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 attrib-
utes(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 fer-
ror(3).
SEE ALSO
open(2), fdopen(3), fileno(3), stdio(3), unlocked_stdio(3)
Linux man-pages 6.7 2023-10-31 ferror(3)
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