.TH g.parser 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBg.parser\fR\fR \- Provides full parser support for GRASS scripts.
.SH KEYWORDS
general, support, scripts
.SH SYNOPSIS
\fBg.parser \-\-help\fR
.br
\fBg.parser\fR [\-\fBs\fR] [\-\fBt\fR]  [\-\fBn\fR] \fIfilename\fR [\fIargument\fR,...]
.SS Flags:
.IP "\fB\-t\fR" 4m
.br
Print strings for translation
.IP "\fB\-s\fR" 4m
.br
Write option values to standard output instead of reinvoking script
.IP "\fB\-n\fR" 4m
.br
Write option values to standard output separated by null character
.SH DESCRIPTION
The \fIg.parser\fR 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.
.SH OPTIONS
Unless the \fB\-s\fR or \fB\-n\fR switch is used, the arguments are stored in
environment variables for use in your scripts. These variables are
named \(dqGIS_FLAG_<NAME>\(dq for flags and \(dqGIS_OPT_<NAME>\(dq for
options. The names of variables are converted to upper case. For
example if an option with key \fBinput\fR was defined in the script
header, the value will be available in variable \fBGIS_OPT_INPUT\fR
and the value of flag with key \fBf\fR will be available in variable
\fBGIS_FLAG_F\fR.
.PP
For flags, the value will be \(dq1\(dq if the flag was given, and \(dq0\(dq otherwise.
.PP
If the \fB\-s\fR or \fB\-n\fR switch is used, the options and flags are written to
standard output in the form \fIopt_<name>=<value>\fR and
\fIflag_<name>=<value>\fR, preceded by the string
\fB@ARGS_PARSED@\fR. If this string doesn\(cqt appear as the first line
of standard output, it indicates that the script was invoked with a switch such
as \fB\-\-html\-description\fR. In this case, the data written by
\fIg.parser\fR to standard output should be copied to the script\(cqs standard output
verbatim.
If the \fB\-s\fR switch is used, the options and flags are separated
by newlines. If the \fB\-n\fR switch is used, the options and flags
are separated by null characters.
.PP
Typical header definitions are as follows:
.br
.nf
\fC
#%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
\fR
.fi
With {NULL} it is possible to suppress a predefined description
or label.
.PP
The parsers allows using predefined \fIstandardized options and
flags\fR, see the list
of options and flags
in the programmer manual. Eg. the option
.br
.nf
\fC
#%option
#% key: raster
#% type: string
#% gisprompt: old,cell,raster
#% description: Raster input map
#% required: yes
#%end
\fR
.fi
can be easily defined as
.br
.nf
\fC
#%option G_OPT_R_MAP
#% key: raster
#%end
\fR
.fi
The parser allows defining predefined \fIrules\fR
for used options.
The syntax of the rules section is following:
.br
.nf
\fC
#%rules
#% exclusive: capfile_output, capfile
#%end
\fR
.fi
The parser also allows defining \(dqOR\(dq conditions, e.g. requiring raster
OR vector (for details, see below), e.g.for options:
.br
.nf
\fC
#%rules
#% required: raster, vector
#%end
\fR
.fi
and e.g., for flags:
.br
.nf
\fC
#%rules
#% required: \-i,\-d,\-c
#%end
\fR
.fi
.SH NOTES
An option can be instructed to allow multiple inputs by adding the
following line:
.br
.nf
\fC
#% multiple: yes
\fR
.fi
While this will only directly change the \fIUsage\fR section of the help
screen, the option\(cqs environmental string may be easily parsed from within
a script. For example, individual comma separated identities for an option
named \(dqinput\(dq can be parsed with the following Bash shell code:
.br
.nf
\fC
IFS=,
for opt in $GIS_OPT_INPUT ; do
    ... \(dq$opt\(dq
done
\fR
.fi
.PP
A \(dqguisection\(dq 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 \(dqRequired\(dq or \(dqOptions\(dq tab.  For example:
.br
.nf
\fC
#% guisection: tabname
\fR
.fi
would put that option in a tab named \fItabname\fR.
.PP
A \(dqkey_desc\(dq field may be added to each option to specify the text that
appears in the module\(cqs usage help section. For example:
.br
.nf
\fC
#% key_desc: filename
\fR
.fi
added to an \fBinput\fR option would create the usage summary
[input=filename].
