The getarg subroutine returns a command line argument of the current process. I1 is an integer argument that specifies which command line argument to return. C1 is an argument of character type and will contain, upon return from getarg, the command line argument. If I1 is equal to 0, the program name is returned.
For greater portability, use the GET_COMMAND_ARGUMENT intrinsic instead of this procedure.
Subroutine
X is the maximum number of characters c1 can hold.