Why does getpid() return pid_t instead of int?

Why does getpid() return pid_t instead of int?

c pid type-equivalence

c

What is the correct printf specifier for printing pid_t

c io printf pid

c

Check if process exists given its pid

c linux pid

c

Determine programmatically if a program is running

c linux process pid

c

How to monitor an external process for events by its PID in C?

c linux process signals pid

c

Capturing exit status code of child process

c exec fork pid

c