1. write a C program that will create a child process using fork()

2. the child process should run 'cat' command.

3. pipe() system call should be made.

4. the input entered in cat command should be read using pipe and the input should be changed to some other string.

5. example: input is 'dog' which is changed to 'fish'.

the new string should be written back to cat command by interefering with the program.

6. no printf should be used. the program should run in linux OS.