File Management

Definition of File :  File is a collection of bytes that is stored on secondary storage devices like disk.

File pointer variable : It is similar to pointer variable  , but it hold the address of the file  to perform operation on file like read,  write append   etc . 

Syntax : FILE *file_pointer

 where FILE is keyword data type  used declare file  variable.

file pointer keep the record of access.

File Opening & closing function in C   

The sequence of any kind of operation on data file is done by performing 

opening file 

performing read & write operation on file 

closing file 

fopen( ) function :

 This function is used open a file for different operation 

Syntax 

             fopen( file_name_with extension , Mode_of_operation);

  

        where file name : Address of file where located in system with extension 

                   mode : 

r  file is open for  read only. No change cannot be made  w Create a new file and write to it. If a file with the same name already exists, overwrite it – rather, erase the existing file and create a new one. a Append to the end of a file. If the file does not exist, create a new one and write to it. r+ Open an existing file. Allow both read and write operations to this file. Note – file must exist a priori. w+ Create an empty file. Allow both reading and writing. a+ Open an existing file. Allow both reading and writing.

if file name is correct ,file access is   successful, returns a pointer to a FILE object 

   else fails, returns NULL

Example 1:   fopen( "studname.txt","r") 

                    file studname is opened for read only 

 Ex 2: 

                    FILE * fp;

           fp = fopen ("studname.txt", "w");

          file  studname.txt  is opened for write only 

 How to check wether file is exit or not 

       FILE *fp = fopen(“myfile.txt”, “r”); 

     if (fp == NULL)

       { 

         //report error and try to recover 

           }

     else

     {

    //do something with the file 

      }

       fclose( ) function

      This function is used to close the file which are opened by fopen( ) function

       syntax

                  fclose(file pointer);

          Example 

          

                FILE *fp;

                fp= fopen("Stud.txt", "r");

                fclose(fp);

Next :File Operation