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NAME

g.parser - Provides full parser support for GRASS scripts.

SYNOPSIS

g.parser help
g.parser [-s] [-t] filename [argument,...]

Flags:

-t
Print strings for translation
-s
Write option values to standard output instead of reinvoking script

DESCRIPTION

The g.parser module provides full parser support for GRASS scripts, including an auto-generated GUI interface, help page template, and command line option checking. In this way a simple script can very quickly be made into a full-fledged GRASS module.

OPTIONS

Unless the -s switch is used, the arguments are stored in environment variables for use in your scripts. These variables are named "GIS_FLAG_<NAME>" for flags and "GIS_OPT_<NAME>" for options. The names of variables are converted to upper case. For example if an option with key input was defined in the script header, the value will be available in variable GIS_OPT_INPUT and the value of flag with key f will be available in variable GIS_FLAG_F.

For flags, the value will be "1" if the flag was given, and "0" otherwise.

If the -s switch is used, the options and flags are written to standard output in the form opt_<name>=<value> and flag_<name>=<value>, preceded by the string @ARGS_PARSED@. If this string doesn't appear as the first line of standard output, it indicates that the script was invoked with a switch such as --html-description. In this case, the data written by g.parser to standard output should be copied to the script's standard output verbatim.

Typical header definitions are as follows: 

#%module
#% description: g.parser test script   
#%end
#%flag
#% key: f
#% description: A flag
#%end
#%option
#% key: raster
#% type: string
#% gisprompt: old,cell,raster
#% description: Raster input map
#% required : yes
#%end

NOTES

An option can be instructed to allow multiple inputs by adding the following line: 
#% multiple : yes
While this will only directly change the Usage section of the help screen, the option's environmental string may be easily parsed from within a script. For example, individual comma separated identities for an option named "input" can be parsed with the following Bash shell code: 
IFS=,
for opt in $GIS_OPT_INPUT ; do
    ... "$opt"
done

A "guisection" field may be added to each option and flag to specify that the options should appear in multiple tabs in the auto-generated GUI. Any options without a guisection field go into the "Options" tab. For example: 

#% guisection: tabname
would put that option in a tab named tabname.

A "key_desc" field may be added to each option to specify the text that appears in the module's usage help section. For example: 

#% key_desc: filename
added to an input option would create the usage summary [input=filename].

If a script is run with --o, G_parser() will set GRASS_OVERWRITE=1, which has the same effect as passing --o to every module which is run from the script. Similarly, passing --q or --v will set GRASS_VERBOSE to 0 or 3 respectively, which has the same effect as passing --q or --v to every module which is run from the script. Rather than checking whether --o, --q or --v were used, you should be checking GRASS_OVERWRITE and/or GRASS_VERBOSE instead. If those variables are set, the script should behave the same way regardless of whether they were set by --o, --q or --v being passed to the script or set by other means.

AUTOMATED SCRIPT CREATION

The flag --script added to a GRASS command, generates shell output. To write out a g.parser boilerplate for easy prototyping of shell scripts, the flag --script can be added to any GRASS command. Example: 
v.in.db --script

Help page template (HTML)

The flag --html-description added to a GRASS command generates a related help page template in HTML. Example: 
v.in.db --html-description

GUI window parser (XML)

The flag --interface-description added to a GRASS command generates a related help page template in XML. Example: 
v.in.db --interface-description

GUI window parser (Tcl/Tk)

The flag --tcltk added to a GRASS command generates Tcl/Tk code suitable for building the GUI interface. Example: 
v.in.db --tcltk

TRANSLATION

g.parser provides some support for translating the options of scripts. If called with the -t switch before the script filename like this 
g.parser -t somescriptfile
g.parser will print the text of the translatable options to standard output, one per line, and exit. This is for internal use within the build system to prepare GRASS scripts for translation.

EXAMPLES

All examples below autogenerate the graphical user interface when invoked without parameters of flags:

Autogenerated GUI window

Example code for SHELL

#!/bin/sh

# g.parser demo script for shell programing

#%module
#%  description: g.parser test script   
#%end
#%flag
#%  key: f
#%  description: A flag
#%end
#%option
#% key: raster
#% type: string
#% gisprompt: old,cell,raster
#% description: Raster input map
#% required : yes
#%end
#%option
#% key: vector
#% type: string
#% gisprompt: old,vector,vector
#% description: Vector input map
#% required : yes
#%end
#%option
#% key: option1
#% type: string
#% description: An option
#% required : no
#%end

if [ -z "$GISBASE" ] ; then
    echo "You must be in GRASS GIS to run this program." 1>&2
    exit 1
fi

if [ "$1" != "@ARGS_PARSED@" ] ; then
    exec g.parser "$0" "$@"
fi

#### add your code below ####
echo ""

if [ $GIS_FLAG_F -eq 1 ] ; then
    echo "Flag -f set"
else
    echo "Flag -f not set"
fi

