another app pid

[NettixCode]

hello .. in kittymemory.cpp has a code FILE *fp = fopen("/proc/self/maps", "rt");
it to get self app pid right ?
if i want to find another app pid how to code it ? can you help ?

example i want to know what gmail pid .. how i must code it ?
FILE *fp = fopen("/proc/(how to get gmail pid here)/maps", "rt");