SYNC(2) 						     Linux Programmer's Manual							   SYNC(2)

NAME

       sync, syncfs - commit filesystem caches to disk

SYNOPSIS

       #include <unistd.h>

       void sync(void);

       int syncfs(int fd);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       sync():
	   _XOPEN_SOURCE >= 500
	       || /* Since glibc 2.19: */ _DEFAULT_SOURCE
	       || /* Glibc versions <= 2.19: */ _BSD_SOURCE

       syncfs():
	   _GNU_SOURCE

DESCRIPTION

       sync() causes all pending modifications to filesystem metadata and cached file data to be written to the underlying filesystems.

       syncfs() is like sync(), but synchronizes just the filesystem containing file referred to by the open file descriptor fd.

RETURN VALUE

       syncfs() returns 0 on success; on error, it returns -1 and sets errno to indicate the error.

ERRORS

       sync() is always successful.

       syncfs() can fail for at least the following reason:

       EBADF  fd is not a valid file descriptor.

VERSIONS

       syncfs() first appeared in Linux 2.6.39; library support was added to glibc in version 2.14.

CONFORMING TO

       sync(): POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

       syncfs() is Linux-specific.

NOTES

       Since  glibc 2.2.2, the Linux prototype for sync() is as listed above, following the various standards.	In glibc 2.2.1 and earlier, it was
       "int sync(void)", and sync() always returned 0.

       According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return  before  the  actual  writing	is
       done.   However	Linux  waits for I/O completions, and thus sync() or syncfs() provide the same guarantees as fsync called on every file in
       the system or filesystem respectively.

BUGS

       Before version 1.3.20 Linux did not wait for I/O to complete before returning.

SEE ALSO

       sync(1), fdatasync(2), fsync(2)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2017-09-15								   SYNC(2)