HP C/iX Library Reference Manual (30026-90004)

Chapter 5 147

HP C/iX Library Function Descriptions

ferror

Tests whether the error indicator for a stream has been set.

Syntax

#include <stdio.h>

int ferror (FILE *

stream

);

Parameters

stream

A pointer to a ﬁle to be tested.

Return Values

0 Error indicator has not been set.

≠0 Error indicator has been set.

Description

The ferror function is intended to clarify ambiguous return values from standard I/O

functions.

The ferror function returns a nonzero value if the error indicator was set on the speciﬁed

stream

. It does not reset the indicator. You need to use the clearerr function to reset it.

Because I/O functions return EOF for end-of-ﬁle and error conditions, youcan use ferror()

and feof() to distinguish between them. Also, some systems support I/O functions that

take integer data instead of characters. For these functions, you need to use ferror() and

feof() to differentiate between valid data and the EOF ﬂag.