Perl

Perl RSS

perl assignment question

Please support our Perl advertiser: Programming Forums - DaniWeb Sister Site

•

Join Date: Dec 2008

Posts: 11

Reputation: mtramnes is an unknown quantity at this point

Solved Threads: 0

mtramnes

Offline

Newbie Poster

perl assignment question

Feb 10th, 2009

I have a perl assignment I have a question about. I have to take a text file (gettysburgh.txt) and I have to alter it. I think my code is correct but when I run the program it says no such file exists. The file is saved on my computer so I was hoping someone could tell me what I was doing wrong.

 Help with Code Tags 
 Perl Syntax (Toggle Plain Text) 
#!/usr/bin/perl -w
# Assignment3Ex1.pl
 
use strict;
 
open(INFH, '<', 'gettysburgh.txt') or die $!;
open(OUTFH, '>', 'ex1out.txt') or die $!;
 
while (<INFH>) {
next if /^\s*$/;
	my @words = split;
	print OUTFH "$_\n" foreach @words;
}
 
close INFH;
close OUTFH;
#!/usr/bin/perl -w
# Assignment3Ex1.pl

use strict;

open(INFH, '<', 'gettysburgh.txt') or die $!;
open(OUTFH, '>', 'ex1out.txt') or die $!;

while (<INFH>) {
next if /^\s*$/;
	my @words = split;
	print OUTFH "$_\n" foreach @words;
}

close INFH;
close OUTFH;

•

Join Date: Mar 2006

Posts: 898

Reputation: KevinADC has a spectacular aura about

Solved Threads: 67

KevinADC

Offline

Practically a Posting Shark

Re: perl assignment question

Feb 10th, 2009

try using the full path to the file:

open(INFH, '<', 'full/path/to/gettysburgh.txt') or die $!;

•

Join Date: Feb 2009

Posts: 57

Reputation: mitchems is an unknown quantity at this point

Solved Threads: 2

mitchems

Offline

Junior Poster in Training

Re: perl assignment question

Feb 10th, 2009

•

Originally Posted by KevinADC

try using the full path to the file:

open(INFH, '<', 'full/path/to/gettysburgh.txt') or die $!;

I find this open statement interesting... I always do something like this:

Help with Code Tags

(Toggle Plain Text)

open(INFH,"<\\full\\path\\to\\gettysburgh.txt") #on windows
open(INFH,"</full/path/to/gettysburgh.txt") #on unix

What I don't understand is the ,'<', construct... that's not something I usually do.

And don't tell me there isn't one bit of difference between null and space, because that's exactly how much difference there is.

Larry Wall

•

Join Date: Mar 2006

Posts: 898

Reputation: KevinADC has a spectacular aura about

Solved Threads: 67

KevinADC

Offline

Practically a Posting Shark

Re: perl assignment question

Feb 10th, 2009

Window fully supports forward slashes in directory paths. It always has. You can start using them from now on.

This is the three argument style of open:

open(INFH, '<', 'full/path/to/gettysburgh.txt') or die $!;

Its safer to use than the two argument style:

I'm pretty sure its convered in the open() functions documentation:

http://perldoc.perl.org/functions/open.html

•

Join Date: Feb 2009

Posts: 57

Reputation: mitchems is an unknown quantity at this point

Solved Threads: 2

mitchems

Offline

Junior Poster in Training

Re: perl assignment question

Feb 10th, 2009

Yeah I use the forward slash "/" in windows as well and windows/perl supports it. One thing I HAVE found is that Apache for windows is the only app I have come across that supports directory (or folder-level) permissions. What I found was that if folders are set as read-only, the only way to take that attribute off and have apache (or mod-perl or cgi perl) control a particular directory is to go to the cmd line and use attrib to remove the read only traits at the folder level. That is the only windows-weirdness I have found (and I found it with Apache 2 only).

As for the 3 argument open statement, I have never seen it before, but, perhaps, if that is the way they teach it, I should start using it - haha.

Mike

•

Originally Posted by KevinADC

Window fully supports forward slashes in directory paths. It always has. You can start using them from now on.

This is the three argument style of open:

open(INFH, '<', 'full/path/to/gettysburgh.txt') or die $!;

Its safer to use than the two argument style:

I'm pretty sure its convered in the open() functions documentation:

http://perldoc.perl.org/functions/open.html

And don't tell me there isn't one bit of difference between null and space, because that's exactly how much difference there is.

