Generally, the first thing you need to do is select a particular process (or some set of processes) to perform further work on. Since the /proc filesystem contains process IDs, if you already know the process ID, then your work is done, and you can continue on to the next step (see “Iterating through the list of processes” below). However, if all you know is the name of the process, then you need to search through the list of process IDs, retrieve the names of each process, and match it against the process name you're searching for.
There may be criteria other than the name that you use to select your particular process. For example, you may be interested in processes that have more than six threads, or processes that have threads in a particular state, or whatever. Regardless, you will still need to iterate through the process ID list and select your process(es).