Does Procmail have a lowercase function, or a similar capability?

Question

I'm using the following (classic) procmail recipe to catch mailing list e-mails and file them into a folder by list name:

:0
* ^((List-Id|X-(Mailing-)?List):(.*[<]\/[^>]*))
{
    LISTID=$MATCH
    :0
    * LISTID ?? ^\/[^@\.]* 
    Lists/$MATCH/
}

The problem is: if a list name changes from all lowercase to Firstlettercap, I end up with two folders, one for 'listname' and another for 'Listname'.

I'd like to lowercase the $MATCH variable before using it in the final delivery rule, but I'm not able to find a reference to a lc() function, or a regex/replacement that can be used to do this.

One comment below suggested this:

:0
 * ^((List-Id|X-(Mailing-)?List):(.*[<]\/[^>]*))
 {
    LISTID=`echo "$MATCH" | tr A-Z a-z`
    :0
    * LISTID ?? ^\/[^@\.]*
    .Lists.$MATCH/
 }

Which also doesn't appear to do what I'm after. Though, looking at it now, clearly the transliteration is only happening on the first occurrence of $MATCH and my guess is that it's not changing it at all for the use in the folder assignment line.

UPDATE #1: If I try to use LISTID in the folder assignment line, I get something like 'Bricolage.project.29601.lighthouseapp' instead of just 'Bricolage' or -- what I'm after -- just 'bricolage'.

Answer 1

Procmail itself has no functionality to replace text with other text. You can run the match through tr, or if avoiding external processes is really important, create a rule for each letter you need to map.

LISTID=`echo "$LISTID" | tr A-Z a-z`

# or alternatively
:0D
* LISTID ?? ^A\/.*
{ LISTID="a$MATCH" }
:0D
* LISTID ?? ^B\/.*
{ LISTID="b$MATCH" }
# ... etc

You could combine this with the final MATCH processing but I leave it at this for purposes of clarity.

Answer 2

AFAIK procmail regular expressions are always case INsensitive anyway, so you already get what you want without doing anything special. At least I always used it that way, and all the sites with procmail documentation I checked (3+) said so too.