Open Source Software

syncfs(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 4.09 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/.



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