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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 associated with seekable files (e.g., disk files, but not pipes or terminals), fflush()
       discards  any  buffered data that has been fetched from the underlying file, but has not been consumed 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

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├──────────┼───────────────┼─────────┤
       │fflush()  │ Thread safety │ MT-Safe │
       └──────────┴───────────────┴─────────┘

CONFORMING TO

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

       POSIX.1-2001 did not specify the behavior for flushing of input streams, but the behavior is specified in
       POSIX.1-2008.

NOTES

       Note that fflush() flushes only 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), fileno(3), fopen(3), setbuf(3), unlocked_stdio(3)

COLOPHON

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