Perl Reporting

© March 2008 Anthony Lawrence

I often forget about Perl's reporting formats, and I suspect that a lot of people do - we're so used to Perl as a programming language that we forget it's original namesake: Practical Extraction and Report Language. Reporting was a big part of Perl's beginnings, but it's hardly ever mentioned today.

In fact, it's been so long since I have used any of these features that I had to drag out my big Camel Book to review the whole subject - I had forgotten everything. Fortunately, it's not hard, and using these capabilities can make output much easier: you don't have to keep track of lines printed so that you can generate headers on new pages or print page numbers: Perl does that for you. You can justify and center, easily handle variable width data and more. Perl Report Formats make all this easy.

Here's an example using a format suggested in the Camel book (or online at Perl Formats)

:

#!/usr/bin/perl
# a report on the /etc/passwd file
format STDOUT_TOP =
                        Passwd File
Name                Login    Office   Uid   Gid Home
------------------------------------------------------------------
.

format STDOUT =
@<<<<<<<<<<<<<<<<<< @||||||| @<<<<<<@>>>> @>>>> @<<<<<<<<<<<<<<<<<
$name,              $login,  $office,$uid,$gid, $home
.

$= = 20;
# sets 20 lines per page
while (<>) {
( $name, $login,  $office,$uid,$gid, $home) =split /:/;
next if not $login;
write;

}

On my Mac, running that program with /etc/passwd as its argument produces this:

                        Passwd File
Name                Login    Office   Uid   Gid Home
------------------------------------------------------------------
nobody                 *     -2        -2 Unpri /var/empty
root                   *     0          0 Syste /var/root
daemon                 *     1          1 Syste /var/root
_uucp                  *     4          4 Unix  /var/spool/uucp
_lp                    *     26        26 Print /var/spool/cups
_postfix               *     27        27 Postf /var/spool/postfix
_mcxalr                *     54        54 MCX A /var/empty
_pcastagent            *     55        55 Podca /var/pcast/agent
_pcastserver           *     56        56 Podca /var/pcast/server
_serialnumberd         *     58        58 Seria /var/empty
_devdocs               *     59        59 Devel /var/empty
_sandbox               *     60        60 Seatb /var/empty
_mdnsresponder         *     65        65 mDNSR /var/empty
_ard                   *     67        67 Apple /var/empty
_www                   *     70        70 World /Library/WebServer
_eppc                  *     71        71 Apple /var/empty
_cvs                   *     72        72 CVS S /var/empty
_svn                   *     73        73 SVN S /var/empty
_mysql                 *     74        74 MySQL /var/empty
_sshd                  *     75        75 sshd  /var/empty
_qtss                  *     76        76 Quick /var/empty
_cyrus                 *     77         6 Cyrus /var/imap
_mailman               *     78        78 Mailm /var/empty
_appserver             *     79        79 Appli /var/empty
_clamav                *     82        82 ClamA /var/virusmails
_amavisd               *     83        83 AMaVi /var/virusmails
_jabber                *     84        84 Jabbe /var/empty
_xgridcontroller       *     85        85 Xgrid /var/xgrid/control
_xgridagent            *     86        86 Xgrid /var/xgrid/agent
_appowner              *     87        87 Appli /var/empty
_windowserver          *     88        88 Windo /var/empty
_spotlight             *     89        89 Spotl /var/empty
_tokend                *     91        91 Token /var/empty
_securityagent         *     92        92 Secur /var/empty
_calendar              *     93        93 Calen /var/empty
_teamsserver           *     94        94 Teams /var/teamsserver
_update_sharing        *     95        -2 Updat /var/empty

^L                      Passwd File
Name                Login    Office   Uid   Gid Home
------------------------------------------------------------------
_installer             *     96        -2 Insta /var/empty
_atsserver             *     97        97 ATS S /var/empty
_unknown               *     99        99 Unkno /var/empty
 

Ever had to handle variable length data in a report? That can be annoying, can't it? Let's say we have this text file:

02/04/2008:No changes
02/08/2008:Maintenance
02/16/2008:Major problems.  Disk crash, all work lost
02/17/2008:Starting over
02/19/2008:This is just too much work.  The project is not worth the trouble. I quit.
02/25/2008:Wow! Big raise.  Guess I don't quit.
 

Here's a little Perl script that eats that up:

#!/usr/bin/perl
format STDOUT =
Date              Action
@<<<<<<<<         ^<<<<<<<<<<<<<<<<<<<<
$date             $action
~                 ^<<<<<<<<<<<<<<<<<<<<
                  $action
~                 ^<<<<<<<<<<<<<<<<<...
                  $action
.

while (<>) {
($date,$action)=split /:/;
write;
}
 

If we run that against our data file, we'll get:

02/04/200         No changes
02/08/200         Maintenance
02/16/200         Major problems.  Disk
                  crash, all work lost
02/17/200         Starting over
02/19/200         This is just too much
                  work.  The project is
                  not worth the...
02/25/200         Wow! Big raise.
                  Guess I don't quit.
 

There's a lot more to this, I just wanted to give you a taste here. You can read the docs and play with it yourself but can probably easily see how much time and trouble this could save you.

Got something to add? Send me email.

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