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       clearerr, feof, ferror, fileno - check and reset stream status


       #include <stdio.h>

       void clearerr(FILE *stream);

       int feof(FILE *stream);

       int ferror(FILE *stream);

       int fileno(FILE *stream);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       fileno(): _POSIX_C_SOURCE


       The function clearerr() clears the end-of-file and error indicators for the stream pointed
       to by stream.

       The function feof() tests the end-of-file indicator for the stream pointed to  by  stream,
       returning  nonzero  if  it  is  set.  The end-of-file indicator can be cleared only by the
       function clearerr().

       The function ferror() tests the error indicator for  the  stream  pointed  to  by  stream,
       returning  nonzero  if it is set.  The error indicator can be reset only by the clearerr()

       The function fileno() examines the argument stream and returns the integer file descriptor
       used  to  implement this stream.  The file descriptor is still owned by stream and will be
       closed when fclose(3) is called.  Duplicate the file descriptor with dup(2) before passing
       it to code that might close it.

       For nonlocking counterparts, see unlocked_stdio(3).


       These  functions should not fail and do not set the external variable errno.  (However, in
       case fileno() detects that its argument is not a valid stream, it must return -1  and  set
       errno to EBADF.)


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

       │InterfaceAttributeValue   │
       │clearerr(), feof(), │ Thread safety │ MT-Safe │
       │ferror(), fileno()  │               │         │


       The  functions  clearerr(),  feof(),  and  ferror() conform to C89, C99, POSIX.1-2001, and

       The function fileno() conforms to POSIX.1-2001 and POSIX.1-2008.


       open(2), fdopen(3), stdio(3), unlocked_stdio(3)


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                                            2019-03-06                                  FERROR(3)