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__fsetlocking(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  cur‐
       rently 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  read‐
       only,  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  behav‐
       ior 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(), funlock‐
       file(), 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 pri‐
       vate  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-por‐
       table  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.  Inter‐
       faces that are more portable are under development.

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab()  box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
       TRIBUTE VALUE _ MT-LevelT{ __fsetlocking() is Unsafe;  all  others  are
       MT-Safe T} _ Interface StabilityCommitted


SEE ALSO
       fgetc(3C),  flockfile(3C), fputc(3C), fread(3C), fwrite(3C), stdio(3C),
       attributes(7)



Oracle Solaris 11.4               5 Feb 1998                    __fbufsize(3C)
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