Tribblix: manual page: fflush.3c

FFLUSH(3C) Standard C Library Functions FFLUSH(3C)

NAME

fflush - flush a stream

SYNOPSIS

#include <stdio.h>

int fflush(FILE *stream);

DESCRIPTION

If stream points to an output stream or an update stream in which the
most recent operation was not input, fflush() causes any unwritten
data for that stream to be written to the file, and the st_ctime and
st_mtime fields of the underlying file are marked for update.

If stream points to an input stream or an update stream into which
the most recent operation was input, that stream is flushed if it is
seekable and is not already at end-of-file. Flushing an input stream
discards any buffered input and adjusts the file pointer such that
the next input operation accesses the byte after the last one read.
A stream is seekable if the underlying file is not a pipe, FIFO,
socket, or TTY device.

If stream is a null pointer, fflush() performs this flushing action
on all streams for which the behavior is defined above.

An input stream, seekable or non-seekable, can be flushed by
explicitly calling fflush() with a non-null argument specifying that
stream.

RETURN VALUES

Upon successful completion, fflush() returns 0. Otherwise, it returns
EOF and sets errno to indicate the error.

ERRORS

The fflush() function will fail if:

EAGAIN
The O_NONBLOCK flag is set for the file descriptor
underlying stream and the process would be delayed in the
write operation.

EBADF
The file descriptor underlying stream is not valid.

EFBIG
An attempt was made to write a file that exceeds the
maximum file size or the process's file size limit; or the
file is a regular file and an attempt was made to write at
or beyond the offset maximum associated with the
corresponding stream.

EINTR
The fflush() function was interrupted by a signal.

EIO
The process is a member of a background process group
attempting to write to its controlling terminal, TOSTOP is
set, the process is neither ignoring nor blocking SIGTTOU,
and the process group of the process is orphaned. stream
was created by open_wmemstream(3C) and a wide-character or
byte sequence buffered is invalid in the current locale.

ENOSPC
There was no free space remaining on the device containing
the file.

EPIPE
An attempt is made to write to a pipe or FIFO that is not
open for reading by any process. A SIGPIPE signal will also
be sent to the calling process.

The fflush() function may fail if:

ENXIO
A request was made of a non-existent device, or the request
was beyond the limits of the device.