fsync(2)                                                           fsync(2)


   NAME
         fsync - synchronize a file's in-memory state with that on the
         physical medium

   SYNOPSIS
         #include <unistd.h>

         int fsync(int fildes);

   DESCRIPTION
         fsync moves all modified data and attributes of fildes to a storage
         device.  When fsync returns, all in-memory modified copies of buffers
         associated with fildes have been written to the physical medium.
         fsync is different from sync, which schedules disk I/O for all files
         but returns before the I/O completes.

         fsync should be used by programs that require that a file be in a
         known state.  For example, a program that contains a simple
         transaction facility might use fsync to ensure that all changes to a
         file or files caused by a given transaction were recorded on a
         storage medium.

         fsync fails if one or more of the following are true:

         EBADF          fildes is not a valid file descriptor open for
                        writing.

         ENOLINK        fildes is on a remote machine and the link on that
                        machine is no longer active.

         EINTR          A signal was caught during execution of the fsync
                        system call.

         EIO            An I/O error occurred while reading from or writing to
                        the file system.

   DIAGNOSTICS
         Upon successful completion, a value of 0 is returned. Otherwise, a
         value of -1 is returned and errno is set to indicate the error.

   NOTES
         The way the data reach the physical medium depends on both
         implementation and hardware.  fsync returns when the device driver
         tells it that the write has taken place.

   SEE ALSO
         sync(2).






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