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__FBUFSIZE(3C) Standard C Library Functions __FBUFSIZE(3C)

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 __fbufsiz(FILE *stream);

int __flbf(FILE *stream);

size_t __fpending(FILE *stream);

void __fpurge(FILE *stream);

int __freadable(FILE *stream);

int __freading(FILE *stream);

int __fsetlocking(FILE *stream, int type);

int __fwritable(FILE *stream);

int __fwriting(FILE *stream);

void _flushlbf(void);

DESCRIPTION

These functions provide portable access to the members of the
stdio(3C) FILE structure.

The __fbufsize() function returns in bytes the size of the buffer
currently in use by the given stream.

The __flbf() function returns non-zero if the stream is line-
buffered.

The __fpending function returns in bytes the amount of output pending
on a stream.

The __fpurge() function discards any pending buffered I/O on the
stream.

The __freadable() function returns non-zero if it is possible to read
from a stream.

The __freading() function returns non-zero if the file is open
readonly, or if the last operation on the stream was a read operation
such as fread(3C) or fgetc(3C). Otherwise it returns 0.

The __fsetlocking() function allows the type of locking performed by
stdio on a given stream to be controlled by the programmer.

If type is FSETLOCKING_INTERNAL, stdio performs implicit locking
around every operation on the given stream. This is the default
system behavior on that stream.

If type is FSETLOCKING_BYCALLER, stdio assumes that the caller is
responsible for maintaining the integrity of the stream in the face
of access by multiple threads. If there is only one thread accessing
the stream, nothing further needs to be done. If multiple threads
are accessing the stream, then the caller can use the flockfile(),
funlockfile(), and ftrylockfile() functions described on the
flockfile(3C) manual page to provide the appropriate locking. In both
this and the case where type is FSETLOCKING_INTERNAL, __fsetlocking()
returns the previous state of the stream.

If type is FSETLOCKING_QUERY, __fsetlocking() returns the current
state of the stream without changing it.

The __fwritable() function returns non-zero if it is possible to
write on a stream.

The __fwriting() function returns non-zero if the file is open write-
only or append-only, or if the last operation on the stream was a
write operation such as fwrite(3C) or fputc(3C). Otherwise it returns
0.

The _flushlbf() function flushes all line-buffered files. It is used
when reading from a line-buffered file.

USAGE

Although the contents of the stdio FILE structure have always been
private to the stdio implementation, some applications have needed to
obtain information about a stdio stream that was not accessible
through a supported interface. These applications have resorted to
accessing fields of the FILE structure directly, rendering them
possibly non-portable to new implementations of stdio, or more
likely, preventing enhancements to stdio that would cause those
applications to break.

In the 64-bit environment, the FILE structure is opaque. The
functions described here are provided as a means of obtaining the
information that up to now has been retrieved directly from the FILE
structure. Because they are based on the needs of existing
applications (such as mh and emacs), they may be extended as other
programs are ported. Although they may still be non-portable to
other operating systems, they will be compatible from each Solaris
release to the next. Interfaces that are more portable are under
development.

ATTRIBUTES

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