.TH parser
.SH NAME
\fIGRASS parser interface\fR \- A set of GRASS routines that 
standardizes GRASS commands.
.br
.SH 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.
.LP
The parser behaves in one of three ways:
.IP
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.
.IP
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.
.IP
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. 


.LP
\fIThis page was derived from the\fR
GRASS 4.1 Programmer's Manual, Command-Line Parsing,
\fIwhich offers detailed information about the GRASS parsing routines.\fR