.PP
If a script is run with \fB\-\-o\fR, the parser will
set GRASS_OVERWRITE=1, which has the same effect as passing
\fB\-\-o\fR to every module which is run from the script. Similarly, passing
\fB\-\-q\fR or \fB\-\-v\fR will set GRASS_VERBOSE to 0 or 3 respectively,
which has the same effect as passing \fB\-\-q\fR or \fB\-\-v\fR to every module which
is run from the script.  Rather than checking whether \fB\-\-o\fR, \fB\-\-q\fR or \fB\-\-v\fR
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 \fB\-\-o\fR, \fB\-\-q\fR or \fB\-\-v\fR being passed to the script or
set by other means.
.SH Conditional parameters
Marking an option as \(dqrequired\(dq will result in the parser raising a
fatal error if the option is not given, with one exception: if a flag
has the suppress_required option, and that flag is given, all
requirements are ignored. This feature is intended for flags which
abandon \(dqnormal operation\(dq for the module; e.g. \fIr.in.gdal\fR\(cqs
\fB\-f\fR flag (list supported formats) uses it.
.br
But in general, an option cannot be marked as required if it is
optional except for the special case of a suppress_required flag.
The parser has the ability to specify option relationships.
.PP
For C, the relevant functions are those in
lib/gis/parser_dependencies.c.
.PP
For scripts, relationships are specified using a \(dqrules\(dq section, e.g.
.br
.nf
\fC
#%rules
#% required: altitude,elevation
#%end
\fR
.fi
specifies that at least one of those options must be given. Both
options and flags can be specified (a leading \(dq\fB\-\fR\(dq denotes a flag).
The available rule types are:
.RS 4n
.IP \(bu 4n
exclusive: at most one of the options may be given
.IP \(bu 4n
required: at least one of the options must be given
.IP \(bu 4n
requires: if the first option is given, at least one of the
subsequent options must also be given
.IP \(bu 4n
requires_all: if the first option is given, all of the
subsequent options must also be given
.IP \(bu 4n
excludes: if the first option is given, none of the
subsequent options may be given
.IP \(bu 4n
collective: all or nothing; if any option is given, all
must be given
.RE
.SH AUTOMATED SCRIPT CREATION
The flag \fB\-\-script\fR added to a GRASS command, generates shell
output. To write out a \fIg.parser\fR boilerplate for easy
prototyping of Python scripts, the flag \fB\-\-script\fR can be added
to any GRASS command. Example:
.br
.nf
\fC
v.in.db \-\-script
\fR
.fi
.SH Help page template (HTML)
The flag \fB\-\-html\-description\fR added to a GRASS command
generates a related help page template in HTML. Example:
.br
.nf
\fC
v.in.db \-\-html\-description
\fR
.fi
.SH GUI window parser (XML)
The flag \fB\-\-interface\-description\fR added to a GRASS command
generates a related help page template in XML. Example:
.br
.nf
\fC
v.in.db \-\-interface\-description
\fR
.fi
.SH JSON
The flag \fB\-\-json\fR added to a GRASS command with parameters mandatorily
to be specified generates a module interface description in JSON. Example:
.br
.nf
\fC
v.in.db driver=sqlite database=mysqlite.db table=pointsfile x=x y=y z=z key=idcol out=dtmpoints \-\-json
{
  \(dqmodule\(dq: \(dqv.in.db\(dq,
  \(dqid\(dq: \(dqv.in.db_1804289383\(dq,
  \(dqinputs\(dq:[
     {\(dqparam\(dq: \(dqtable\(dq, \(dqvalue\(dq: \(dqpointsfile\(dq},
     {\(dqparam\(dq: \(dqdriver\(dq, \(dqvalue\(dq: \(dqsqlite\(dq},
     {\(dqparam\(dq: \(dqdatabase\(dq, \(dqvalue\(dq: \(dqmysqlite.db\(dq},
     {\(dqparam\(dq: \(dqx\(dq, \(dqvalue\(dq: \(dqx\(dq},
     {\(dqparam\(dq: \(dqy\(dq, \(dqvalue\(dq: \(dqy\(dq},
     {\(dqparam\(dq: \(dqz\(dq, \(dqvalue\(dq: \(dqz\(dq},
     {\(dqparam\(dq: \(dqkey\(dq, \(dqvalue\(dq: \(dqidcol\(dq}
   ],
  \(dqoutputs\(dq:[
     {\(dqparam\(dq: \(dqoutput\(dq, \(dqvalue\(dq: \(dqdtmpoints\(dq}
   ]
}
\fR
.fi
.SH Web Processing Service (WPS)
The flag \fB\-\-wps\-process\-description\fR added to a GRASS command
generates a Web Processing Service process description. Example:
.br
.nf
\fC
v.in.db \-\-wps\-process\-description
\fR
.fi
.SH reStructuredText
The flag \fB\-\-rst\-description\fR added to a GRASS command
generates module interface description in reStructuredText, a lightweight
markup language. Example:
.br
.nf
\fC
v.in.db \-\-rst\-description
\fR
.fi
reStructuredText is sometimes abbreviated as reST, ReST, or RST.
