Linux System Administration Recipes A Problem-Solution Approach

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APPENDIX ■ PERL TIPSIt can also handle options with values, options with multiple names, and a widevariety of other possibilities. (It may also be overkill for a basic script, but it’suseful for more complicated ones.)• LWP::Simple: Grabs a web page with a single command.use LWP::Simple;my $document = get("http://www.itv.com/sport/tourdefrance/default.html")or die "Couldn't get TdF page";if ($document =~ /Armstrong/) { print "Highly unusual lack of Lance!");• There’s very little error handling (you get undef on failure and the content onsuccess), but it does what it does admirably straightforwardly.• Mail::Sendmail: Provides a simple module for sending mail from a script. It’ll usewhatever your default mail server is.use Mail::Sendmail;%mail = ( To => 'me@gmail.com',From => 'me@example.com',Message => "Talking to myself...");sendmail(%mail) or die $Mail::Sendmail::error;• Net::LDAP and Net::LDAPS: Provides various LDAP interface options. See recipe 2-10 for details.• Net::Ping: Provides a simple module that you can use to ping other hosts and getthe return time and other information.use Net::Ping;my $ping = Net::Ping->new();my ($ret, $duration, $ip) = $ping->ping($server, 5.5);• Perl::Tidy (aka perltidy): Tidies up badly formatted code (useful if you’re takingover someone else’s code and that person didn’t have your own high readabilitystandards) and will also output nicely formatted HTML with the -html option.> perltidy badscript.plBe warned! The more horrendous the input was, the higher the possibility thatperltidy will break it. Make sure that you test properly before and after to ensurethat the code is still doing the same thing.• Text::Table: Prints output in a nice table. You create the table and then load thedata in, and Text::Table handles the alignment and presentation. It’s basic butuseful.• Time::HiRes: Implements high-resolution (microsecond) timers. This is often usedby other modules, such as Net::Ping.use Net::Ping;use Time::HiRes;my $ping = Net::Ping->new();$ping->hires();250Download at WoweBook.Com
APPENDIX ■ PERL TIPSPerl Syntax NotesHere are a few brief notes about a couple of the corners of Perl syntax that I often find myself havingto refer to the documentation for. Remember, however, the Perl maxim: there’s more than one way todo it!open with |To get command output, you can use open with a pipe, as shown in recipe 4-2:open FILEHANDLE, '-|', 'command';while () {# do stuff!}This will pipe the output from command into FILEHANDLE, which the while() loop then iterates overline by line. If you use '|-' instead, the output from FILEHANDLE is piped to command.?:This syntax, which basically provides an if-then-else shorthand for assignments, can be useful.If the value before ? evaluates as true, then the value after ? is used for assignment; otherwise, the valueafter : is used. So this statement:my $a = $ok ? $b : $c;is a shorthand for this:my $a;if ($ok) {$a = $b;} else {$a = $c;}Use this with caution; it can be a neat way of doing things, but if you find yourself scatteringparentheses everywhere and/or having to look at it more than once to understand it, go back to thelonger version.251Download at WoweBook.Com
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Contents■About the Author .......
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■ CONTENTS3-7. Writing a Nagios P
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■ CONTENTS■Chapter 8: Using the
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■ CONTENTSAbout the Author■Juli
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■ CONTENTSAcknowledgmentsMany tha
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■ CONTENTSIntroductionThis book i
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■ INTRODUCTIONDownloading the Cod
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C H A P T E R 1■ ■ ■Saving Yo
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CHAPTER 1 ■ SAVING YOURSELF EFFOR
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C H A P T E R 2■ ■ ■Centraliz
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CHAPTER 2 ■ CENTRALIZING YOUR NET
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C H A P T E R 3■ ■ ■Monitorin
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CHAPTER 3 ■ MONITORING AND UPDATI
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C H A P T E R 4■ ■ ■Taking Ba
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CHAPTER 4 ■ TAKING BACKUPS AND MA
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C H A P T E R 5■ ■ ■Working w
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CHAPTER 5 ■ WORKING WITH FILESYST
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C H A P T E R 6■ ■ ■Securing
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CHAPTER 6 ■ SECURING YOUR SYSTEMS
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CHAPTER 7 ■ WORKING WITH APACHEOn
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CHAPTER 7 ■ WORKING WITH APACHEdi
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CHAPTER 7 ■ WORKING WITH APACHE4.
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CHAPTER 7 ■ WORKING WITH APACHE
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CHAPTER 7 ■ WORKING WITH APACHEAl
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CHAPTER 7 ■ WORKING WITH APACHE
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C H A P T E R 8■ ■ ■Making Be
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CHAPTER 8 ■ USING THE COMMAND LIN
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CHAPTER 9 ■ WORKING WITH TEXT IN
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Page 233 and 234: C H A P T E R 11■ ■ ■Tracking
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Page 251 and 252: C H A P T E R 12■ ■ ■Managing
Page 253 and 254: CHAPTER 12 ■ MANAGING TIME AND PE
Page 267 and 268: APPENDIX■ ■ ■Perl TipsSee rec
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Page 275 and 276: ■ INDEXenscript option (printing)
Page 277 and 278: ■ INDEX■NNagiosadding hosts to,
Page 279 and 280: ■ INDEXsyslogcentralized logging
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Linux System Administration Recipes A Problem-Solution Approach

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