busybox/coreutils/sync.c

/* vi: set sw=4 ts=4: */
/*
 * Mini sync implementation for busybox
 *
 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
 * Copyright (C) 2015 by Ari Sundholm <ari@tuxera.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//config:config SYNC
//config:	bool "sync (769 bytes)"
//config:	default y
//config:	help
//config:	sync is used to flush filesystem buffers.
//config:config FEATURE_SYNC_FANCY
//config:	bool "Enable -d and -f flags (requires syncfs(2) in libc)"
//config:	default y
//config:	depends on SYNC
//config:	help
//config:	sync -d FILE... executes fdatasync() on each FILE.
//config:	sync -f FILE... executes syncfs() on each FILE.

//applet:IF_SYNC(APPLET_NOFORK(sync, sync, BB_DIR_BIN, BB_SUID_DROP, sync))

//kbuild:lib-$(CONFIG_SYNC) += sync.o

/* BB_AUDIT SUSv3 N/A -- Matches GNU behavior. */

//usage:#define sync_trivial_usage
//usage:       ""IF_FEATURE_SYNC_FANCY("[-df] [FILE]...")
//usage:#define sync_full_usage "\n\n"
//usage:    IF_NOT_FEATURE_SYNC_FANCY(
//usage:       "Write all buffered blocks to disk"
//usage:    )
//usage:    IF_FEATURE_SYNC_FANCY(
//usage:       "Write all buffered blocks (in FILEs) to disk"
//usage:     "\n	-d	Avoid syncing metadata"
//usage:     "\n	-f	Sync filesystems underlying FILEs"
//usage:    )

#include "libbb.h"

/* This is a NOFORK applet. Be very careful! */

int sync_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sync_main(int argc UNUSED_PARAM, char **argv IF_NOT_DESKTOP(UNUSED_PARAM))
{
#if !ENABLE_FEATURE_SYNC_FANCY
	/* coreutils-6.9 compat */
	bb_warn_ignoring_args(argv[1]);
	sync();
	return EXIT_SUCCESS;
#else
	unsigned opts;
	int ret = EXIT_SUCCESS;

	enum {
		OPT_DATASYNC = (1 << 0),
		OPT_SYNCFS   = (1 << 1),
	};

	opt_complementary = "d--f:f--d";
	opts = getopt32(argv, "df");
	argv += optind;

	/* Handle the no-argument case. */
	if (!argv[0])
		sync();

	while (*argv) {
		int fd = open_or_warn(*argv, O_RDONLY);

		if (fd < 0) {
			ret = EXIT_FAILURE;
			goto next;
		}
		if (opts & OPT_DATASYNC) {
			if (fdatasync(fd))
				goto err;
			goto do_close;
		}
		if (opts & OPT_SYNCFS) {
			/*
			 * syncfs is documented to only fail with EBADF,
			 * which can't happen here. So, no error checks.
			 */
			syncfs(fd);
			goto do_close;
		}
		if (fsync(fd)) {
 err:
			bb_simple_perror_msg(*argv);
			ret = EXIT_FAILURE;
		}
 do_close:
		close(fd);
 next:
		++argv;
	}

	return ret;
#endif
}