Flags:

-f

List supported formats and exit

-r

Cease using OGR/PostGIS, revert to native output and exit

-p

Print current status

-g

Print current status in shell script style

--overwrite

Allow output files to overwrite existing files

--help

Print usage summary

--verbose

Verbose module output

--quiet

Quiet module output

--ui

Force launching GUI dialog

Parameters:

output=string

Name of output directory or OGR or PostGIS data source
Examples:
        ESRI Shapefile: directory containing a shapefile
        MapInfo File: directory containing a mapinfo file
        PostGIS database: connection string, eg. ’PG:dbname=db user=grass’

format=string

Format for output vector data
Options: AmigoCloud, BAG, CSV, Carto, DGN, DXF, ESRI_Shapefile, Elasticsearch, FlatGeobuf, GML, GPKG, GPSBabel, GPX, GeoJSON, GeoJSONSeq, GeoRSS, JML, JSONFG, KML, LIBKML, MBTiles, MEM, MVT, MapInfo_File, MapML, MiraMonVector, NGW, ODS, OGR_GMT, OpenFileGDB, PCIDSK, PDF, PDS4, PGDUMP, PMTiles, PostgreSQL, S57, SQLite, Selafin, VDV, VICAR, WAsP, XLSX, netCDF
Default: ESRI_Shapefile

options=string[,string,...]

Creation options
Examples:
        ’SHPT=POINTZ’: create 3D point Shapefile data
        ’GEOM_TYPE=geography’: use geography PostGIS data
        ’SCHEMA=grass’: create new PostGIS tables in ’grass’ schema

loadsettings=name

Name of input file to read settings from

savesettings=name

Name for output file where to save current settings

PostgreSQL/PostGIS Creation Options

Note that built-in GRASS-PostGIS data provider (format=PostgreSQL) supports different creation options compared to PostgreSQL/PostGIS driver from OGR library:

ESRI Shapefile

v.external.out can be used along with v.external to process external geodata in GRASS while writing out the results directly eg. in ESRI Shapefile format:

# register Shapefile in GRASS mapset:
v.external input=/path/to/shapefiles layer=cities
# define output directory for GRASS calculation results:
v.external.out output=$HOME/gisoutput
# do something (here: spatial query), write output directly as Shapefile
v.select ainput=cities atype=point binput=forests btype=area operator=within output=fcities

Current settings can be printed using -p or -g flag.

v.external.out -p
output: /path/to/home/gisoutput
format: ESRI Shapefile

PostGIS (simple features)

PostGIS data can be accessed directly using GRASS-PostGIS data provider (GRASS must be compiled with PostgreSQL support).

# register PostGIS table in GRASS mapset:
v.external output=PG:dbname=gisdb layer=cities
# define output PostGIS database for GRASS calculation results stored as simple features:
v.external.out output=PG:dbname=gisdb format=PostgreSQL
# do some processing...

Note: If the environment variable GRASS_VECTOR_OGR is defined, or GRASS is compiled without PostgreSQL support then GRASS will use PostgreSQL driver from OGR library for reading and writing PostGIS data.

PostGIS Topology

# define output PostGIS database for GRASS calculation results stored as topological elements:
v.external.out output=PG:dbname=gisdb format=PostgreSQL options=topology=YES
# do some processing...

Note: PostGIS topological access is supported only in built-in GRASS-PostGIS data provider.

GRASS native format

To restore original settings, ie. use the GRASS native format, type:

v.external.out -r

Restore settings

Current settings can be stored to file by specifying output option.

# define output PostGIS database for GRASS calculation with
# results stored as topological elements:
v.external.out output=PG:dbname=gisdb format=PostgreSQL \


  options=topology=YES savesettings=gisdb_topo.txt
# ... and do some processing in PostGIS Topology

Back to native format:

v.external.out -r
# do some processing in native format

Restore previous settings from "gisdb_topo.txt" file by specifying loadsettings option.

v.external.out loadsettings=gisdb_topo.txt
# ... and do some processing in PostGIS Topology