ferror

ferror

Defined in header <stdio.h>
int ferror( FILE *stream );

Checks the given stream for errors.

Parameters

stream

-

the file stream to check

Return value

Nonzero value if the file stream has errors occurred, ​0​ otherwise.

Example

#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#include <wchar.h>
 
int main(void)
{
    char* fname = tmpnam(NULL);
    FILE* f = fopen(fname, "wb");
    fputs("\xff\xff\n", f); // not a valid UTF-8 character sequence
    fclose(f);
 
    setlocale(LC_ALL, "en_US.utf8");
    f = fopen(fname, "rb");
    wint_t ch;
    while ((ch=fgetwc(f)) != WEOF) // attempt to read as UTF-8 fails
          printf("%#x ", ch);
 
    if (feof(f))
        puts("EOF indicator set");
    if (ferror(f))
        puts("Error indicator set");
}

Output:

Error indicator set

References

C11 standard (ISO/IEC 9899:2011):

• 7.21.10.3 The ferror function (p: 339)

C99 standard (ISO/IEC 9899:1999):

• 7.19.10.3 The ferror function (p: 305)

C89/C90 standard (ISO/IEC 9899:1990):

• 4.9.10.3 The ferror function

See also

clearerr	clears errors (function)
feof	checks for the end-of-file (function)

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