A certain condition can contribute to the score if you allocate it a `weight' (w) and an `exponent' (x). You do this by preceding the condition (on the same line) with:
This can be described by the following concise formula:
n
n k-1 x - 1
w * Sum x = w * -------
k=1 x - 1
It represents the total added score for this condition if n matches are found.
Note that the following case distinctions can be made:
| x=0 | Only the first match will contribute w to the score. Any subsequent matches are ignored. |
| x=1 | Every match will contribute the same w to the score. The score grows linearly with the number of matches found. |
| 0<x<1 | Every match will contribute less to the score than the previous one. The score will asymptotically approach a certain value (see the NOTES section below). |
| 1<x | Every match will contribute more to the score than the previous one. The score will grow exponen- tionally. |
| x<0 | Can be utilised to favour odd or even number of matches. |
If the regular expression is negated (i.e. matches if it isn't found), then n obviously can either be zero or one.
Weighted program conditions
If the program returns an exitcode of EXIT_SUCCESS (=0),
then the total added score will be w. If it returns any
other exitcode (indicating failure), the total added score
will be x.
If the exitcode of the program is negated, then, the exitcode will be considered as if it were a virtual number of matches. Calculation of the added score then proceeds as if it had been a normal regular expression with n=`exitcode' matches.
Weighted length conditions
If the length of the actual mail is M then:
* w^x > L
will generate an additional score of:
x
/ M \
w * | --- |
\ L /
And:
* w^x < L
will generate an additional score of:
x
/ L \
w * | --- |
\ M /
In both cases, if L=M, this will add w to the score. In the former case however, larger mails will be favoured, in the latter case, smaller mails will be favoured. Although x can be varied to fine-tune the steepness of the function, typical usage sets x=1.
:0 Bh
* -150^0
* 1^1 ^.*$
/dev/null
Suppose you have a priority folder which you always read first. The next recipe picks out the priority mail and files them in this special folder. The first condition is a regular one, i.e. it doesn't contribute to the score, but simply has to be satisfied. The other conditions describe things like: john and claire usually have something important to say, meetings are usually important, replies are favoured a bit, mails about Elvis (this is merely an example :-) are favoured (the more he is mentioned, the more the mail is favoured, but the maximum extra score due to Elvis will be 4000, no matter how often he is mentioned), lots of quoted lines are disliked, smileys are appreciated (the score for those will reach a maximum of 3500), those three people usually don't send interesting mails, the mails should preferably be small (e.g. 2000 bytes long mails will score -100, 4000 bytes long mails do -800). As you see, if some of the uninteresting people send mail, then the mail still has a chance of landing in the priority folder, e.g. if it is about a meeting, or if it contains at least two smileys.
:0 HB
* !^Precedence:.*(junk|bulk)
* 2000^0 ^From:.*(john@home|claire@work)
* 2000^0 ^Subject:.*meeting
* 300^0 ^Subject:.*Re:
* 1000^.75 elvis|presley
* -100^1 ^>
* 350^.9 :-\)
* -500^0 ^From:.*(boss|jane|henry)@work
* -100^3 > 2000
priority_folder
If you are subscribed to a mailinglist, and just would like to read the quality mails, then the following recipes could do the trick. First we make sure that the mail is coming from the mailinglist. Then we check if it is from certain persons of whom we value the opinion, or about a subject we absolutely want to know everything about. If it is, file it. Otherwise, check if the ratio of quoted lines to original lines is at most 1:2. If it exceeds that, ditch the mail. Everything that survived the previous test, is filed.
:0
^From mailinglist-request@some.where
{
:0:
* ^(From:.*(paula|bill)|Subject:.*skiing)
mailinglist
:0 Bh
* 20^1 ^>
* -10^1 ^[^>]
/dev/null
:0:
mailinglist
}
For further examples you should look in the procmailex(5) man page.
| .* | will always match a zero length string at the same spot. |
| .+ | will always match one character (except newlines of course). |
As soon as `minus infinity' (-2147483647) is reached, the condition will be considered as `no match' and the recipe will terminate early.
w
-------
1 - x
In order to reach half the maximum value you need
- ln 2
n = --------
ln x
matches.