ferror(3)                  Library Functions Manual                  ferror(3)

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

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <stdio.h>

       void clearerr(FILE *stream);
       int feof(FILE *stream);
       int ferror(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 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.

       For nonlocking counterparts, see unlocked_stdio(3).

RETURN VALUE
       The feof() function returns nonzero if the end-of-file indicator is set
       for stream; otherwise, it returns zero.

       The ferror() function returns nonzero if the error indicator is set for
       stream; otherwise, it returns zero.

ERRORS
       These functions should not fail and do not set errno.

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

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |clearerr (), feof (), ferror ()             | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       C11, POSIX.1-2008.

HISTORY
       C89, POSIX.1-2001.

NOTES
       POSIX.1-2008 specifies that these functions shall not change the value
       of errno if stream is valid.

CAVEATS
       Normally, programs should read the return value of an input function,
       such as fgetc(3), before using functions of the feof(3) family.  Only
       when the function returned the sentinel value EOF it makes sense to
       distinguish between the end of a file or an error with feof(3) or
       ferror(3).

SEE ALSO
       open(2), fdopen(3), fileno(3), stdio(3), unlocked_stdio(3)

Linux man-pages 6.7               2023-10-31                         ferror(3)