GRASS parser interface - A set of GRASS routines that
standardizes GRASS commands.
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:
- the parser passes an error message to the user indicating which
required options and/or flags were missing from the
- then the parser displays a complete usage message for that command,
- 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.
Last changed: $Date: 2002/01/25 05:45:34 $