on January 6, 2023

Call QGIS geoprocessing tools from command line (terminal, bash-script)

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Unleash the Power of QGIS Geoprocessing from the Command Line (No Coding Degree Required!)

QGIS. It’s a powerhouse of open-source GIS goodness. You probably know it for its user-friendly interface, but did you know there’s a secret weapon hidden inside? I’m talking about the ability to run its geoprocessing tools directly from the command line. Yep, that terminal window you might usually associate with hardcore programmers can actually become your best friend for automating GIS tasks. Trust me, it’s not as scary as it sounds, and the payoff is huge.

Why Bother with the Command Line?

Okay, so why ditch the comfy GUI? Simple: it’s all about efficiency and control. Imagine you have a mountain of data to process – think hundreds of shapefiles that all need the same buffer applied. Doing that manually? Forget about it! With a little command-line magic, you can automate the whole thing. Plus, you can run these processes on servers without a graphical interface, schedule tasks for overnight processing, and weave QGIS geoprocessing into your existing scripts. Think of it as giving your GIS superpowers.

Enter qgis_process: Your New Best Friend

QGIS 3.14 was a game-changer because it introduced qgis_process. This command-line tool lets you tap into pretty much any processing algorithm QGIS has to offer, whether it’s built-in or comes from a plugin. Big thanks to Nyall Dawson and the Swedish User Group for making this happen! It’s like having the entire QGIS toolbox at your fingertips, ready to be unleashed with a few keystrokes.

Let’s Get Our Hands Dirty

  • Finding qgis_process:

    • Linux: You’re in luck! It’s probably already in your terminal’s path. Just type qgis_process and see what happens.
    • Windows: Head to the OSGeo4W shell (it comes with QGIS). The qgis_process executable lives in the OSGeo4W bin directory (something like C:\OSGeo4W\bin). You might need to run a .bat file first to get everything set up correctly. It’s a bit of a Windows quirk, but don’t worry, it’s usually straightforward.
    • Mac: You might need to specify the full path to the qgis_process utility.

  • Peeking at Available Algorithms:

    Curious about what you can do? Type this into your terminal:

    bash

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