I've taken over another programmer's code and need a little help with a simple shell script. The previous programmer wrote a script to descend down into a number of directories and make every file in the directory a symbolic link to a directory above it. There's one part, that although I'm positive is simple, I don't understand. Plus, I don't have a good resource for shell scripting, so I've come here. Here's the part the confuses me:

# The code cds into a directory a few lines before

for d in et00?
do
if [-d "$d" ]
then
echo Entering directory $d ...
cd $d
# rest of code

Based on where the shell script cds into, et001 et002 et003 et004 and et005 are five directories that match the et00?. There are other directories, but these would match if you were to create a regexp. Somehow this loop runs five times with $d equalling the directory names above on each pass.

This confuses me and I'll tell you why. I realize that ? is a wildcard and will match any character. However $d seems to somehow know that it's supposed to look at the directory structure and make matches on that. But it seems like steps are missing in the above code snippet. For example

for d in et00?
do
echo $d
done

prints out et001 et002 et003 et004 and et005. But what on earth is directing it to do a regexp match on the directories? Any help would be greatly appreciated.