ferror

 

C

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Error handling

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Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Symbol index

 

File input/output

Types and objects
FILE fpos_t      stdinstdoutstderr
Functions
File access fopenfopen_s (C11) freopenfreopen_s (C11) fwide (C95) setbuf setvbuf fclose fflush Direct input/output fread fwrite Unformatted input/output fgetc fgets fputc fputs getchar getsgets_s (until C11)(C11) putchar puts ungetc fgetwcgetwc (C95)(C95) fgetws (C95) fputwcputwc (C95)(C95) fputws (C95) getwchar (C95) putwchar (C95) ungetwc (C95) Formatted input scanffscanfsscanfscanf_sfscanf_ssscanf_s (C11)(C11)(C11) wscanffwscanfswscanfwscanf_sfwscanf_sswscanf_s (C95)(C95)(C95)(C11)(C11)(C11)     vscanfvfscanfvsscanfvscanf_svfscanf_svsscanf_s (C99)(C99)(C99)(C11)(C11)(C11) vwscanfvfwscanfvswscanfvwscanf_svfwscanf_svswscanf_s (C99)(C99)(C99)(C11)(C11)(C11)	Formatted output printffprintfsprintfsnprintfprintf_sfprintf_ssprintf_ssnprintf_s (C99)(C11)(C11)(C11)(C11) wprintffwprintfswprintfwprintf_sfwprintf_sswprintf_ssnwprintf_s (C95)(C95)(C95)(C11)(C11)(C11)(C11)     vprintfvfprintfvsprintfvsnprintfvprintf_svfprintf_svsprintf_svsnprintf_s (C99)(C11)(C11)(C11)(C11) vwprintfvfwprintfvswprintfvwprintf_svfwprintf_svswprintf_svsnwprintf_s (C95)(C95)(C95)(C11)(C11)(C11)(C11) File positioning ftell fgetpos fseek fsetpos rewind Error handling clearerr feof ferror perror Operations on files remove rename tmpfiletmpfile_s (C11) tmpnamtmpnam_s (C11)

 

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