pidof
Linux has this command, but not macOS, so I write it for you.
USAGE:
./zig-out/bin/pidof [OPTIONS] [--] [program]
OPTIONS:
-s, --single Single shot - this instructs the program to only return one pid.
-S, --separator STRING Use separator as a separator put between pids.(default: )
-u, --user_only Only show process belonging to current user.
-v, --version Print version.
-h, --help Print help message.