COMMAND_PIPE,
	ERR_RUN_COMMAND_WAITPID,
	ERR_RUN_COMMAND_WAITPID_WRONG_PID,
	ERR_RUN_COMMAND_WAITPID_SIGNAL,
	ERR_RUN_COMMAND_WAITPID_NOEXIT,
};

struct child_process {
	const char **argv;
	pid_t pid;
	/*
	 * Using .in, .out, .err:
	 * - Specify 0 for no redirections (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 > 0 not supported
	 *   The specified FD is closed by start_command(), even in case
	 *   of errors!
	 */
	int in;
	int out;
	int err;
	const char *dir;
	const char *const *env;
	unsigned no_stdin:1;
	unsigned no_stdout:1;
	unsigned no_stderr:1;
	unsigned git_cmd:1; /* if this is to be git sub-command */
	unsigned stdout_to_stderr:1;
	void (*preexec_cb)(void);
};

int start_command(struct child_process *);
int finish_command(struct child_process *);
int run_command(struct child_process *);

#define RUN_COMMAND_NO_STDIN 1
#define RUN_GIT_CMD	     2	/*If this is to be git sub-command */
#define RUN_COMMAND_STDOUT_TO_STDERR 4
int run_command_v_opt(const char **argv, int opt);

/*
 * 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);

/*
 * 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.
 */
struct async {
	/*
	 * proc writes to fd and closes it;
	 * returns 0 on success, non-zero on failure
	 */
	int (*proc)(int fd, void *data);
	void *data;
	int out;	/* caller reads from here and closes it */
#ifndef __MINGW32__
	pid_t pid;
#else
	HANDLE tid;
	int fd_for_proc;
#endif
};

int start_async(struct async *async);
int finish_async(struct async *async);

#endif