Set mtime based on date string in filename

Question

Given a group of files with the following naming convention:

datetime_restofname.txt

an example of which would be:

200906290700_somewordorphrase.txt

how could I batch change the mtime of the files to match the date and time in the filename?

Answer 1

$ for f in *.txt; do touch -t `echo $f | cut -f1 -d _` "$f"; done

This will set the file modtime to the date string before the underscore.