Perl Reporting

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.

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