


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 4.1                U.S. Army CERL                         1



