Question

What is the practice on comparing a pthread_t variable to int. I display a list of all thread ids and I take in input from the user specifying which thread to kill, using the id. So how do I compare the input from the user to all of the pthread_t variables.

Answer 1

What is the practice on comparing a pthread_t variable to int.

You don’t. The type pthread_t is opaque: it need not be an integer. You should instead use the pid_t as returned by gettid.