Perl Problem

jmc1987 · 11-05-2011, 12:29 PM

I copied a perl program and execute it out of the book and I get nothing. I doubled checked and trippled check made sure everything was type correctly and the program doesn't execute how the book said it should.

Code:

#!/usr/bin/perl -w  
 
print "Your weight:";  
$_=<STDIN>;  
chomp;  
s/^\s+//;   # Remove leading spaces, if any.  
if (m/(lbs?|kgs?|kilograms?|pounds?)/i) {  
        if (s/\s*(kgs?|kilograms?).*//) {  
               $_*=2.2;  
        } else {  
               s/\s*(lbs?|pounds?).*//;  
        }  
}  
print "Your weight on the moon: ", $_*.16667, " lbs\n";

it suppose to print something like

Quote:

./moon.pl
Your weight: 150: lbs
Your weight on the moon: 25.00005lbs

or

./moon.pl
Your weight: 90kg
Your weight on the moon: 90.9090 lbs

And if your wondering the lesson example is from a lesson on expression, pattern finding and manipulation from book "Sams Teach Yourself Perl in 24 Hours".

The book is based on perl 5.6 and I use v5.10.1 so maybe it was a updated that changed how the code worked?

Sergei Steshenko · 11-05-2011, 12:33 PM

Quote:

Originally Posted by jmc1987

I copied a perl program and execute it out of the book and I get nothing. I doubled checked and trippled check made sure everything was type correctly and the program doesn't execute how the book said it should.

Code:

#!/usr/bin/perl -w  
 
print "Your weight:";  
$_=<STDIN>;  
chomp;  
s/^\s+//;   # Remove leading spaces, if any.  
if (m/(lbs?|kgs?|kilograms?|pounds?)/i) {  
        if (s/\s*(kgs?|kilograms?).*//) {  
               $_*=2.2;  
        } else {  
               s/\s*(lbs?|pounds?).*//;  
        }  
}  
print "Your weight on the moon: ", $_*.16667, " lbs\n";

The book is based on perl 5.6 and I use v5.10.1 so maybe it was a updated that changed how the code worked?

What is "nothing" ? E.g. is any message printed ?

Anyway, start from here: http://perldoc.perl.org/ - I've seen too many wrong examples in this forum copied from all kinds of strange sites/books.

Cedrik · 11-05-2011, 12:47 PM

The script should work, at least it does on my system (slackware 13.37, perl v.5.12.3)

jmc1987 · 11-05-2011, 12:53 PM

Quote:

Originally Posted by Cedrik

The script should work, at least it does on my system (slackware 13.37, perl v.5.12.3)

Are you able to interact with it by typing in a weight and getting output. when I run it just does nothing.

Cedrik · 11-05-2011, 01:32 PM

Yes, I type weight values and get output...

jmc1987 · 11-05-2011, 01:34 PM

Okay weird story I'm editing with gedit and the output would be

Quote:

@james@xion:~/Documents/Perl$./moon.pl
@james@xion:~/Documents/Perl$

I recreated the file using cli editor nano and it got the output I should

Quote:

james@xion:~/Documents/Perl$ ./moon.pl
Your weight:100 lbs
Your weight on the moon: 16.667 lbs
james@xion:~/Documents/Perl$ ./moon.pl
Your weight: 90 kg
Your weight on the moon: 33.00066 lbs
james@xion:~/Documents/Perl$

So why it wouldn't work the first go around who knows?

Sergei Steshenko · 11-05-2011, 01:36 PM

Quote:

Originally Posted by jmc1987

Okay weird story I'm editing with gedit and the output would be

I recreated the file using cli editor nano and it got the output I should

So why it wouldn't work the first go around who knows?

Create it again with 'gedit', save it with a different name, make sure it doesn't work, 'diff' the two files.

jmc1987 · 11-05-2011, 02:02 PM

Okay I uploaded to files moon.pl.txt works for me and moont.pl.txt doesn't do nothing and shows no errors.

They both look the same to me

Sergei Steshenko · 11-05-2011, 02:43 PM

Quote:

Originally Posted by jmc1987

Okay I uploaded to files moon.pl.txt works for me and moont.pl.txt doesn't do nothing and shows no errors.

They both look the same to me

No, they are different:

Code:

sergei@amdam2:~> diff moon.pl.txt moont.pl.txt
1,14c1
< #!/usr/bin/perl -w
<
< print "Your weight:";
< $_=<STDIN>;
< chomp;
< s/^\s+//;   # Remove leading spaces, if any.
< if (m/(lbs?|kgs?|kilograms?|pounds?)/i) {
<         if (s/\s*(kgs?|kilograms?).*//) {
<                $_*=2.2;
<         } else {
<                s/\s*(lbs?|pounds?).*//;
<         }
< }
< print "Your weight on the moon: ", $_*.16667, " lbs\n";
---
print "Your weight on the moon: ", $_*.16667, " lbs\n";
\ No newline at end of file
sergei@amdam2:~>

- it may be one of them has DOS line endings:

Code:

sergei@amdam2:~> file moon.pl.txt
moon.pl.txt: a /usr/bin/perl -w script text
sergei@amdam2:~> file moont.pl.txt
moont.pl.txt: a /usr/bin/perl -w\015\015print "Your w script text
sergei@amdam2:~>

.

Read 'man hexdump' and start further investigation.