Cfrtjryk

I have a folder with file-names ending .TIF, and I did a for loop

for i in *.TIF

In the loop, I want to get two types of files ending for example (B4.TIF and B5.TIF.

I did it like this but, it doesn't get the last four letters of the file name, instead it adds them at the end.

do ...... ${i}_B4.TIF -B ${i}_B5.TIF

My desired results are to get those file names in order to do some calculations

these are the examples of the files in the folder

LC08_L1TP_195020_20170224_20170301_01_T1_B4.TIF  

LC08_L1TP_195020_20171107_20171121_01_T1_B4.TIF



LC08_L1TP_195020_20170224_20170301_01_T1_B5.TIF  

LC08_L1TP_195020_20171107_20171121_01_T1_B5.TIF

and this is the script I am using to do the calculations

for i in *.TIF   

do 

    gdal_calc.py -A ${i}_B4_SA.TIF -B ${i}_B5_SA.TIF --type=Float32

--outfile=~/Geodata/goteborg/croped/ndvi/${i}_NDVI.TIF --calc="(B-A)/(B+A)"



done

The final output will be subtracting the B4 and B5. so this ${i}_B4_SA.TIF -B ${i}_B5_SA.TIF should get the two file names like this:

LC08_L1TP_195020_20170224_20170301_01_T1_B4.TIF - 

LC08_L1TP_195020_20170224_20170301_01_T1_B5.TIF

Loop over the files that constitute one half of the pairs, and for each such file, construct the filename of the corresponding pair and of the output file:

for b4_file in ./*_B4.TIF; do

    b5_file="${b4_file%_B4.TIF}_B5.TIF"

    ndvi_file="$HOME/Geodata/goteborg/croped/ndvi/${b4_file%_B4.TIF}_NDVI.TIF"



    if [ ! -f "$b5_file" ]; then

        printf 'Expected to find "%s" to go with "%s", but did notn' "$b5_file" "$b4_file" >&2

        continue

    fi



    # do whatever it is you need to do with "$b4_file" and "$b5_file"



    gdal_calc.py -A "$b4_file" -B "$b5_file" --type=Float32 

        --outfile="$ndvi_file --calc="(B-A)/(B+A)"



done

First note there is no-such thing as a file extension on Unix. . is just another character. So here I search for some ½ of your files, strip the end of the name off, ready to put it back on (in two different ways).

This will sort of work, but may have some latent bugs.

for f in *_B5.TIF   

do 

    i="$(echo "$f" | sed -r -e 's/(.*)_B5.TIF/1/')"

    … ${i}_B4_SA.TIF -B ${i}_B5_SA.TIF …

done

This should be more robust

find . -iname "*_B5.TIF" -print0 | sed -0r -e 's/(.*)_B5.TIF/1/' | xargs -0 -i … {}_B4_SA.TIF -B {}_B5_SA.TIF …

Please test, as I have not (may be some small error). And there is no error checking. Your program must check for miss-matches.

As you're using Bash, you can use Parameter expansion to chop the ending and save the common part of the filename in a new variable:

for f in *_B4.TIF ; do

    i="${f%_B4.TIF}"

    gdal_calc.py -A "${i}_B4.TIF" -B "${i}_B5.TIF" --outfile=".../${i}_NDVI.TIF"

done