NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | SEE ALSO | COLOPHON

STDIO_EXT(3)              Linux Programmer's Manual             STDIO_EXT(3)

NAME         top

       __fbufsize,  __flbf,  __fpending,  __fpurge, __freadable, __freading,
       __fsetlocking, __fwritable, __fwriting,  _flushlbf  -  interfaces  to
       stdio FILE structure

SYNOPSIS         top

       #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         top

       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
              flockfile(3) in case there is more than one thread), and the
              stdio routines will not do locking until the state is reset to
              FSETLOCKING_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 stream's buffer.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌─────────────────────────────┬───────────────┬─────────────────────┐
       │Interface                    Attribute     Value               │
       ├─────────────────────────────┼───────────────┼─────────────────────┤
       │__fbufsize(), __fpending(),  │ Thread safety │ MT-Safe race:stream │
       │__fpurge(), __fsetlocking()  │               │                     │
       ├─────────────────────────────┼───────────────┼─────────────────────┤
       │__flbf(), __freadable(),     │ Thread safety │ MT-Safe             │
       │__freading(), __fwritable(), │               │                     │
       │__fwriting(), _flushlbf()    │               │                     │
       └─────────────────────────────┴───────────────┴─────────────────────┘

SEE ALSO         top

       flockfile(3), fpurge(3)

COLOPHON         top

       This page is part of release 4.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

                                 2015-03-02                     STDIO_EXT(3)