Function getRestoreCommand

src/bin/pg_rewind/pg_rewind.c:1124–1180

* Get value of GUC parameter restore_command from the target cluster. * * This uses a logic based on "postgres -C" to get the value from the * cluster. */

 * cluster.
 */
static void
getRestoreCommand(const char *argv0)
{
	int			rc;
	char		postgres_exec_path[MAXPGPATH],
				postgres_cmd[MAXPGPATH],
				cmd_output[MAXPGPATH];

	if (!restore_wal)
		return;

	/* find postgres executable */
	rc = find_other_exec(argv0, "postgres",
						 PG_BACKEND_VERSIONSTR,
						 postgres_exec_path);

	if (rc < 0)
	{
		char		full_path[MAXPGPATH];

		if (find_my_exec(argv0, full_path) < 0)
			strlcpy(full_path, progname, sizeof(full_path));

		if (rc == -1)
			pg_log_error("The program \"%s\" is needed by %s but was not found in the\n"
						 "same directory as \"%s\".\n"
						 "Check your installation.",
						 "postgres", progname, full_path);
		else
			pg_log_error("The program \"%s\" was found by \"%s\"\n"
						 "but was not the same version as %s.\n"
						 "Check your installation.",
						 "postgres", full_path, progname);
		exit(1);
	}

	/*
	 * Build a command able to retrieve the value of GUC parameter
	 * restore_command, if set.
	 */
	snprintf(postgres_cmd, sizeof(postgres_cmd),
			 "\"%s\" -D \"%s\" -C restore_command",
			 postgres_exec_path, datadir_target);

	if (!pipe_read_line(postgres_cmd, cmd_output, sizeof(cmd_output)))
		exit(1);

	(void) pg_strip_crlf(cmd_output);

	if (strcmp(cmd_output, "") == 0)
		pg_fatal("restore_command is not set in the target cluster");

	restore_command = pg_strdup(cmd_output);

	pg_log_debug("using for rewind restore_command = \'%s\'",
				 restore_command);
}