fsync(2)                  SYSTEM CALLS                   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                    that machine is no longer active.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. Other-
     wise, 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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