Larry Wall

•

Join Date: Dec 2004

Posts: 2,413

Reputation: Comatose is a jewel in the rough

Solved Threads: 211

Comatose

Offline

Taboo Programmer

Re: perl assignment question

Feb 10th, 2009

I'm pretty sure windows does not support paths with / as the separator. Try this: cd / or cd /windowsand then try this cd \windows. What I'm guessing happens here, is Perl (and other languages that do this, such as python) are smart enough to know that even though we hacker-esque folks use / in a path, that we really mean \, and naturally adjusts it

•

Join Date: Feb 2009

Posts: 57

Reputation: mitchems is an unknown quantity at this point

Solved Threads: 2

mitchems

Offline

Junior Poster in Training

Re: perl assignment question

Feb 10th, 2009

Comatose,

You are correct at the shell level. - windows does NOT do that. I use the double backslashes in a file path because I usually set a data or file path (like $DATAROOT="\\a\\b\\c") and then substitute stuff in double quotes, rather than single - in which the double back quotes on windows work far better (i.e. "$DATAROOT\\$morepath\\$filespec"). Perl, python, ruby, java, etc. are smart enough to translate. Also, cygwin, which I always install on my windows systems (and which can use bash - which I love - btw I am I unix guy suffering through windows) can also do that translation. But ultimately, you are correct, the regular windows shell does NOT do that translation, only the apps - i.e. perl, python, ruby, cygwin do that.

Mike

•

Originally Posted by Comatose

I'm pretty sure windows does not support paths with / as the separator. Try this: cd / or cd /windowsand then try this cd \windows. What I'm guessing happens here, is Perl (and other languages that do this, such as python) are smart enough to know that even though we hacker-esque folks use / in a path, that we really mean \, and naturally adjusts it

And don't tell me there isn't one bit of difference between null and space, because that's exactly how much difference there is.

Larry Wall

•

Join Date: Mar 2006

Posts: 898

Reputation: KevinADC has a spectacular aura about

Solved Threads: 67

KevinADC

Offline

Practically a Posting Shark

Re: perl assignment question

Feb 11th, 2009

•

Originally Posted by Comatose

I'm pretty sure windows does not support paths with / as the separator. Try this: cd / or cd /windowsand then try this cd \windows. What I'm guessing happens here, is Perl (and other languages that do this, such as python) are smart enough to know that even though we hacker-esque folks use / in a path, that we really mean \, and naturally adjusts it

Thats DOS (or other shell), not Windows. DOS uses forward slashes as switches, so you can't use them in directory paths. But Windows does fully support them. Its Windows itself that translates forward slashes into backslashes. Try using backslashes in Unix directry paths with perl or python and see what happens.

Last edited by KevinADC; Feb 11th, 2009 at 3:03 am.

•

Join Date: Mar 2006

Posts: 898

Reputation: KevinADC has a spectacular aura about

Solved Threads: 67

KevinADC

Offline

Practically a Posting Shark

Re: perl assignment question

Feb 11th, 2009

You can see here listed under directory paths for Windows:

http://en.wikipedia.org/wiki/Path_(computing)

In fact they list DOS as also accepting both \ / in directory paths. Maybe there is a way in DOS to change the path seperator. But when I try it it does not work in DOS, but it does in Windows.

Last edited by KevinADC; Feb 11th, 2009 at 2:59 am.

•

Join Date: Feb 2009

Posts: 57

Reputation: mitchems is an unknown quantity at this point

Solved Threads: 2

mitchems

Offline

Junior Poster in Training

Re: perl assignment question

#10

Feb 11th, 2009

Interesting. Like I said, I have cygwin installed and it gives me the unix commands (ls, grep, pwd, etc.) and it gives me bash in dos/windows. I always thought that that was why I got / to work. I put cyg-win before windows commands in my system so when I "cd" i am using the unix-ish version, not dos or windows.

•

Originally Posted by KevinADC

You can see here listed under directory paths for Windows:

http://en.wikipedia.org/wiki/Path_(computing)

In fact they list DOS as also accepting both \ / in directory paths. Maybe there is a way in DOS to change the path seperator. But when I try it it does not work in DOS, but it does in Windows.

And don't tell me there isn't one bit of difference between null and space, because that's exactly how much difference there is.

Larry Wall