fsync(2)                         UNIX System V                         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                     is no longer active.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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