You want to read a file into a Perl variable.

Following on from the Simple PHP demo of opening and reading contents of files, here is the Perl version.

Following script takes filename as a parameter, then opens it read-only and reads contents in data variable. Then it echoes a header and footer line, with the data in the middle.

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• Perl Docs - open
• Perl Docs - while

Showing the date last Sunday, using Perl.

Perl has some powerful functions, to perform date manipulation. Such as strftime, localtime and mktime.

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• Perl Docs - localtime
• Perl Docs - strftime
• Perl Docs - POSIX

Converting a string scalar into a number.

To convert a string scalar to a number, just add zero.

Sometimes Perl calculations get a bit screwed, when Perl decides it is dealing with a string - not a number.

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• Perl Docs - scalar

Converting a string into an array

To convert a string to an array, use split.

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• Perl Docs - split

Need to convert a string to a hash in Perl.

Split can also be used to generate a hash, from a string.

In this instance split looks at two things, the key to value separator (in this case an equals sign) and the comma to separate groups.

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• Perl Docs - split

You want to count the words in a file, using Perl.

Obviously wc -w can be used for this under UNIX.

But fairly decent demo on the power of split and push!

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• Perl Docs - push
• Perl Docs - split

You want to number each line of output.

Again other ways to do this with UNIX, such as grep -vn XXXX filename.

But sure there are times you want the line number, of standard input.

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• Perl Docs - print

You need help on a specific Perl function or module. Or just a general question.

Perl installation comes with its own documentation system.

In this post, I’ll just cover how to invoke the various perl documentation.

Going forward I’ll add posts describing how to create the different types of Perl doco.

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• Perl Docs - Intro

You have some way cool awk or sed scripts, but you want to use Perl.

Easy. Perl comes with some excellent binaries, which will convert AWK or SED scripts to Perl. Excellent tool for learning Perl too!!

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Sometimes you need to connect to mysql server with a UNIX socket, rather than a Port.

Generally this is when running multiple versions, on a box when you do not want to
or cannot connect to multiple ports.

If you want to connect to the mysql server from the command line, you can use -S.

Or within Perl - append mysql_socket to the dsn

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You want to view seconds since last change or use Perl to process a number of files.

Or maybe you just want a programmatic way to deal with file details, using something similar to the UNIX stat C routine.

Run stat against a file and display inode change time since epoch. See my other tip on converting to local time.

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• Perl Docs - stat
• Date handling in Perl - localtime

You want to check a specific number of arguments, have been supplied to your Perl script.

This snippet at the example tab, demonstrates how to check that 2 args, were postfixed to the Perl script.

If you only want to check one, then use ARGV!=0, for three 2, etc.

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• Perl Docs

You want to substitute a pattern in a number of files, making backups and modifying in place on the fly.

And you can do this in Perl - with a one liner!

An amazing bit of Perl and so quick!

This one liner will replace all occurrences of a pattern, with your replace and even create backups of files edited.

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• Perl Docs

You want to convert epoch into readable date and time.

Maybe you have a log file, which is pumping out lines prefixed with the epoch?

We use the perl function localtime to convert epoch into a date and time.

At the example tab is the code to convert that epoch, into a recognizable date and time.

localtime, can also return an array - take a look at the reference tag for more info.

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• Perl Docs - localtime

During my first encounters with Perl many years ago, I asked how can I get a specific column.

It was so easy in AWK!

Well here it is in Perl - see example tab.

BTW you can always write an awkscript and run it through a2p - very good for learning Perl!

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• Perl Docs
• Perl Docs - Awk to Perl

You want to capture the current epoch. Maybe to use in a log file, or as a filename.

Or maybe you want to calculate the date yesterday.

This piece of code is very useful for performing date calculations. You can obtain the current epoch (time in seconds since Jan 1 1970), then add 3600 for 1 hour - or 86400 for 24 hours hence.

Technorati Tags: Perl, epoch, date manipulation, Perl Coding School

• Perl Docs - predefined variables
• Perl Docs - localtime

You have a script which runs too long and you want to time it out, after a given number
of seconds.

Useful bit of code to time-out a section of your Perl script, via the alarm function.

See the example tab.

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• Perl Doc - alarm

You want to generate a SHA digest for a given string.

Perl has great encryption and digesting algorithms.

In the example tab we use the Digest Perl module.