Problem with Bash loop in GRASS GIS

Question

I'm new to GRASS GIS and programming and I'm running into a lot of what I imagine are beginners problems and something similar to this has been asked before, but not In a way that I understand.

I'm trying to bash import tif. files and tried (from GRASS GIS 6 tutorial https://grasswiki.osgeo.org/wiki/GRASS_6_Tutorial/Raster_data_management):

for file in `ls *.tif`
 do
 r.in.gdal input=$file output=${file%.tif}
done

but I get

File "<input>", line 1
 for file in `ls *.tif`
 ^
SyntaxError: invalid syntax

Since I'm new to programming world I have no idea how to fix this.

Answer 1

The answer above, in accordance with the title of your question, refers to scripting in a bash shell. (Not python). If you would like more information on bash scripting, have a look at this tutorial (referred from the GRASS bash scripting wiki page

If you want to work in python, then the language is quite different. For example, to loop thru a directory of *.tif files in python might go:

import os,glob
for tif_file in glob.glob("*.tif"):
 new_rast = os.path.splitext(tif_file)[0] 
 grass.run_command('r.in.gdal', input=tif_file, output=new_rast)

So, first choose your tools :-)

• Adam H: ok, thanks both of you, very helpful answers for a beginner, helped me towards a better understanding of these programming languages. I'm trying to use python for now, trying to figure all this out.

Answer 2

The proper syntax is:

for file in $(ls *.tif); do r.in.gdal input=$file output=${file%.tif}; done;

Where you gather the individual values provided by ls and iterate through them, so you have to put a variable sign($) before the ls command and put it between brackets.

When you call for the file variable later, you can either call for $file as in the input parameter or call a function to it, like the stripping function with the braces. If you call it in a function, you have to put a semicolon after, because in bash, the semicolon signs the end of a function/command.

• Adam H: I still get an syntax error, only know it points at the $ sign.
• Gabor Farkas: What is the full code, you're getting the syntax error for? For me, typing the code above in the GRASS terminal works fine.
• Adam H: Well, i'm still trying to figure out what to put in the code, I haven't figured out what basic thing to put in a code, like what would precede this syntax. I just put the syntax in the python terminal in grass.
• Nikos Alexandris: The proper syntax, for the first part of the loop command is: for file in *.tif. The ls command is neither needed nor correct, I think. For more read gnu.org/software/bash/manual/html_node/….