The commonly used file extension is .rst.
Don\(cqt be confused with Representational State Transfer (REST) technology.
.SH TRANSLATION
\fIg.parser\fR provides some support for translating the options of
scripts. If called with the \-t switch before the script filename like
this
.br
.nf
\fC
g.parser \-t somescriptfile
\fR
.fi
\fIg.parser\fR 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.
.SH EXAMPLES
All examples below autogenerate the graphical user interface when invoked
without parameters of flags:
.PP
.PP
To run properly, the script needs to be copied into a directory listed
in $GRASS_ADDON_PATH environmental variable with the
executable flag being set.
.PP
The script will provide a GUI (as above) and the following usage help
text:
.br
.nf
\fC
test.py|sh|pl \-\-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
\fR
.fi
.SS Example code for Python
.br
.nf
\fC
#!/usr/bin/env python3
# g.parser demo script for python programming
#%module
#% description: g.parser test script (python)
#% keyword: keyword1
#% keyword: keyword2
#%end
#%flag
#% key: f
#% description: A flag
#%end
#%option G_OPT_R_MAP
#% key: raster
#% required: yes
#%end
#%option G_OPT_V_MAP
#% key: vector
#%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[\(cqf\(cq]
    option1 = options[\(cqoption1\(cq]
    raster = options[\(cqraster\(cq]
    vector = options[\(cqvector\(cq]
    #### add your code here ####
    if flag_f:
        print \(dqFlag \-f set\(dq
    else:
        print \(dqFlag \-f not set\(dq
    # test if parameter present:
    if option1:
        print \(dqValue of option1 option: \(cq%s\(cq\(dq % option1
    print \(dqValue of raster option: \(cq%s\(cq\(dq % raster
    print \(dqValue of vector option: \(cq%s\(cq\(dq % vector
    #### end of your code ####
    return 0
if __name__ == \(dq__main__\(dq:
    options, flags = grass.parser()
    sys.exit(main())
\fR
.fi
.SS Example code for SHELL
.br
.nf
\fC
#!/bin/sh
# g.parser demo script for shell programming
#%module
#% description: g.parser test script (shell)
#%end
#%flag
#% key: f
#% description: A flag
#%end
#%option G_OPT_R_MAP
#% key: raster
#% required: yes
#%end
#%option G_OPT_V_MAP
#% key: vector
#%end
#%option
#% key: option1
#% type: string
#% description: An option
#% required: no
#%end
if [ \-z \(dq$GISBASE\(dq ] ; then
    echo \(dqYou must be in GRASS GIS to run this program.\(dq 1>&2
    exit 1
fi
if [ \(dq$1\(dq != \(dq@ARGS_PARSED@\(dq ] ; then
    exec g.parser \(dq$0\(dq \(dq$@\(dq
fi
#### add your code below ####
echo \(dq\(dq
if [ $GIS_FLAG_F \-eq 1 ] ; then
  g.message message=\(dqFlag \-f set\(dq
else
  g.message message=\(dqFlag \-f not set\(dq
fi
# test if parameter present:
if [ \-n \(dq$GIS_OPT_OPTION1\(dq ] ; then
    echo \(dqValue of GIS_OPT_OPTION1: \(cq$GIS_OPT_OPTION1\(cq\(dq
fi
g.message message=\(dqValue of GIS_OPT_option1: \(cq$GIS_OPT_option1\(cq\(dq
g.message message=\(dqValue of GIS_OPT_raster: \(cq$GIS_OPT_raster\(cq\(dq
g.message message=\(dqValue of GIS_OPT_vect: \(cq$GIS_OPT_vector\(cq\(dq
#### end of your code ####
\fR
.fi
.SS Example code for Perl
.br
.nf
\fC
#!/usr/bin/perl \-w
use strict;
# g.parser demo script
#%module
#%  description: g.parser test script (perl)
#%  keyword: keyword1
#%  keyword: keyword2
#%end
#%flag
#%  key: f
#%  description: A flag
#%end
#%option G_OPT_R_MAP
#% key: raster
#% required: yes
#%end
#%option G_OPT_V_MAP
#% key: vector
#%end
#%option
#% key: option1
#% type: string
#% description: An option
#% required: no
#%end
if ( !$ENV{\(cqGISBASE\(cq} ) {
    printf(STDERR  \(dqYou must be in GRASS GIS to run this program.\(rsn\(dq);
    exit 1;
}
if( $ARGV[0] ne \(cq@ARGS_PARSED@\(cq ){
    my $arg = \(dq\(dq;
    for (my $i=0; $i < @ARGV;$i++) {
