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Friday, 11 March 2022

72.Input and output of c language: rewind()

 

rewind():

It is the function which sends the file pointer to the beginning of file.

It is mostly used when file is opened in write/read mode or append/read mode.

It accepts the file pointer as argument.

 

Function definition:

         void  rewind(FILE *p)

         {

               --------------------------

               --------------------------

               --------------------------

         }

 

 

 

 

 

 

 

 

 

 

 


Specification3:

Write a program to copy the contents of "nice1" onto "nice2" (copy) and display the contents of "nice2"

 

Program:

#include<stdio.h>

void main()

{

   FILE *p,*q;

   char ch;

   clrscr();

   p=fopen("nice1","r");                               /* opened in read mode */

   q=fopen("nice2","w+");                           /*  opened in write/read mode */

   while(1)

   {

     ch=fgetc(p);                                             /* reading from "nice1" */ 

      if(ch==-1)                                

             break;

     fputc(ch,q);                                             /* writing onto "nice2" */

   }

   printf("File is copied\n");

   fclose(p);                                                   /* closing "nice1" */

   printf("The contents of target file:\n");

   rewind(q);                                                 /* sends the file pointer to BOF */

   while(1)

   {

     ch=fgetc(q);                                           /* reading the data of  "nice2" */

     if(ch==-1)

       break;

     printf("%c",ch);                                     /* printing onto monitor */

   }

   fclose(q);                                                 /* closing "nice2" */

   getch();

}

 

Execution:

File is copied

The contents of target file:

Nice informatics

Kavali

Nellore(D.T)

A.P, INDIA

pin: 524201

 

Program explained:

1. "nice1" is opened in read mode.

2. "nice2" is opened in write/read mode

3. "nice1" is copied onto "nice2" character by character until the end of file.

4. File pointer of "nice2" is set to the beginning of file using rewind() function.

5. Contents of "nice2" are displayed as output.

 

Specification4:

Append the data to the file "nice1" and display the total contents of file.

 

Note: Adding at the tail is called append.

 

Program:

#include<stdio.h>

void main()

{

   FILE *p;

   char ch;

   clrscr();

   p=fopen("nice1","a+");

   printf("Enter the text:\n");

   while(1)

   {

     ch=getchar();

     if(ch==-1)

       break;

     fputc(ch,p);

   }

   rewind(p);

   printf("Contents of file:\n");

   while(1)

   {

      ch=fgetc(p);

      if(ch==-1)

             break;

      printf("%c",ch);

   }

   fclose(p);

   getch();

}

 

Execution

Enter the text:

Do whatever you have to do..

Whether you like it or not...

^Z

Contents of file:

Nice informatics

Kavali

Nellore(D.T)

A.P, INDIA

pin: 524201

Do whatever you have to do..

Whether you like it or not...

 

Program explained:

The file is opened in append/read mode.

Additional data is added at the end of file.

Sent the file pointer to the beginning of the file

Finally, printed the total file.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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