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.TH FFLUSH 3C "Nov 1, 2003"
.SH NAME
fflush \- flush a stream
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>

\fBint\fR \fBfflush\fR(\fBFILE *\fR\fIstream\fR);
.fi

.SH DESCRIPTION
.sp
.LP
If \fIstream\fR points to an output stream or an update stream in which the
most recent operation was not input, \fBfflush()\fR causes any unwritten data
for that stream to be written to the file, and the \fBst_ctime\fR and
\fBst_mtime\fR fields of the underlying file are marked for update.
.sp
.LP
If \fIstream\fR 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.
.sp
.LP
If \fIstream\fR is a null pointer, \fBfflush()\fR performs this flushing action
on all streams for which the behavior is defined above.
.sp
.LP
An input stream, seekable or non-seekable, can be flushed by explicitly calling
\fBfflush()\fR with a non-null argument specifying that stream.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBfflush()\fR returns \fB0\fR. Otherwise, it
returns \fBEOF\fR and sets \fBerrno\fR to indicate the error.
.SH ERRORS
.sp
.LP
The \fBfflush()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
The \fBO_NONBLOCK\fR flag is set for the file descriptor underlying
\fIstream\fR and the process would be delayed in the write operation.
.RE

.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The file descriptor underlying \fIstream\fR is not valid.
.RE

.sp
.ne 2
.na
\fB\fBEFBIG\fR\fR
.ad
.RS 10n
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.
.RE

.sp
.ne 2
.na
\fB\fBEINTR\fR\fR
.ad
.RS 10n
The \fBfflush()\fR function was interrupted by a signal.
.RE

.sp
.ne 2
.na
\fB\fBEIO\fR\fR
.ad
.RS 10n
The process is a member of a background process group attempting to write to
its controlling terminal, \fBTOSTOP\fR is set, the process is neither ignoring
nor blocking \fBSIGTTOU\fR, and the process group of the process is orphaned.
.RE

.sp
.ne 2
.na
\fB\fBENOSPC\fR\fR
.ad
.RS 10n
There was no free space remaining on the device containing the file.
.RE

.sp
.ne 2
.na
\fB\fBEPIPE\fR\fR
.ad
.RS 10n
An attempt is made to write to a pipe or \fBFIFO\fR that is not open for
reading by any process. A \fBSIGPIPE\fR signal will also be sent to the calling
process.
.RE

.sp
.LP
The \fBfflush()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBENXIO\fR\fR
.ad
.RS 9n
A request was made of a non-existent device, or the request was beyond the
limits of the device.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBgetrlimit\fR(2), \fBulimit\fR(2), \fBattributes\fR(5), \fBstandards\fR(5)