Question

I’m new to c, and this code confuses me:

pid_t getpid(void)

if what follows the type identifier pid_tis a variable (It’s a variable declaration), but instead it’s a function call getpid(), I don’t know what why this function call is used.

Answer 1

You’re right that pid_t is a type identifier, but it’s not a variable. pid_t is the return type of the function getpid().

Every function in C has a return type. Functions are declared like this:
returntype functionName(arguments)

For example, int main(int argc, const char * argv[]) returns an int and takes two arguments.