clearerr

 

C

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headers

Type support

Dynamic memory management

Error handling

Program utilities

Variadic function support

Date and time utilities

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Numerics

Input/output support

Localization support

Thread support (C11)

Atomic operations (C11)

Technical Specifications

 

File input/output

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)(since 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>
void clearerr( FILE *stream );

Resets the error flags and the EOF indicator for the given file stream.

Parameters

stream

-

the file to reset the error flags for

Return value

(none)

Example

clearerr resets the EOF indicator.

Run this code

#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
    FILE* tmpf = tmpfile();
    fputs("abcde\n", tmpf);
    rewind(tmpf);
 
    int ch;
    while ((ch=fgetc(tmpf)) != EOF)   /* read/print characters including newline */
          printf("%c", ch);
 
    /* Test reason for reaching EOF. */
    if (feof(tmpf))          /* if failure caused by end-of-file condition */
    {
       puts("End of file reached");
       clearerr(tmpf);  /* clear eof indicator */
       if (feof(tmpf))
          printf("EOF indicator set\n");
       else
          printf("EOF indicator cleared\n");
    }
    else if (ferror(tmpf))   /* if failure caused by some other error      */
         {
            perror("fgetc()");
            fprintf(stderr,"fgetc() failed in file %s at line # %d\n", __FILE__,__LINE__-16);
            clearerr(tmpf);  /* clear error indicator */
            if (ferror(tmpf))
               printf("error indicator set\n");
            else
               printf("error indicator cleared\n");
            exit(EXIT_FAILURE);
         }
 
    return EXIT_SUCCESS;
}

Output:

abcde
End of file reached
EOF indicator cleared

Example

clearerr resets error indicator.

Run this code

#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
    FILE* tmpf = tmpfile();
    fputs("abcde\n", tmpf);
    fclose(tmpf);            /* close temporary file to force error */
 
    int ch;
    while ((ch=fgetc(tmpf)) != EOF)   /* read/print characters including newline */
          printf("%c", ch);
 
    /* Test reason for reaching EOF. */
    if (feof(tmpf))          /* if failure caused by end-of-file condition */
    {
       puts("End of file reached");
       clearerr(tmpf);  /* clear eof indicator */
       if (feof(tmpf))
          printf("EOF indicator set\n");
       else
          printf("EOF indicator cleared\n");
    }
    else if (ferror(tmpf))   /* if failure caused by some other error      */
         {
            perror("fgetc()");
            fprintf(stderr,"fgetc() failed in file %s at line # %d\n", __FILE__,__LINE__-16);
            clearerr(tmpf);  /* clear error indicator */
            if (ferror(tmpf))
               printf("error indicator set\n");
            else
               printf("error indicator cleared\n");
            exit(EXIT_FAILURE);
         }
 
    return EXIT_SUCCESS;
}

Output:

fgetc(): Bad file descriptor
fgetc() failed in file main.cpp at line # 11
error indicator cleared

References

• C11 standard (ISO/IEC 9899:2011):

• 7.21.10.1 The clearerr function (p: 338)

• C99 standard (ISO/IEC 9899:1999):

• 7.19.10.1 The clearerr function (p: 304)

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

• 4.9.10.1 The clearerr function

See also

feof	checks for the end-of-file (function)
perror	displays a character string corresponding of the current error to stderr (function)
ferror	checks for a file error (function)
C++ documentation for clearerr