FERROR(3)

NAME
clearerr, clearerr_unlocked, feof, feof_unlocked, ferror, ferror_unlocked, fileno, fileno_unlocked - check and reset stream status

LIBRARY
libc

SYNOPSIS
#include <stdio.h>
void
clearerr(FILE *stream);
void
clearerr_unlocked(FILE *stream);
int
feof(FILE *stream);
int
feof_unlocked(FILE *stream);
int
ferror(FILE *stream);
int
ferror_unlocked(FILE *stream);
int
fileno(FILE *stream);
int
fileno_unlocked(FILE *stream);

DESCRIPTION
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 non-zero if it is set. The end-of-file indicator may be cleared by explicitly calling clearerr(), or as a side-effect of other operations, e.g. fseek().

The function ferror() tests the error indicator for the stream pointed to by stream, returning non-zero if it is set.

The function fileno() examines the argument stream and returns its integer descriptor.

The clearerr_unlocked(), feof_unlocked(), ferror_unlocked(), and fileno_unlocked() functions are equivalent to clearerr(), feof(), ferror(), and fileno() respectively, except that the caller is responsible for locking the stream with flockfile(3) before calling them. These functions may be used to avoid the overhead of locking the stream and to prevent races when multiple threads are operating on the same stream.

ERRORS
These functions, except fileno(), should not fail and do not set the external variable errno.

On error, fileno() returns -1 and sets errno to one of the following values:

[EBADF]
    The stream is not associated with a file.

[EBADF]
    The file descriptor underlying stream is not a valid file descriptor.

    Note that detection of this condition is not reliable, the error might be not reported.

SEE ALSO
open(2), fdopen(3), flockfile(3), stdio(3)

STANDARDS
The functions clearerr(), feof(), and ferror() conform to isoC.

HISTORY
The functions clearerr(), feof(), ferror(), and fileno() first appeared in AT&T UNIX.