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13.4 mailavg - Check Size of Mailboxes

Contributed by Wes Morgan

While tuning our mail system, we needed to take a "snapshot" of the users' mailboxes at regular intervals over a 30-day period. This script simply calculates the average size and prints the arithmetic distribution of user mailboxes.

#! /bin/sh
#
# mailavg - average size of files in /usr/mail
#
# Written by Wes Morgan, morgan@engr.uky.edu, 2 Feb 90
ls -Fs /usr/mail | awk '
   { if(NR != 1) {
       total += $1; 
       count += 1;
       size = $1 + 0; 
       if(size == 0) zercount+=1;
       if(size > 0 && size <= 10) tencount+=1;
       if(size > 10 && size <= 19) teencount+=1;
       if(size > 20 && size <= 50) uptofiftycount+=1;
       if(size > 50) overfiftycount+=1;
       }
   }
   END { printf("/usr/mail has %d mailboxes using %d blocks,",
            count,total) 
         printf("average is %6.2f blocks\n", total/count)
         printf("\nDistribution:\n")
         printf("Size      Count\n")
         printf(" O           %d\n",zercount)
         printf("1-10         %d\n",tencount)
         printf("11-20        %d\n",teencount)
         printf("21-50        %d\n",uptofiftycount)
         printf("Over 50      %d\n",overfiftycount)
       }'
exit 0

Here's a sample output from mailavg :

$ 

mailavg


/usr/mail has 47 mailboxes using 5116 blocks,
average is 108.85 blocks
Distribution:
Size      Count
 O           1
1-10         13
11-20        1
21-50        5
Over 50      27

13.4.1 Program Notes for mailavg

This administrative program is similar to the filesum program in Chapter 7 . It processes the output of the ls command.

The conditional expression "NR != 1" could have been put outside the main procedure as a pattern. While the logic is the same, using the expression as a pattern clarifies how the procedure is accessed, making the program easier to understand.

In that procedure, Morgan uses a series of conditionals that allow him to collect distribution statistics on the size of each user's mailbox.


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