Running a QGIS processing model using qgis_process

Unleash QGIS Power from Your Command Line: A Human’s Guide to qgis_process

Okay, so you’re a QGIS whiz, right? You love the GUI, the plugins, the whole nine yards. But have you ever felt chained to your desktop when you just want to automate some spatial magic? That’s where qgis_process comes in – think of it as your secret weapon for unlocking QGIS processing from the command line. It’s like giving your GIS superpowers a serious upgrade!

Introduced back in QGIS 3.14 (Pi, yum!), qgis_process lets you run QGIS processing algorithms and models directly from your terminal. Forget clunky workarounds; this is pure, unadulterated command-line goodness. Perfect for scripting, batch jobs, or even sneaking QGIS smarts into other apps. Trust me, once you get the hang of this, you’ll wonder how you ever lived without it.

Decoding qgis_process: It’s Easier Than You Think

Basically, qgis_process is a command-line tool that lets you tap into QGIS processing power without actually needing the QGIS desktop app open. I know, mind-blowing, right?

The Magic Words: Essential Commands

qgis_process speaks your language (well, command-line language), and it’s got a few key phrases you need to know:

• qgis_process list: This is your “what’s on the menu?” command. It spits out a list of every algorithm available, neatly organized by provider (like the built-in QGIS goodies, or stuff from GDAL and SAGA). Seriously, run this first – you might discover tools you never knew existed!
• qgis_process plugins: This command lists all available and activated plugins that expose processing providers. Keep in mind that only plugins advertising the hasProcessingProvider metadata option are loaded by the tool.
• qgis_process help algid: Stuck? Need a hint? This command is your best friend. Just type qgis_process help followed by the algorithm’s ID (like native:buffer), and boom! You’ll get all the details on what it does and what parameters it needs.
• qgis_process run: This is where the rubber meets the road. This command actually runs an algorithm. You tell it which algorithm to use and what parameters to feed it, and it gets to work. For example, that buffer command I mentioned earlier? It might look something like this: qgis_process run native:buffer –INPUT=”my_shapefile.shp” –DISTANCE=20 –OUTPUT=”buffered.shp”. See? Not so scary!

Models: Your Secret Weapon for Complex Tasks

But wait, there’s more! qgis_process can also run entire processing models that you’ve built in the QGIS Model Designer. This is where things get really powerful. You can chain together a whole series of steps – clip, buffer, dissolve, calculate – all in one go. Think of the possibilities!

To run a model, just point qgis_process to your model file (.model3 extension) and tell it what values to use for the inputs.