The PERL Programming Language
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PERL (Practical Extraction and Report Language) is a
relatively new language. It was created in 1986 by Larry Wall. It has gone
through a versions Perl, Perl4, and, the newly released Perl5.
Perl5 adds the following features: Regular expression
enhancements, Arbitrarily nested data structures, Modularity and reusability,
Object-oriented programming, Many usability enhancements, Simplified grammar,
Lexical scoping, POSIX compliant, Package constructors and destructors,
Multiple simultaneous DBM implementations, and Subroutine definitions may
now be autoloaded.
Perl's strength lies in it's ability to interact with
it's environment. It is a very powerful string manipulation language. It
is able to open and manipulate many files from within the same program,
with ease. It can manipulate UNIX shells, and issue commands to the system.
All of these features make it a powerful Administrative tool that is in
use on just about all major UNIX systems. It's popularity can be seen in
the conversion of Perl to many home PC systems. It has been translated
to function in MS-DOS, Windows, Windows 95, Macintosh DOS, and Amiga DOS,
just to name a few.
New Directions for Perl5
Perl is starting to move towards it's C heritage by
adding the ability to program using objects. It also is added the ability
to be as structured, or unstructured, as you want it to be.
used in preparing this summary are: Programming perl, written by Larry
Wall and Randal Schwartz. It is an excellent source of information, and
does a very good job of teaching you the intricacies of the language. The
book is published by O'Reilly & Associates, a very good source for
computer books. To visit their web page, just click here.
And, finally, you can visit the Perl
Archive, on the World Wide Web. It contains a lot of information that
may be helpful to you in your quest to learn perl.
Here are some sample perl programs.
The first is a simple hello world program. When run,
it will simply print out "Hello World!" onto the screen. Click here to
see the source code, or click here to
download the code.
The second code is a little more complicated, and
shows off perl's string handling power. It takes a file, specified by the
user, either by being prompted by the program, or indicated on the command
line, and removes all the spaces from it. The modified lines are written
to a file with a .stp extention.
Example: The command line statement,
strip.pl file.txt, is the exact same
thing as this prompt from the program, Please enter the name of
the file to strip of spaces: file.txt. The program
output would then be written to the file,
This is just a sample of perl's sting manipulation
power. You can specify just about anything for the program to search and
replace. A good use of this is creating HTML documents from text files.
You can specify key words for the program to zero in on, and replace those
words a hyper text code. Click here to see the source
code, or click here to download
Here is another example of perl's string
manipulation power hower, this time we combine string manipulation with
some file handling capabilities. This program demonstrates prompting the
user for input, searching, and file manipulation. It prompts the
user for an input filename, an output filename, a search filename and a
replacement string, and replaces all occurences of the search pattern with
the replacement string while copying the input file to the output file.
Click here to see the source code, or click
here to download the code.
This is a more advanced example that demonstrates
user input, string manipulation, basic control statements, file manipulation,
and the mail command. The program asks for a the user to enter their name.
If the user's name is Randal then the user is greeted otherwise, the user
is asked to enter a secret word which must correspond to an entry in a
pre-exising password file. If the user fails to enter the correct
password the the program sends mail to the programs's author notifying
him of the users's failed attempt to login. Click here to see the
source code, or click here to download
Learning Pearl, 2nd Edition O'Reilly & Associates, Inc, 1997 CA.
Last modified: 1:00 AM on 12/8/1997
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