fsync - phpMan

FSYNC(2)                   Linux Programmer’s Manual                  FSYNC(2)



NAME
       fsync, fdatasync - synchronize a file’s complete in-core state with that on disk

SYNOPSIS
       #include <unistd.h>

       int fsync(int fd);

       int fdatasync(int fd);

DESCRIPTION
       fsync  copies  all  in-core  parts  of  a  file to disk, and waits until the device
       reports that all parts are on stable storage.  It also updates metadata stat infor-
       mation.  It  does not necessarily ensure that the entry in the directory containing
       the file has also reached disk.  For that an explicit fsync on the file  descriptor
       of the directory is also needed.

       fdatasync does the same as fsync but only flushes user data, not the meta data like
       the mtime or atime.


RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropri-
       ately.

ERRORS
       EBADF  fd is not a valid file descriptor open for writing.

       EROFS, EINVAL
              fd is bound to a special file which does not support synchronization.

       EIO    An error occurred during synchronization.

NOTES
       In case the hard disk has write cache enabled, the data may not really be on perma-
       nent storage when fsync/fdatasync return.

       When an ext2 file system is mounted with the sync  option,  directory  entries  are
       also implicitly synced by fsync.

       On kernels before 2.4, fsync on big files can be inefficient.  An alternative might
       be to use the O_SYNC flag to open(2).

CONFORMING TO
       POSIX.1b (formerly POSIX.4)

SEE ALSO
       bdflush(2), open(2), sync(2), mount(8), update(8), sync(8)



Linux 1.3.85                      2001-04-18                          FSYNC(2)

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