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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 

.TH "FFLUSH" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"

.\" fflush 

.SH NAME

fflush \- flush a stream

.SH SYNOPSIS

.LP

\fB#include <stdio.h>

.br

.sp

int fflush(FILE *\fP\fIstream\fP\fB);

.br

\fP

.SH DESCRIPTION

.LP

If \fIstream\fP points to an output stream or an update stream in

which the most recent operation was not input,

\fIfflush\fP() shall cause any unwritten data for that stream to be

written to the file,   \ and the

\fIst_ctime\fP and \fIst_mtime\fP fields of the underlying file shall

be marked for update. 

.LP

If \fIstream\fP is a null pointer, \fIfflush\fP() shall perform this

flushing action on all streams for which the behavior is

defined above.

.SH RETURN VALUE

.LP

Upon successful completion, \fIfflush\fP() shall return 0; otherwise,

it shall set the error indicator for the stream, return

EOF,  

\ and set \fIerrno\fP to indicate the error. 

.SH ERRORS

.LP

The \fIfflush\fP() function shall fail if:

.TP 7

.B EAGAIN

The O_NONBLOCK flag is set for the file descriptor underlying \fIstream\fP

and the process would be delayed in the write

operation. 

.TP 7

.B EBADF

The file descriptor underlying \fIstream\fP is not valid. 

.TP 7

.B EFBIG

An

attempt was made to write a file that exceeds the maximum file size.

.TP 7

.B EFBIG

An attempt was made to write a file that exceeds the process' file

size limit. 

.TP 7

.B EFBIG

The file is a regular file and an attempt was made to write at or

beyond the offset maximum associated with the corresponding

stream. 

.TP 7

.B EINTR

The \fIfflush\fP() function was interrupted by a signal. 

.TP 7

.B 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. This error may also be returned under

implementation-defined conditions. 

.TP 7

.B ENOSPC

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

.TP 7

.B EPIPE

An

attempt is made to write to a pipe or FIFO that is not open for reading

by any process. A SIGPIPE signal shall also be sent to the

thread. 

.sp

.LP

The \fIfflush\fP() function may fail if:

.TP 7

.B ENXIO

A

request was made of a nonexistent device, or the request was outside

the capabilities of the device. 

.sp

.LP

\fIThe following sections are informative.\fP

.SH EXAMPLES

.SS Sending Prompts to Standard Output

.LP

The following example uses \fIprintf\fP() calls to print a series

of prompts for

information the user must enter from standard input. The \fIfflush\fP()

calls force the output to standard output. The

\fIfflush\fP() function is used because standard output is usually

buffered and the prompt may not immediately be printed on the

output or terminal. The \fIgets\fP() calls read strings from standard

input and place the

results in variables, for use later in the program.

.sp

.RS

.nf

\fB#include <stdio.h>

\&...

char user[100];

char oldpasswd[100];

char newpasswd[100];

\&...

printf("User name: ");

fflush(stdout);

gets(user);

.sp

printf("Old password: ");

fflush(stdout);

gets(oldpasswd);

.sp

printf("New password: ");

fflush(stdout);

gets(newpasswd);

\&...

\fP

.fi

.RE

.SH APPLICATION USAGE

.LP

None.

.SH RATIONALE

.LP

Data buffered by the system may make determining the validity of the

position of the current file descriptor impractical. Thus,

enforcing the repositioning of the file descriptor after \fIfflush\fP()

on streams open for \fIread\fP() is not mandated by IEEE\ Std\ 1003.1-2001.

.SH FUTURE DIRECTIONS

.LP

None.

.SH SEE ALSO

.LP

\fIgetrlimit\fP() , \fIulimit\fP() , the Base Definitions volume of

IEEE\ Std\ 1003.1-2001, \fI<stdio.h>\fP

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group. In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.opengroup.org/unix/online.html .