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FFLUSH(3)		    Library Functions Manual		     FFLUSH(3)

NAME
       fflush, fflush_unlocked,	fpurge -- flush	a stream

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<stdio.h>

       int
       fflush(FILE *stream);

       int
       fflush_unlocked(FILE *stream);

       int
       fpurge(FILE *stream);

DESCRIPTION
       The function fflush() forces a write of all buffered data for the given
       output  or  update  stream  via the stream's underlying write function.
       The open	status of the stream is	unaffected.

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

       The  fflush_unlocked()  function	is equivalent to fflush(), except that
       the caller is responsible for locking the stream	with flockfile(3)  be-
       fore  calling  it.   This function may be used to avoid the overhead of
       locking the stream and to prevent races when multiple threads are oper-
       ating on	the same stream.

       The function fpurge() erases any	input or output	buffered in the	 given
       stream.	 For  output  streams this discards any	unwritten output.  For
       input streams this discards any input read from the  underlying	object
       but  not	 yet  obtained via getc(3); this includes any text pushed back
       via ungetc(3).

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

ERRORS
       [EBADF]		  The stream argument is not an	open stream.

       The function fflush() may also fail and set errno for any of the	errors
       specified for the routine write(2), except that in case of stream being
       a read-only descriptor, fflush()	returns	0.

SEE ALSO
       write(2), fclose(3), fopen(3), setbuf(3)

STANDARDS
       The fflush() function conforms to ISO/IEC 9899:1990 ("ISO C90").

HISTORY
       The  fflush()  function	first  appeared	 in  Version 4 AT&T UNIX.  The
       fpurge()	function first appeared	in 4.4BSD.

FreeBSD	15.0			  May 1, 2020			     FFLUSH(3)

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