


parser <main>	      GRASS Reference Manual	    <main> parser



NAME
     GRASS parser interface - A set of GRASS routines that
     standardizes GRASS commands.

DESCRIPTION
     A set of routines in GRASS provides a mechanism for command-
     line parsing.  The routines standardize commands that expect
     command-line arguments.  When a user is familiar with the
     general form of command-line input as defined by the parser,
     it simplifies the necessity of remembering (or at least
     guessing) required command-line arguments for any GRASS
     command.

     The parser behaves in one of three ways:

	  If no command-line arguments are entered by the user,
	  the parser searches for an interactive version of the
	  command.  If it is found, control is passed over to
	  this interactive version.  If it is not found, the
	  parser prompts the user for programmer-defined options
	  and flags.  This prompting conforms to the same
	  standard for every GRASS command that uses the parser
	  routines.

	  If command-line arguments are entered but do not
	  include all the options and flags that the programmer
	  has defined as required arguments, three things happen:
	  1) the parser passes an error message to the user
	  indicating which required options and/or flags were
	  missing from the command-line, 2) then the parser
	  displays a complete usage message for that command, and
	  finally 3) the parser cancels execution of the command.

	  If all necessary options and flags are entered on the
	  command line by the user, the parser executes the
	  command with the given options and flags.



     This page was derived from the GRASS 4.1 Programmer's
     Manual, Command-Line Parsing, which offers detailed
     information about the GRASS parsing routines.













GRASS 5.0beta		Baylor University			1



