fflush(3)



FFLUSH(3)                  Linux Programmer's Manual                 FFLUSH(3)

NAME
       fflush - flush a stream

SYNOPSIS
       #include <stdio.h>

       int fflush(FILE *stream);

DESCRIPTION
       For  output streams, fflush() forces a write of all user-space buffered
       data for the given output or update stream via the stream's  underlying
       write function.  For input streams, fflush() discards any buffered data
       that has been fetched from the underlying file, but has not  been  con-
       sumed by the application.  The open status of the stream is unaffected.

       If  the  stream  argument  is  NULL,  fflush()  flushes all open output
       streams.

       For a nonlocking counterpart, see unlocked_stdio(3).

RETURN VALUE
       Upon successful completion 0 is returned.  Otherwise, EOF  is  returned
       and errno is set to indicate the error.

ERRORS
       EBADF  Stream is not an open stream, or is not open for writing.

       The function fflush() may also fail and set errno for any of the errors
       specified for write(2).

ATTRIBUTES
   Multithreading (see pthreads(7))
       The fflush() function is thread-safe.

CONFORMING TO
       C89, C99, POSIX.1-2001, POSIX.1-2008.

       The standards do not specify the  behavior  for  input  streams.   Most
       other implementations behave the same as Linux.

NOTES
       Note  that fflush() only flushes the user-space buffers provided by the
       C library.  To ensure that the data is physically stored  on  disk  the
       kernel  buffers  must  be  flushed  too,  for  example, with sync(2) or
       fsync(2).

SEE ALSO
       fsync(2),   sync(2),   write(2),   fclose(3),   fopen(3),    setbuf(3),
       unlocked_stdio(3)

COLOPHON
       This  page  is  part of release 3.71 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
       http://www.kernel.org/doc/man-pages/.

GNU                               2013-07-15                         FFLUSH(3)

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