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clearerr() - I/O Function


Tutorials Cpp

Topic

How is clearerr() used in C++?
How to reset error flag, end of file(EOF)?



Explanation

clearerr() is an I/O function that is used to reset the "error flag" associated with the stream. It also resets the end of file(EOF) indicator. When a stream function fails either because of an error or if the end of the file(EOF) has been reached, one of these internal indicators may be set.

Syntax:
    void clearerr(FILE *stream);
Example:

   #include <stdio.h>
   int main ()
   {
      FILE *fil;
      fil= fopen("clearerreg1.txt","r");
      fputc ('x',fil);
      if (ferror (fil))
        {
           printf ("ERROR!! No Write Permission\n");
           clearerr (fil);
        }
      fgetc (fil);
      if (!ferror (fil))
        {
           printf ("ERROR!! Cleared\n"); 
        }
      fclose (fil);
      return 0;
   }

Result:
    ERROR!! No Write Permission
    No ERROR!! File has read permission

In the above example a stream "fil" is used to open the file "clearerreg1.txt" with "readonly" permission. The "fputc" function tries to write a character "x" which triggers an error that is cleared by the "clearerr()" .










Note
C++ is one of the most used programming languages in the world. Also known as "C with Classes". Hope you enjoy this tutorial. Do send your feedback or suggestions on this C++ tutorial. This is a copyright content.

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