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
       The functions clearerr(), feof(), and ferror() conform to C99, POSIX.1-2001, and POSIX.1-2008.

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 fe‐
       of(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 6.03                                         2022-12-29                                                   ferror(3)