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hey thanks a lot jim.

Hi I want to implement the nice command in the shell that I am building. I came to know that there is a corresponding nice() system call for the same. But since I will be forking different processes...

sem_open() should ideally return the address of the semaphore whereas in this case it is returning 0 ..What can be the probable reasons for the open() call not working?

Since it is returning a zero, I think sem_open() seems to be working fine. But then after that 'segmentation fault' occurs. Notice that this fault doesn't occur if I comment out the sem_getvalue()...

I realised that you had asked for the return value of sem_open().Please read my next post after that in which I have mentioned that I got the return value as zero. I also got the return value as zero...

I also put in the check

if(sem_des == (void*)-1){
perror("sem_open failure");
printf("ERROR\n");
exit(1);
}

after sem_open() and printed
printf("%d\n",(int*)sem_des);

which...

hi I even tried out using

x=sem_getvalue(sem_des,value);

and tried printing the value of x
but the execution does not reach there..It gives a segmentation fault immediately after the sem_open...

When I execute the first 4 lines of code , it works fine. But the output gives a segmentation fault on executing the sem_getvalue() function. I looke up everywhere for the syntax and other mistakes...