        $arg .= \(dq $ARGV[$i] \(dq;
    }
    system(\(dq$ENV{GISBASE}/bin/g.parser $0 $arg\(dq);
    exit;
}
#### add your code here ####
print  \(dq\(rsn\(dq;
if ( $ENV{\(cqGIS_FLAG_F\(cq} eq \(dq1\(dq ){
   print \(dqFlag \-f set\(rsn\(dq
}
else {
   print \(dqFlag \-f not set\(rsn\(dq
}
printf (\(dqValue of GIS_OPT_option1: \(cq%s\(cq\(rsn\(dq, $ENV{\(cqGIS_OPT_OPTION1\(cq});
printf (\(dqValue of GIS_OPT_raster: \(cq%s\(cq\(rsn\(dq, $ENV{\(cqGIS_OPT_RASTER\(cq});
printf (\(dqValue of GIS_OPT_vect: \(cq%s\(cq\(rsn\(dq, $ENV{\(cqGIS_OPT_VECTOR\(cq});
#### end of your code ####
\fR
.fi
.SS Easy creation of a script
By using the \fB\-\-script\fR flag with any GRASS GIS module (must be run in
a GRASS GIS session) header, description, keywords, parameters, flags and
a template main Python script section will be printed in the terminal which
can be saved to a file and used for further script programming.
.PP
In this example, the module \fIv.what.rast\fR is used as an example.
The output is shown below:
.br
.nf
\fC
v.what.rast \-\-script
#!/usr/bin/env python3
############################################################################
#
# MODULE:       v.what.rast_wrapper
# AUTHOR(S):    username
# PURPOSE:      Wrapper for v.what.rast
# COPYRIGHT:    (C) 2017 by username, and the GRASS Development Team
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
############################################################################
#%module
#% description: Uploads raster values at positions of vector points to the table.
#% keyword: vector, sampling, raster, position, querying, attribute table, surface information
#%end
#%flag
#% key: i
#% description: Interpolate values from the nearest four cells
#%end
#%flag
#% key: p
#% description: Print categories and values instead of updating the database
#%end
#%option
#% key: map
#% type: string
#% required: yes
#% multiple: no
#% key_desc: name
#% label: Name of vector points map for which to edit attributes
#% description: Or data source for direct OGR access
#% gisprompt: old,vector,vector
#%end
#%option
#% key: layer
#% type: string
#% required: no
#% multiple: no
#% label: Layer number or name
#% description: Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
#% answer: 1
#% gisprompt: old,layer,layer
#%end
#%option
#% key: type
#% type: string
#% required: no
#% multiple: yes
#% options: point,centroid
#% description: Input feature type
#% answer: point
#%end
#%option
#% key: raster
#% type: string
#% required: yes
#% multiple: no
#% key_desc: name
#% description: Name of existing raster map to be queried
#% gisprompt: old,cell,raster
#%end
#%option
#% key: column
#% type: string
#% required: no
#% multiple: no
#% key_desc: name
#% description: Name of attribute column to be updated with the query result
#% gisprompt: old,dbcolumn,dbcolumn
#%end
#%option
#% key: where
#% type: string
#% required: no
#% multiple: no
#% key_desc: sql_query
#% label: WHERE conditions of SQL statement without \(cqwhere\(cq keyword
#% description: Example: income < 1000 and population >= 10000
#%end
import sys
import grass.script as grass
def main():
    # put code here
    return 0
if __name__ == \(dq__main__\(dq:
    options, flags = grass.parser()
    sys.exit(main())
\fR
.fi
.SH SEE ALSO
\fI
g.filename,
g.findfile,
g.tempfile
\fR
.PP
Overview table: Parser standard options
.PP
Submitting rules for Python
.PP
Related Wiki pages:
Using GRASS GIS with other programming languages
.SH AUTHOR
Glynn Clements
.SH SOURCE CODE
.PP
Available at: g.parser source code (history)
.PP
Main index |
General index |
Topics index |
Keywords index |
Graphical index |
Full index
.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual