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



NAME
       sync, syncfs - commit buffer cache 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():
           _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

       syncfs():
           _GNU_SOURCE

DESCRIPTION
       sync()  causes  all  buffered modifications to file metadata and 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(): SVr4, 4.3BSD, POSIX.1-2001.

       syncfs() is Linux-specific.

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

BUGS
       According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes,
       but may return before the actual writing is done.  However,  since  version  1.3.20  Linux
       does  actually  wait.   (This  still  does not guarantee data integrity: modern disks have
       large caches.)

SEE ALSO
       bdflush(2), fdatasync(2), fsync(2), sync(1)

COLOPHON
       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



Linux                                       2014-08-19                                    SYNC(2)