ARG

 ──ARG(─┬───────────────────┬─)───────────
          └─n──┬───────────┬──┘
               └─,option───┘

ARG returns an argument string, or information about the argument strings to a program or internal routine.

If you do not specify a parameter, the number of arguments passed to the program or internal routine is returned.

If only n is specified, the n th argument string is returned. If the argument string does not exist, the null string is returned. n must be a positive whole number.

If you specify option, ARG tests for the existence of the n th argument string. Valid options (of which only the capitalized letter is significant and all others are ignored) are:

Exists

Returns 1 if the n th argument exists; that is, if it was explicitly specified when the routine was called. Returns 0 otherwise.
Omitted
Returns 1 if the nth argument was omitted; that is, if it was not explicitly specified when the routine was called. Returns 0 otherwise.

Here are some examples:

/*  following "Call name;" (no arguments) */ARG( )        ->    0
ARG(1)        ->    ''
ARG(2)        ->    ''
ARG(1,'e')    ->    0
ARG(1,'O')    ->    1

/*  following "Call name 'a',,'b';" */
ARG( )        ->    3
ARG(1)        ->    'a'
ARG(2)        ->    ''
ARG(3)        ->    'b'
ARG(n)        ->    ''    /* for n>=4 */
ARG(1,'e')    ->    1
ARG(2,'E')    ->    0
ARG(2,'O')    ->    1
ARG(3,'o')    ->    0
ARG(4,'o')    ->    1

Notes:

• You can retrieve and directly parse the argument strings to a program or internal routine using the ARG or PARSE ARG instructions.
  
• Programs called as commands can have only 0 or 1 argument strings. The program has no argument strings if it is called with the name only and has 1 argument string if anything else (including blanks) is included with the command.
  
• Programs called by the REXXSTART entry point can have multiple argument strings.

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