ferror - Man Page

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).

InterfaceAttributeValue
clearerr(), feof(), ferror()Thread safetyMT-Safe

Standards

The functions clearerr(), feof(), and ferror() conform to C89, 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 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)

Referenced By

fgetc(3), fgetln.3bsd(3), fgetwln.3bsd(3), fread(3), fseek(3), gets(3), getw(3), perlfunc(1), puts(3), scanf(3), stdio(3).

The man pages clearerr(3) and feof(3) are aliases of ferror(3).

2022-10-18 Linux man-pages 6.01