ferror(3) - Linux manual page (original) (raw)

ferror(3) Library Functions Manual ferror(3)

NAME top

   clearerr, feof, ferror - check and reset stream status

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <stdio.h>**

   **void clearerr(FILE ***_stream_**);**
   **int feof(FILE ***_stream_**);**
   **int ferror(FILE ***_stream_**);**

DESCRIPTION top

   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)](../man3/unlocked%5Fstdio.3.html).

RETURN VALUE top

   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 top

   These functions should not fail and do not set _[errno](../man3/errno.3.html)_.

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **clearerr**(), **feof**(), **ferror**()         │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   C11, POSIX.1-2008.

HISTORY top

   C89, POSIX.1-2001.

NOTES top

   POSIX.1-2008 specifies that these functions shall not change the
   value of _[errno](../man3/errno.3.html)_ if _stream_ is valid.

CAVEATS top

   Normally, programs should read the return value of an input
   function, such as [fgetc(3)](../man3/fgetc.3.html), before using functions of the [feof(3)](../man3/feof.3.html)
   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)](../man3/feof.3.html) or [ferror(3)](../man3/ferror.3.html).

SEE ALSO top

   [open(2)](../man2/open.2.html), [fdopen(3)](../man3/fdopen.3.html), [fileno(3)](../man3/fileno.3.html), [stdio(3)](../man3/stdio.3.html), [unlocked_stdio(3)](../man3/unlocked%5Fstdio.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 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)