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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
              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.

SEE ALSO

       flockfile(3), fpurge(3)

COLOPHON

       This  page  is  part of release 3.24 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/.

                                  2001-12-16