.TH g.mapsets
.SH NAME
\fIg.mapsets\fR \- Modifies the user's current mapset search path,
affecting the user's access to data existing under the other GRASS mapsets
in the current location.
.br
\fI(GRASS File Management Program)\fR
.SH SYNOPSIS
\fBg.mapsets\fR
.br
\fBg.mapsets help\fR
.br
\fBg.mapsets \fR[\fB-lp\fR] [\fBmapset\*=\fIname\fR[,\fIname\fR,...]]
.SH DESCRIPTION
A \fImapset\fR holds a distinct set of data layers,
each relevant to the same (or a subset of the same) geographic region,
and each drawn in the same map coordinate system.
At the outset of every GRASS session, the user identifies a
GRASS data base, location, and mapset that are to be the
user's \fIcurrent data base\fR, \fIcurrent location\fR,
and \fIcurrent mapset\fR for the duration of the session;
any maps created by the user during the session
will be stored under the \fIcurrent mapset\fR ($MAPSET)
set at the session's outset.
.LP
The user can add, modify, and delete data layers that exist under his
\fIcurrent mapset\fR.  Although the user can also \fIaccess\fR
(i.e., use) data that are stored under \fIother\fR mapsets in the
same GRASS location, the user can only make permanent changes
(create or modify data) located in the \fIcurrent mapset\fR.
The user's \fImapset search path\fR lists the order in which other mapsets
in the same GRASS location can be searched and their data accessed
by the user.  The user can modify the listing and order in which
these mapsets are accessed by modifying the mapset search path;
this can be done using the \fIg.mapsets\fR command.
This program allows the user to use other's relevant map data without
altering the original data layer, and without taking up disk space
with a copy of the original map.
.LP
\fIg.mapsets\fR shows the user available mapsets under the current
GRASS location, lists mapsets to which the user currently has access,
and lists the order in which accessible mapsets will be accessed
by GRASS programs searching for data files.
The user is then given the opportunity to add or delete mapset names from
his search path, or modify the order in which mapsets will be accessed.
.LP
When the user specifies the name of a data base element file
(e.g., a particular vector file, raster file, imagery group file, etc.)
to a GRASS program, the program searches for the named file
under each of the mapsets listed in the user's mapset search path
in the order listed there until the program finds a file
of the given name.  (Users can also specify a file by
its mapset, to make explicit the mapset from which the file is to be
drawn;  e.g., the command:
.LP
.RS
\fBg.copy rast\*='soils.file@PERMANENT',my.soils\fB
.RE
.LP
ensures that a new file named \fImy.soils\fR is to be a copy of
the file \fIsoils.file\fR from the mapset PERMANENT.)
.LP
It is common for a user to have the special mapset
.B PERMANENT
included in his mapset search path, as this mapset typically contains
finished base maps relevant to many applications.
Often, other mapsets which contain sets of interpreted map layers
will be likewise included in the user's mapset search path.
Suppose, for example, that the mapset
.I Soil_Maps
contains interpreted soils map layers to which the user wants access.
The mapset
.I Soil_Maps
should then be included in the user's \fIsearch\ path\fR variable.
.LP
The \fImapset\ search\ path\fR is saved as part of the current mapset.
When the user works with that mapset in subsequent GRASS sessions,
the previously saved mapset search path will be used (and will continue
to be used until it is modified by the user with \fIg.mapsets\fR).
.bp
.LP
\fBFlags:\fR
.IP \fB-l\fR 18
List all available mapsets under the user's current location.
.IP \fB-p\fR 18
Print the user's current mapset search path to standard output.

.LP
\fBParameter:\fR
.IP "\fBmapset\*=\fIname\fR[,\fIname\fR,...]" 25
Name(s) of existing GRASS mapset(s) under the current location.
.LP
\fIg.mapsets\fR sets the current \fImapset\ search\ path\fR
to the \fImapsets\fR named on the command line.
If \fBg.mapsets\fR is typed but no \fImapset\fR names are specified by the
user on the command line, the program will print the user's current mapset
search path, list available mapsets, and prompt the user for a new mapset
search path listing.
.LP
The interactive version also is unique in allowing the user to 
incrementally add or subtract mapsets from the current mapset search path.
If the first symbol of the new mapset search path listing is a "+" followed
by a blank and a list of mapsets (or mapset numbers), these will be added to
the tail of the current search path.  Alternatively, a "-" can be used to
delete specified mapsets from the current search path.
.SH NOTES
Users can restrict others' access to their mapset files through
use of the GRASS program \fIg.access\fR.  Mapsets to which access
is restricted can still be listed in another's mapset search path;
however, access to these mapsets will remain restricted.
.SH SEE ALSO
.I g.access,
.I g.copy,
.I g.gisenv,
.I g.list
.SH "AUTHOR"
Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
