Standards, Environments, and Macros PROCMAILSC(5)
NAME
procmailsc - procmail weighted scoring technique
SYNOPSIS
[*] w^x condition
DESCRIPTION
In addition to the traditional true or false conditions you
can specify on a recipe, you can use a weighted scoring
technique to decide if a certain recipe matches or not.
When weighted scoring is used in a recipe, then the final
score for that recipe must be positive for it to match.
A certain condition can contribute to the score if you allo-
cate it a `weight' (w) and an `exponent' (x). You do this
by preceding the condition (on the same line) with:
w^x
Whereas both w and x are real numbers between -2147483647.0
and 2147483647.0 inclusive.
Weighted regular expression conditions
The first time the regular expression is found, it will add
w to the score. The second time it is found, w*x will be
added. The third time it is found, w*x*x will be added.
The fourth time w*x*x*x will be added. And so forth.
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.
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Standards, Environments, and Macros PROCMAILSC(5)
0 L
will generate an additional score of:
1
/ M \
w * ---
\ L /
And:
* w^x < L
will generate an additional score of:
1
/ 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
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Standards, Environments, and Macros PROCMAILSC(5)
latter case, smaller mails will be favoured. Although x can
be varied to fine-tune the steepness of the function, typi-
cal usage sets x=1.
MISCELANEOUS
You can query the final score of all the conditions on a
recipe from the environment variable $=. This variable is
set every time just after procmail has parsed all conditions
on a recipe (even if the recipe is not being executed).
EXAMPLES
The following recipe will ditch all mails having more than
150 lines in the body. The first condition contains an
empty regular expression which, because it always matches,
is used to give our score a negative offset. The second
condition then matches every line in the mail, and consumes
up the previous negative offset we gave (one point per
line). In the end, the score will only be positive if the
mail contained more than 150 lines.
:0 Bh
* -150^0
* 1^1 ^.*$
/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 impor-
tant 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.
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Standards, Environments, and Macros PROCMAILSC(5)
:0 HB
* !^Precedence:.*(junkbulk)
* 2000^0 ^From:.*(john@homeclaire@work)
* 2000^0 ^Subject:.*meeting
* 300^0 ^Subject:.*Re:
* 1000^.75 elvispresley
* -100^1 ^>
* 350^.9 :-\)
* -500^0 ^From:.*(bossjanehenry)@work
* -100^3 > 2000
priorityfolder
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 origi-
nal 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:.*(paulabill)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.
CAVEATS
Because this speeds up the search by an order of magnitude,
the procmail internal egrep will always search for the left-
most shortest match, unless it is determining what to assign
to MATCH, in which case it searches the leftmost longest
match. E.g. for the leftmost shortest match, by itself, the
regular expression:
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Standards, Environments, and Macros PROCMAILSC(5)
.* will always match a zero length string at the same
spot.
.] will always match one character (except newlines of
course).
SEE ALSO
procmail(1), procmailrc(5), procmailex(5), sh(1), csh(1),
egrep(1), grep(1),
BUGS
If, in a length condition, you specify an x that causes an
overflow, procmail is at the mercy of the pow(3) function in
your mathematical library.
Floating point numbers in `engineering' format (e.g., 12e5)
are not accepted.
MISCELANEOUS
As soon as `plus infinity' (2147483647) is reached, any sub-
sequent weighted conditions will simply be skipped.
As soon as `minus infinity' (-2147483647) is reached, the
condition will be considered as `no match' and the recipe
will terminate early.
NOTES
If in a regular expression weighted formula 0
Philip A. Guenther
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
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Standards, Environments, and Macros PROCMAILSC(5)
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWprocmail
Interface Stability Committed
NOTES
Source for procmail is available on http:/opensolaris.org.
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