| |||||||||||
| |||||||||||
About dieing in Perl
An Introduction to Standards in Perl example from a Well House Consultants training course
More on An Introduction to Standards in Perl [link]
Source code: chink Module: P711
=head1 If you want to end a program in Perl, you can get out quickly enough with an exit function call. But that's probably just a part of what you'll be wanting to do - you'll be wanting to generate an error message on the error channel (STDERR) too, and perhaps to tell your user rather more about why the program died. The die function provides a message on STDERR and the exits your program. If you add a \n on as the last character, it will NOT tell you the line number in your code where it died, but with the \n it does tell you. Note that if you have your die function tell you the line number, it will also tell you how many lines have been read from the latest file. At first, this will seem odd but it's very useful indeed in helping to identify which line of a long data file caused your program to halt! Some useful variables to use within die strings: $0 - program name $. - number of lines of data read in $! - error message from open function =cut @ARGV < 2 and die ("Usage: $0 perlregex filename\n"); ($lookfor, $file) = @ARGV; open (FH,$file) or die ("$0: Input file $file problem\n$!"); while (<FH>) { if (/$lookfor/) {die("Data trap");} } print "Completed Correctly\n"; __END__ Sample output: Dorothy:p82 grahamellis$ perl chink Usage: chink perlregex filename Dorothy:p82 grahamellis$ perl chink Java ../requst.xyz chink: Input file ../requst.xyz problem No such file or directory at chink line 33. Dorothy:p82 grahamellis$ perl chink Java ../requests.xyz Data trap at chink line 35, <FH> line 2. Dorothy:p82 grahamellis$ perl chink Javascript ../requests.xyz Completed Correctly Dorothy:p82 grahamellis$ Learn about this subject
This module and example are covered on our public Perl Extra course. If you have a group of
three or more trainees who need to learn the subject, we can also arrange a
private or on site course for you.
Books covering this topic
Yes. We have over 700 books in our library. Books
covering Perl are listed here and when you've selected a
relevant book we'll link you on to Amazon to order.
Other Examples
This example comes from our "An Introduction to Standards in Perl" training module. You'll find a description of the topic and some
other closely related examples on the "An Introduction to Standards in Perl" module index page.
Full description of the source code
You can learn more about this example on the training courses listed on this page,
on which you'll be given a full set of training notes.
Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License. Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre. • The Horse's mouth provides a daily tip or thought. • Further resources are available via the resources centre. • All of these resources can be searched through through our search engine • And there's a global index here. Web site author
Purpose of this website
This is a sample program, class demonstration or answer from a
training course. It's main purpose
is to provide an after-course service to customers who have attended our
public private or
on site courses, but the examples are made
generally available under conditions described below.
Conditions of use
Past attendees on our training courses are welcome to use individual
examples in the course of their programming, but must check
the examples they use to ensure that they are suitable for their
job. Remember that some of our examples show you how not to do
things - check in your notes. Well House Consultants take no responsibility
for the suitability of these example programs to customer's needs.
This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details. Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request. |
| ||||||||||
PH: 01144 1225 708225 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho PAGE: http://www.wellho.net/resources/ex.php • PAGE BUILT: Sun Oct 11 14:50:09 2020 • BUILD SYSTEM: JelliaJamb |