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 non-zero value if the stream is line- buffered, and zero otherwise.

The __freadable() function returns a non-zero value if the stream allows reading, and zero otherwise.

The __fwritable() function returns a non-zero value if the stream allows writing, and zero otherwise.

The __freading() function returns a non-zero 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 non-zero 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 parameter 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. (Presumably so that output to a terminal is forced out, say before reading keyboard input.)

The __fpurge() function discards the contents of the streams buffer.

SEE ALSO flockfile(3), fpurge(3)

2001-12-16 STDIO_EXT(3)