## 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:

1. 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.

2. 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.

3. 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.

Last changed: $Date: 2002/01/25 05:45:34 $