Regex in script from variable using egrep

Question

I'm trying to parse the variable A_DESTINATION (a directory) and only call out the words in between the /.../

case "$TR_TORRENT_INFO" in
    *test1.com*)
    A_DESTINATION=${A_DESTINATION}/Books/
    ;;
    *test2.com*)
    A_DESTINATION=${A_DESTINATION}/Movies/
    ;;
    *test3.com*)
    A_DESTINATION=${A_DESTINATION}/Music/
    ;;
    *)
    A_DESTINATION=${A_DESTINATION}/Miscellaneous/
    ;;
esac

test="$(egrep '\/([^/.]+)\/$' $A_DESTINATION)"
echo test

I've gotten a regex in my script but it's not returning the folder successfully (i.e. in this case, /Miscellaneous/) in my log. It's just displaying this:

+ A_DESTINATION=/mnt/sda1/Miscellaneous/
+ egrep \/([^/.]+)\/$ /mnt/sda1/Miscellaneous/
+ test=
+ echo test
test

What am I doing wrong? Thanks!

Answer 1

Instead of adding a final directory suffix to $A_DESTINATION and then extracting it again with grep or whatever, why not just use a separate variable (e.g. $final) in the case statement and add that to $A_DESTINATION afterwards? For example:

case "$TR_TORRENT_INFO" in
    *test1.com*) final='Books' ;;
    *test2.com*) final='Movies' ;;
    *test3.com*) final='Music' ;;
              *) final='Miscellaneous' ;;
esac

A_DESTINATION="$A_DESTINATION/$final/"

echo "$final"

This works, is simpler and, IMO, is also easier to read.

BTW, the single-quotes around Books, Movies, etc aren't strictly necessary (because there are no spaces or shell metacharacters in the strings), but they don't hurt and IMO single-quoting fixed strings is a good-habit to get into. It's also a reminder to use single-quotes if you want to add another case with a space in the final directory name (e.g. maybe something like final='Other Junk' ;;)

Answer 2

Following steeldrive's suggestion of leaving off the trailing / in the assignments:

case "$TR_TORRENT_INFO" in
    *test1.com*) A_DESTINATION="$A_DESTINATION/Books"  ;;
    *test2.com*) A_DESTINATION="$A_DESTINATION/Movies" ;;
    *test3.com*) A_DESTINATION="$A_DESTINATION/Music"  ;;
    *) A_DESTINATION="$A_DESTINATION/Miscellaneous"
esac

... or use a variable to hold the added path element as cas suggests, which will be easier to read.

This will allow you to use either the basename utility or the ${parameter##word} parameter substitution to get at the final part of the path in $A_DESTINATION.

The basename of a pathname does not need to be a file. It's simply the last part of a path:

printf 'basename is "%s"\n' "${A_DESTINATION##*/}"

or

printf 'basename is "%s"\n' "$( basename "$A_DESTINATION" )"

When you later add a filename to the path, then include the / path separator:

filepath="$A_DESTINATION/$filename"

---

Your egrep command:

egrep '\/([^/.]+)\/$' $A_DESTINATION

This will instruct egrep to read $A_DESTINATION as a file and apply the given regular expression to it.

The following would have worked (assuming no trailing /), but you should use the above mentioned solution instead:

printf '%s\n' "$A_DESTINATION" | grep -o '[^/]*$'

---

Don't use test as the name of a variable as it is also the name of a standard command. There is no risk of "overloading" the command test, but it would potentially make the code confusing to read.