From:	MERC::"uunet!CRVAX.SRI.COM!RELAY-INFO-VAX" 31-MAR-1993 21:39:40.87
To:	Info-VAX@KL.SRI.COM
CC:	
Subj:	Re: Getting parameters.

John Selph <selp001@obu.arknet.edu> writes:
>	I have seen lots of talk about telling the VAX how to send 
>parameters to a program.  I have done that a lot.  You see, I am a junior 
>CS major.  We have looked at system service routines (there are only a few 
>million).  What I want to know is how to get the command line parameters 
>from a VAX program.  The language isn't that important, since I know:  
>VAXpascal, VAX assembly, VAX fortran, etc.  I would prefer a demo in either 
>assembly or pascal.  Note that even though I know C, we don't have a C 
>compiler for our VAX so that won't help me.  Thanks!
>

in some of the previous discussions on passing parameters to a program, it
was also noted a few times on how to do this. i describe it here again.
there are two ways to do it.

A: 
   1) use the lib$get_foreign routine to obtain the _entire_ command
      line (except for the image name). i.e. if the foreign command
      EXAMPLE is setup, and the command:
		$ EXAMPLE param1 param2 param3
      is executed, calling lib$get_foreign in the program will return
      the string "param1 param2 param3".

   2) create an command definition that describes your programs' command
      structure (see Command Definition Utility). i.e.: EXAMPLE.CLD:
	module	example_parameters
	define verb example
		parameter p1
		parameter p2
		parameter p3

   3) create an object module from the above CDU description:
	$ set command/object=example_cld.obj example.cld

   4) call the cli$ routines to parse and obtain values from the command
      line.
   4a) use cli$dcl_parse to parse and validate the command line. because
      lib$get_foreign gets the command line string without the image name
      (i.e. verb), you must put the verb back into the string and pass
      this to the cli$dcl_parse routine: "example param1 param2 param3".
      the table argument to cli$dcl_parse expects an longword external
      value, i.e.:
	EXTERNAL example_parameters
   4b) use the cli$present to test if the parameter or qualifier is
      present.
   4c) use the cli$get_value to get values if the CDU description allows
      for values.

   5) link the program with the CDU object module:
	link example.obj,example_cld.obj

B:
   the other way to do the above is to follow steps 1, 2 and 4, but
   instead of creating an object module as in step 3, just add the
   command definition to your process' command definitions:
	$ set command example

   then, skip the EXTERNAL definition in 4a, and remove the
   example_cld.obj in step 5. note, you will have to do this each time
   you login before you run your example program. 

i prefer A because i don't have to execute the "$ set command example"
command each time before i want to run the program. you can put this in
your login.com file, but if you're like me, i have dozens of such
programs and this just slows down my login time too much. the
disadvantage of A is that the image must be invoked _before_ the
command line parameters are validated. in B, the command line is
validated _before_ the image is invoked.
___
rod eldridge
vms systems support      | gvrod@isuvax.iastate.edu
iowa state university    | gvrod@isuvax.bitnet