Error Handling

Error Handling

It is possible that error may occur during  I/O operations on a file. Some situations which generates error such as:

1.                 When Trying to read beyond the end –of – file mark.

2.                 When  device overflow.

3.                 When trying to use file that has not been  opened.

4.                 When trying to perform an operations on a file , when the file is open for another type of operations.

5.                 When opening a file with an invalid name.

6.                 When attempting  to write to a write – protected file.

If such errors may not be checked  , program may return abnormal output and errors occurred. An unchecked error may result in premature termination of program or incorrect output. Error handling function in file handling provide prevention of such errors.feof() and ferror() functions help to detect errors in file.

  

feof()

This function is used for testing end of file condition.

Syntax:

                   feof(File-ptr);

As shown in above syntax File-ptr is the pointer to the file structure.

It returns true (1) integer value if all the data read from the specified file, otherwise it returns false (0).

Ex,

                 if(feof(fp))

                     printf(“\n End of file reached”);

Here , if file pointer reached at end of file then it return true (1)

ferror()

This function can be used to test file is opened properly or not . This function reports the status of the file.

Syntax:

                   ferror(File-ptr);

As shown in above syntax File-ptr is the pointer to the file structure.

It returns true (1) integer value if an error has been detected during process, otherwise it returns false (0).

Ex,

                 if(ferror(fp) !=0)

                     printf(“\n Error has occured”);

Here , if reading is not possible then it prints the error message.

NULL Pointer

When open any file fopen() function is used. This function returned file pointer. If the file can not be opened for some reason , then the function returns a NULL pointer.

This facility can be used to test whether a file has been properly opened or not.

Ex,

          if((fopen(“data.txt”,”r”))==NULL)

             printf(“\n File could not open”);

Posted By : Ruchita Pandya