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
       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
       flockfile(3), fpurge(3)

COLOPHON
       This  page  is  part of release 4.16 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)