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To insert this function to my program I want to know what is command line executed by the algorithm "Merge vector layers" using QGIS GUI.

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After you run an algorithm from the Processing Toolbox, you can go to Processing -> History... -> ALGORITHM and you'll find the Python command to call the algorithm with the parameters you specified via GUI. For instance:

processing.runalg("qgis:mergevectorlayers",
                  "/docs/geodata/AMAZONAS.shp;/docs/geodata/PUTUMAYO.shp",
                  "/docs/merged.shp")

You would need to import the processing module before running the algorithm from the QGIS Python Console:

import processing
processing.runalg("qgis:mergevectorlayers",
                  "/docs/geodata/AMAZONAS.shp;/docs/geodata/PUTUMAYO.shp",
                  "/docs/merged.shp")

It's very helpful to understand the parameters of the algoritm, which you can achieve by following @DIVAD's recommendation.

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  • I'm searching for a shell command line (like ogr2ogr, grass...). I'v try most of them I didn't find one witch satisfy my needs :( . I want to merge tow vector files (polygons) with keeping the attribute table of the fist one and later dissolve the polygons witch overly
    – Mounirsky
    Nov 25, 2016 at 10:31
  • Here you find how to merge 2 Shapefiles with OGR. However, The PyQGIS command I put in my answer can also run in the OS console, as a standalone script, without opening QGIS GUI. Would be that OK for your use case?
    – Germán Carrillo
    Nov 25, 2016 at 12:39
  • The purpose is to dissolve polygons from layer1 witch overlap with polygons of layer2 keeping attributes table of layer1 and using a shell command line. can you please help me to do that ?
    – Mounirsky
    Nov 28, 2016 at 14:13
  • @Mounirsky - I would suggest asking a new question and expand on the details which you mentioned in your last comment. You should also accept an answer provided to you by clicking the green-faded tick on the left-hand side of the answer you feel solved your initial problem :)
    – Joseph
    Nov 29, 2016 at 12:15
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You can find all algorithms by typing processing.alglist().

You want to search for merging layers so type processing.alglist("merge").

Then choose one you need, e. g. processing.alghelp("qgis:mergevectorlayers") for more information.

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  • The purpose is to dissolve polygons from layer1 witch overlap with polygons of layer2 keeping attributes table of layer1 and using a shell command line. can you please help me to do that ?
    – Mounirsky
    Nov 28, 2016 at 14:13

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