For loop inside another doesn't work #! /bin/bash for (( l = 1 ; l <= 50; ++l )) ; do for (( k = 1 ; k <= 1000; ++k )) ; do sed -n '$l,$lp' $k.dat >> ~/Escritorio/$l.txt done done The script is located in a folder together with 1000 dat files each one having 50 lines of text. The dat files are called `1.dat`, `2.dat`,...., `1000.dat` My purpose is to make files `l.txt`, where `l.txt` has the l line of `1.dat`, the l line of `2.dat`, etc. For that, I use the `sed` command to select the l file of each dat file. But when I run the above script, the txt created have nothing inside... Where is the mistake?

for LINE in {1..50}; do
for FILE in {1..1000}; do
sed -n "${LINE}p" "${FILE}.dat" >>"~/Escritorio/${LINE}.dat"
done
done


In your script you are using single quotes for the sed expression, variables don't expand inside single quotes, you need to use double quotes.

Also there is a one liner with awk that can do the same:


awk 'FNR<=50 {filename=sprintf("results/%d.dat", FNR); print >> filename; close(filename)}' *.dat


Just create the results directory, or change it in the command to another one, `~` does not expand to home there.