FFLUSH(3)

NAME
4.9 `fflush'--flush buffered file output

SYNOPSIS
     #include <stdio.h>
     int fflush(FILE *FP);
     int _fflush_r(struct _reent *REENT, FILE *FP);

DESCRIPTION
The `stdio' output functions can buffer output before delivering it to the host system, in order to minimize the overhead of system calls.
   Use `fflush' to deliver any such pending output (for the file or stream identified by FP) to the host system.
   If FP is `NULL', `fflush' delivers pending output from all open files.
   Additionally, if FP is a seekable input stream visiting a file descriptor, set the position of the file descriptor to match next unread byte, useful for obeying POSIX semantics when ending a process without consuming all input from the stream.
   The alternate function `_fflush_r' is a reentrant version, where the extra argument REENT is a pointer to a reentrancy structure, and FP must not be NULL.

RETURNS
`fflush' returns `0' unless it encounters a write error; in that situation, it returns `EOF'.

PORTABILITY
ANSI C requires `fflush'. The behavior on input streams is only specified by POSIX, and not all implementations follow POSIX rules.
   No supporting OS subroutines are required.

SEE ALSO
fflush is part of the library. The full documentation for is maintained as a Texinfo manual. If info and are properly installed at your site, the command

    info

will give you access to the complete manual.