STDIO_EXT(3) Linux Programmer's Manual STDIO_EXT(3)NAME
__fbufsize, __flbf, __fpending, __fpurge, __freadable, __freading,
__fsetlocking, __fwritable, __fwriting, _flushlbf - interfaces to stdio
FILE structure
SYNOPSIS
#include <stdio.h>
#include <stdio_ext.h>
size_t __fbufsize(FILE *stream);
size_t __fpending(FILE *stream);
int __flbf(FILE *stream);
int __freadable(FILE *stream);
int __fwritable(FILE *stream);
int __freading(FILE *stream);
int __fwriting(FILE *stream);
int __fsetlocking(FILE *stream, int type);
void _flushlbf(void);
void __fpurge(FILE *stream);
DESCRIPTION
Solaris introduced routines to allow portable access to the internals
of the FILE structure, and glibc also implemented these.
The __fbufsize() function returns the size of the buffer currently used
by the given stream.
The __fpending() function returns the number of bytes in the output
buffer. For wide-oriented streams the unit is wide characters. This
function is undefined on buffers in reading mode, or opened read-only.
The __flbf() function returns a nonzero value if the stream is line-
buffered, and zero otherwise.
The __freadable() function returns a nonzero value if the stream allows
reading, and zero otherwise.
The __fwritable() function returns a nonzero value if the stream allows
writing, and zero otherwise.
The __freading() function returns a nonzero value if the stream is
read-only, or if the last operation on the stream was a read operation,
and zero otherwise.
The __fwriting() function returns a nonzero value if the stream is
write-only (or append-only), or if the last operation on the stream was
a write operation, and zero otherwise.
The __fsetlocking() function can be used to select the desired type of
locking on the stream. It returns the current type. The type argument
can take the following three values:
FSETLOCKING_INTERNAL
Perform implicit locking around every operation on the given
stream (except for the *_unlocked ones). This is the default.
FSETLOCKING_BYCALLER
The caller will take care of the locking (possibly using flock‐
file(3) in case there is more than one thread), and the stdio
routines will not do locking until the state is reset to FSET‐
LOCKING_INTERNAL.
FSETLOCKING_QUERY
Don't change the type of locking. (Only return it.)
The _flushlbf() function flushes all line-buffered streams. (Presum‐
ably so that output to a terminal is forced out, say before reading
keyboard input.)
The __fpurge() function discards the contents of the stream's buffer.
ATTRIBUTES
Multithreading (see pthreads(7))
The __fbufsize(), __fpending(), __fpurge() and __fsetlocking() func‐
tions do not lock the stream, so they are not thread-safe.
The __flbf(), __freadable(), __freading(), __fwritable(), __fwriting()
and _flushlbf() functions are thread-safe.
SEE ALSOflockfile(3), fpurge(3)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2013-06-21 STDIO_EXT(3)
