Looping with a variable r.mapcalc GRASS GIS

Question

I want to crop a raster based on another one, inside a loop. I created a mask (MASK) and then cropped the old raster (old), creating a new raster (new).

r.mask vector=EU@PERMANENT #my mask 
r.mapcalc "new = old" 

For a single raster, it works. However, I have many old rasters, and I want to create a loop. I tried this:

for i in `cat /myPath/myRasters.txt | tr -d '\r'`
do
echo SET REGION 
g.region vector=EU@PERMANENT
echo CREATE A MASK 
r.mask --o vector=EU@PERMANENT  
echo CROP $i RASTER 
r.mapcalc "$i'_new' = $i'_old'"
r.mask -r 
done 

I can see the problem is in the syntax used, as I get this ERROR message after echo CROP $i RASTER:

syntax error, unexpected STRING, expecting '('

I tried also to use r.mapcalc with:

"$i'_new' = $i'_old'"
'$i'_new' = $i'_old''
"${i}'_new' = ${i}'_old'"
"$i'_new' = if(MASK,$i'_old')"

this last one following r.mapcalc manual page ( https://grass.osgeo.org/grass82/manuals/r.mapcalc.html ), where it says

To mask raster map layer b by raster map layer a:
result = if(a,b)

and this: https://grasswiki.osgeo.org/wiki/Cropping_maps

But nothing works. Previous similar questions (e.g., Loop using variable - r.mapcalc GRASS GIS ) didnt' help. I am using GRASS 7.8.6 on Ubuntu 18.04.6 (from remote, I have Windows 10).

Answer 1

Following your answer in the comments, you have a text file with the raster names listed, row by row. So:

# Set region and mask once. No need to do this in the loop
echo "SET REGION" 
g.region vector=EU
echo "CREATE A MASK"
r.mask --o vector=EU

while read i; echo "CROP ${i}"; r.mapcalc "${i}_new = ${i}"; done < /myPath/myRasters.txt

r.mask -r   

That should do it.