Remove all letters between two underscores with shell script

Question

My directory has a list of filenames similar to _3vaca3424434_1-lecture-introduction.pdf and I want to rename it as 1-lecture-introduction.pdf. How can I do that?

Answer 1

for f in *; do
    new_f=${f##_*_}
    echo mv -- "$f" "$new_f"
done

Review the output of the above, and if the commands look right, remove the echo and run again.

${f##_*_} removes the longest prefix matching the pattern _*_ from the value of $f.