27.8. Using processing from the command line
QGIS comes with a tool called QGIS Processing Executor
which allows you to run
Processing algorithms and models (built-in or provided by plugins) directly
from the command line without starting QGIS Desktop itself.
From a command line tool, run qgis_process
and you should get:
QGIS Processing Executor - 3.35.0-Master 'Master' (3.35.0-Master)
Usage: C:\OSGeo4W\apps\qgis-dev\bin\qgis_process.exe [--help] [--version] [--json] [--verbose] [--no-python] [--skip-loading-plugins] [command] [algorithm id, path to model file, or path to Python script] [parameters]
Options:
--help or -h Output the help
--version or -v Output all versions related to QGIS Process
--json Output results as JSON objects
--verbose Output verbose logs
--no-python Disable Python support (results in faster startup)
--skip-loading-plugins Avoid loading enabled plugins (results in faster startup)
Available commands:
plugins list available and active plugins
plugins enable enables an installed plugin. The plugin name must be specified, e.g. "plugins enable cartography_tools"
plugins disable disables an installed plugin. The plugin name must be specified, e.g. "plugins disable cartography_tools"
list list all available processing algorithms
help show help for an algorithm. The algorithm id or a path to a model file must be specified.
run runs an algorithm. The algorithm id or a path to a model file and parameter values must be specified.
Parameter values are specified after -- with PARAMETER=VALUE syntax.
Ordered list values for a parameter can be created by specifying the parameter multiple times,
e.g. --LAYERS=layer1.shp --LAYERS=layer2.shp
Alternatively, a '-' character in place of the parameters argument indicates that the parameters should be read from STDIN as a JSON object.
The JSON should be structured as a map containing at least the "inputs" key specifying a map of input parameter values.
This implies the --json option for output as a JSON object.
If required, the ellipsoid to use for distance and area calculations can be specified via the "--ELLIPSOID=name" argument.
If required, an existing QGIS project to use during the algorithm execution can be specified via the "--PROJECT_PATH=path" argument.
When passing parameters as a JSON object from STDIN, these extra arguments can be provided as an "ellipsoid" and a "project_path" key respectively.
Note
Only installed plugins that advertise hasProcessingProvider=yes
in their metadata.txt
file are recognized and can be activated
or loaded by qgis_process tool.
Hint
Before calling qgis_process on a system without window manager (e.g. a headless server), you should set:
export QT_QPA_PLATFORM=offscreen
The command list
can be used to get a list of all available providers
and algorithms.
qgis_process list
The command help
can be used to get further information about commands or algorithms.
qgis_process help qgis:regularpoints
The command run
can be used to run an algorithm or model.
Specify the name of the algorithm or a path to a model as first parameter.
qgis_process run native:buffer -- INPUT=source.shp DISTANCE=2 OUTPUT=buffered.shp
Where a parameter accepts a list of values, set the same variable multiple times.
qgis_process run native:mergevectorlayers -- LAYERS=input1.shp LAYERS=input2.shp OUTPUT=merged.shp
While running an algorithm a text-based feedback bar is shown, and the operation can be cancelled via CTRL+C.
The run
command also supports further parameters.
--json
will format stdout output in a JSON structured way.--ellipsoid
will set the ellipsoid to the specified one.--distance_units
will use the specified distance units.--area_units
will use the specified area units.--project_path
will load the specified project for running the algorithm.
Complex input parameters, i.e. parameter types which are themselves specified
as a dictionary type object for algorithms, are supported by qgis_process.
To indicate that parameters will be specified via stdin,
the qgis_process command must follow the format (with a trailing -
in place of the usual arguments list).
qgis_process run algorithmId -
The JSON object must contain an “inputs” key, which is a map of the input parameter values. E.g.
echo "{'inputs': {'INPUT': 'my_shape.shp', 'DISTANCE': 5}}" | qgis_process run native:buffer -
Additionally, extra settings like the distance units, area units, ellipsoid and project path can be included in this JSON object:
{
'ellipsoid': 'EPSG:7019',
'distance_units': 'feet',
'area_units': 'ha',
'project_path': 'C:/temp/my_project.qgs'
'inputs': {'DISTANCE': 5, 'SEGMENTS': 8 ... }
}
Specifying input parameters via stdin implies automatically the JSON
output format for results.