ferror(3) — Linux manual page

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)

COLOPHON

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Linux man-pages 6.9.1          2024-05-02                      ferror(3)

Pages that refer to this page: EOF(3const), ferror(3), fgetc(3), fread(3), fseek(3), gets(3), getw(3), puts(3), scanf(3), stdio(3)

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