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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