# ferror

From cppreference.com
< c‎ | io

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

Run this code

    #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)
C++ documentation for ferror

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