fileno (3) - Linux Manuals
fileno: check and reset stream status
clearerr, feof, ferror, fileno - check and reset stream status
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)):
DESCRIPTIONThe 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() function.
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).
ERRORSThese 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.)
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
CONFORMING TOThe functions clearerr(), feof(), and ferror() conform to C89, C99, POSIX.1-2001, and POSIX.1-2008.
The function fileno() conforms to POSIX.1-2001 and POSIX.1-2008.
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