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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()    |               |                     |
     +-----------------------------+---------------+---------------------+