r.external.out(1grass)

📦
version 8.5.0 · 12 versions
, in ubuntu stonking

💖 r.external.out — the manual page, but make it make sense 💖

okay so bestie, you know how GRASS normally hoards all your raster maps in its own lil format inside the mapset? Yeah. This module is the glow-up that says "nah, we're writing those out as actual files using GDAL instead." r.external.out is genuinely iconic for that. ✨

🎀 NAME 🎀

r.external.out — redirects raster output to a file utilizing the GDAL library rather than storing it in GRASS raster format. periodt. 💅

🏷️ KEYWORDS 🏷️

raster, export, output, external — that's the vibe check, those are the tags. 🌸

📜 SYNOPSIS 📜

r.external.out
r.external.out --help
r.external.out [-frp] directory=path  [extension=string]  format=string
[options=string[,string,...]]   [--help]  [--verbose]  [--quiet]  [--ui]

🚩 Flags (the little toggles, no cap) 🚩

  • -f — list all the supported formats and then dip. that's it, that's the whole flag. ✨
  • -r — stop using GDAL and go back to native output. the "we're so back" flag. revert era. 💫
  • -p — print the current status so you can see what's going on rn. 👀
  • --help — print the usage summary, bestie needs a lil reminder sometimes 🫶
  • --verbose — verbose module output, it's giving chatty 💬
  • --quiet — quiet module output, it's giving mysterious 🤫
  • --ui — force launch the GUI dialog, for the visual learners among us 🖥️

🧸 Parameters (the actual inputs, your main character args) 🧸

  • directory=path [required] — name of the output directory. yes it's required, no you can't skip it 🙈
  • extension=string — the extension for your output files. cute lil suffix 🎀
  • format=string [required] — the format of your output files. pick your fighter (full roster below):

Options: GTiff, COG, VRT, NITF, HFA, AAIGrid, DTED, PNG, JPEG, MEM, GIF, FITS, BMP, PCIDSK, PCRaster, ILWIS, SRTMHGT, Leveller, Terragen, netCDF, HDF4Image, ISIS3, PDS4, VICAR, ERS, JP2OpenJPEG, GRIB, RMF, WMS, RST, GSAG, GSBG, GS7BG, KMLSUPEROVERLAY, WEBP, PDF, MBTiles, CALS, WMTS, MRF, PNM, BT, LCP, GTX, KRO, ROI_PAC, RRASTER, BAG, S102, S104, S111, NWT_GRD, PostGISRaster, SAGA, XYZ, HF2, ZMap, SIGDEM, AVIF, HEIF, JPEGXL, GPKG, OpenFileGDB, NGW, ENVI, EHdr, ISCE, Zarr, MiraMonRaster — that's the whole alphabet of formats fr fr 🔥

  • options=string[,string,...] — creation options. you can pass a whole lil comma-separated stack of them ⭐

🌈 DESCRIPTION 🌈

r.external.out straight up tells GRASS: bestie, from now on, every raster map you generate? Write it out as a data file (think GeoTIFF) using GDAL, not as a GRASS raster format file in the current mapset. new rule, we're doing it this way now. 💅

And the way that any brand-new raster map is immediately written out through GDAL as a file? iconic behaviour honestly. no queue, no waiting, it just goes. ✨

📝 NOTES 📝

okay this part matters so listen up bestie:

  • A relative directory path (that's the directory parameter) gets interpreted relative to the current mapset directory — not the current directory where you launched the command. sneaky, right? 😭
  • If the directory is unspecified or empty (which, btw, happens if you just pass a simple filename for output), then your output file lands in the "gdal/" subdirectory of the current mapset directory. so it still ends up somewhere, just not where you'd guess. 🫶

🌟 EXAMPLES 🌟

Storing results from raster data analysis directly as GeoTIFF 💾

So r.external.out is the module you use to write out processing results directly in GeoTIFF format — and btw, any GDAL supported format can be used here, not just GeoTIFF. slay. 🌈

# define output directory for files resulting from GRASS calculation(s)
# and target format:
mkdir $HOME/gisoutput/
# hint: the create options are not mandatory
r.external.out directory=$HOME/gisoutput/ format="GTiff" option="BIGTIFF=YES,COMPRESS=DEFLATE"
# prepare sample analysis
g.region raster=elevation -p
# perform GRASS calculation (here: filter by height, write > 120m, NULL otherwise)
# this will store the output map directly as GeoTIFF, so we use .tif extension:
r.mapcalc "elev_filt.tif = if(elevation > 120.0, elevation, null() )"
# ...the "elev_filt.tif" is immediately written.
# cease GDAL output connection and turn back to write out GRASS raster files:
r.external.out -r
# verify resulting file
gdalinfo $HOME/gisoutput/elev_filt.tif

Complete workflow using only external geodata while processing in GRASS 🦋

r.external.out also teams up with r.external — so you can process external geodata inside GRASS while writing the results out directly in GeoTIFF. dream team fr. 🫶

# register GeoTIFF file to be used in current mapset:
r.external input=terra_lst1km20030314.LST_Day.tif output=modis_celsius
# define output directory for files resulting from GRASS calculation:
r.external.out directory=$HOME/gisoutput/ format="GTiff"
# perform GRASS calculation (here: extract pixels > 20 deg C)
# this stores the output map directly as GeoTIFF:
r.mapcalc "warm.tif = if(modis_celsius > 20.0, modis_celsius, null() )"
# cease GDAL output connection and turn back to write out GRASS raster files:
r.external.out -r
# now use the resulting file elsewhere
gdalinfo $HOME/gisoutput/warm.tif

🔗 REFERENCES 🔗

👀 SEE ALSO 👀

r.in.gdal, r.out.gdal, r.external — the whole squad, go check them out too 💜

👑 AUTHOR 👑

Glynn Clements — the legend responsible for this one. we stan. 🫡

💻 SOURCE CODE 💻

Available at: r.external.out source code (history) — go peek if you're nosy, no judgement 🌸

Latest change: Thursday Dec 04 09:43:11 2025 in commit: 8b4d7c3e310ec3122a5e870e724c50bd716f9513

Main index | Raster index | Topics index | Keywords index | Graphical index | Full index

okay and that's the whole page bestie!! 🎀 © 2003-2026 GRASS Development Team, GRASS 8.5.0 Reference Manual — this was r.external.out(1grass) from the GRASS 8.5.0 era, last touched Thursday Dec 04 09:43:11 2025 in that commit 8b4d7c3e310ec3122a5e870e724c50bd716f9513. now go write some GeoTIFFs and slay 💅✨🦋

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