Programming

Put debugging code in with fprintf(stderr,....) and perror() so you can see what errors are occuring.

Are you getting EPIPE or SIGPIPE? (Install a signal handler for SIGPIPE in the child process).

Are you reading the read end and writing the write end of the pipe?

yeah that part i s correctly working..........i.e reading and writing to the pipe......

As I told you earlier I had to create a task which has to check whether there is any message in messag e queue to read.....So I created a child process and from child process I am first reading from message queue and then writing it to the pipe....
and then I am using select through parent process to check for a active file descriptor....
I am getting data correctly....but the problem is that I had to terminate my child after it does its task..........
So no further read and writes..........
and if I will not terminate my child then the code.......after read and write operation is executed twice once by parent and one by child.......
So should I had to create child every time I had to read from message queue.......???????????

Certainly not.

How are you marking the length of a message with writing to the pipe? Are you writing the length first, then the bytes, and when it comes to reading you read the length first, then that exact number of bytes?

NO.....currently I am not considering length........because first I am testing for fixed size string.........
how should I make my child not to interfear with parents data.........
because I will not terminate my child then the code.......after read and write operation is executed twice once by parent and one by child.......

how should i use my child process......???? so that it also continously read data from message queue and write to pipe....

Yes. With either fixed length messages or some other form of message length marking.

I am sorry sir........I am unable to understand what you want to say....??????
please tell me in detail.

is it safe to use child process with loops inside it???????

Sure, why not? As long as you are using fork() and not vfork().

The parent should be terminating the child with a signal.