# test if parameter present:
if [ -n "$GIS_OPT_OPTION1" ] ; then
    echo "Value of GIS_OPT_OPTION1: '$GIS_OPT_OPTION1'"
fi

echo "Value of GIS_OPT_RASTER: '$GIS_OPT_RASTER'"
echo "Value of GIS_OPT_VECTOR: '$GIS_OPT_VECTOR'"
To run properly, the script needs to be copied into $GISBASE/scripts/ with the executable flag being set. The script will provide a GUI (as above) and the following usage help text: 
test.sh --help

Description:
 g.parser test script (python)

Usage:
 test.sh [-f] raster=string vector=string [option1=string]
   [--verbose] [--quiet]

Flags:
  -f   A flag
 --v   Verbose module output
 --q   Quiet module output

Parameters:
   raster   Raster input map
   vector   Vector input map
  option1   An option

Example code for Python

#!/usr/bin/env python

# g.parser demo script for python programing

#%module
#%  description: g.parser test script (python)
#%end
#%flag
#%  key: f
#%  description: A flag
#%end
#%option
#%  key: raster
#%  type: string
#%  gisprompt: old,cell,raster
#%  description: Raster input map
#%  required : yes
#%end
#%option
#%  key: vector
#%  type: string
#%  gisprompt: old,vector,vector
#%  description: Vector input map
#%  required : yes
#%end
#%option
#%  key: option1
#%  type: string
#%  description: An option
#%  required : no
#%end

import os
import sys

import grass.script as grass

def main():
    flag_f = flags['f']
    option1 = options['option1']
    raster = options['raster']
    vector = options['vector']

    #### add your code here ####

    if flag_f:
        print "Flag -f set"
    else:
        print "Flag -f not set"

    # test if parameter present:
    if option1:
        print "Value of option1 option: '%s'" % option1

    print "Value of raster option: '%s'" % raster
    print "Value of vector option: '%s'" % vector

    #### end of your code ####

    return 0

if __name__ == "__main__":
    options, flags = grass.parser()
    main()
The test.py script will provide a GUI (as above) and the following usage help text: 
./test.py --help

Description:
 g.parser test script (python)

Usage:
 test1.py [-f] raster=string vector=string [option1=string]
   [--verbose] [--quiet]

Flags:
  -f   A flag
 --v   Verbose module output
 --q   Quiet module output

Parameters:
   raster   Raster input map
   vector   Vector input map
  option1   An option

Example code for Perl

#!/usr/bin/perl -w
use strict;

# g.parser demo script

#%module
#%  description: g.parser test script (perl) 
#%  keywords: keyword1, keyword2
#%end
#%flag
#%  key: f
#%  description: A flag
#%end
#%option
#% key: raster
#% type: string
#% gisprompt: old,cell,raster
#% description: Raster input map
#% required : yes
#%end
#%option
#% key: vector
#% type: string
#% gisprompt: old,vector,vector
#% description: Vector input map
#% required : yes
#%end
#%option
#% key: option1
#% type: string
#% description: An option
#% required : no
#%end

if ( !$ENV{'GISBASE'} ) {
    printf(STDERR  "You must be in GRASS GIS to run this program.\n");
    exit 1;
}

if( $ARGV[0] ne '@ARGS_PARSED@' ){
    my $arg = "";
    for (my $i=0; $i < @ARGV;$i++) {
        $arg .= " $ARGV[$i] ";
    }
    system("$ENV{GISBASE}/bin/g.parser $0 $arg");
    exit;
}

#### add your code here ####
print  "\n";
if ( $ENV{'GIS_FLAG_F'} eq "1" ){
   print "Flag -f set\n"
}
else {
   print "Flag -f not set\n"
}

printf ("Value of GIS_OPT_option1: '%s'\n", $ENV{'GIS_OPT_OPTION1'});
printf ("Value of GIS_OPT_raster: '%s'\n", $ENV{'GIS_OPT_RASTER'});
printf ("Value of GIS_OPT_vect: '%s'\n", $ENV{'GIS_OPT_VECTOR'});

#### end of your code ####
The test.pl script will provide a GUI and usage help text similar to the other examples above.

SEE ALSO

d.ask, d.menu, g.ask, g.filename, g.findfile, g.tempfile and SUBMITTING_PYTHON file in the GRASS source code.

Related Wiki pages: Using GRASS with other programming languages

AUTHOR

Glynn Clements

Last changed: $Date: 2014-01-25 11:04:22 -0800 (Sat, 25 Jan 2014) $

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