Provided by: procmail_3.22-26_amd64 #### 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 allocate 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.

```

#### Weightedregularexpressionconditions

```       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.

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 exponentially.

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.

```

#### Weightedprogramconditions

```       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.

```

#### Weightedlengthconditions

```       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.

```

#### MISCELLANEOUS

```       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 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.

```

#### CAVEATS

```       Because  this  speeds  up the search by an order of magnitude, the procmail internal egrep
will always search for the leftmost 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:

.*     will always match a zero length string at the same spot.

.+     will always match one character (except newlines of course).

```

#### SEEALSO

```       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.

```

#### MISCELLANEOUS

```       As  soon  as  `plus  infinity' (2147483647) is reached, any subsequent 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<x<1,  the  total added score for this
condition will asymptotically approach:

w
-------
1 - x

In order to reach half the maximum value you need

- ln 2
n = --------
ln x

matches.

```

#### AUTHORS

```       Stephen R. van den Berg
<srb@cuci.nl>
Philip A. Guenther
<guenther@sendmail.com>
```