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Re: perl assignment question

#11

Feb 11th, 2009

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Originally Posted by KevinADC

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.

Oddly enough, the above posted (with the suggestions to try cd / and cd /windows and cd "/documents and settings") was tested in windows XP SP1. I went to start... run, and typed in cmd. Once the window was up, I typed cd /, and hit enter. While XP didn't completely flip out, it certainly did not take me to the root directory (\). Then, when I typed cd /windows/system32, this most certainly did error. Try it with a known branch, such as: cd /windows/system32. No can do. Notice the second entry of the command line... gives an error. The third (using \'s) does not. The rest of the lines... none of them work either (although, the cd / doesn't error, it also doesn't work.). This is not DOS. This is cmd.exe (not command.com). However, KevinADC is right that explorer.exe (windows Desktop shell) does allow the use of / in paths (such as typing a path in my computer's location bar). The question is... is that the file system, or is that explorer.exe?

According to O'Reilly & Associates (Section 2.2.2, point / bullet number 2, and the table in 2.2.4) Some Perl modules and functions allow the use of '/' as a path separator, but it is strongly discouraged as a use of good practice.

Last edited by Comatose; Feb 11th, 2009 at 7:22 am.

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Re: perl assignment question

#12

Feb 11th, 2009

I see that link I posted was broke, try again:

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

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Re: perl assignment question

#13

Feb 11th, 2009

That link does not want to post on this forum

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

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Re: perl assignment question

#14

Feb 11th, 2009

I trust O'Reilly significantly more than wikipedia. I also read on MSDN (will post when I get home) that it's the API calls and programs that do the translation, not NTFS Native.

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Re: perl assignment question

#15

Feb 11th, 2009

I have always had more success at the cmd line (for windows) with perl using "\\path\\file.txt" However, in a web environment (at least if you're running apache for windows) "/path/file.txt" works just fine.

That has been my experience anyway.

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

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Re: perl assignment question

#16

Feb 13th, 2009

Just to add a bit to the discussion. I was reading the perl FAQs to answer a question on a forumand came upon this:

Why can't I use "C:\temp\foo" in DOS paths? Why doesn't `C:\temp\foo.exe` work?

Whoops! You just put a tab and a formfeed into that filename! Remember that within double quoted strings ("like\this"), the backslash is an escape character. The full list of these is in "Quote and Quote-like Operators" in perlop. Unsurprisingly, you don't have a file called "c:(tab)emp(formfeed)oo" or "c:(tab)emp(formfeed)oo.exe" on your legacy DOS filesystem.

Either single-quote your strings, or (preferably) use forward slashes. Since all DOS and Windows versions since something like MS-DOS 2.0 or so have treated / and \ the same in a path, you might as well use the one that doesn't clash with Perl--or the POSIX shell, ANSI C and C++, awk, Tcl, Java, or Python, just to mention a few. POSIX paths are more portable, too.

Last edited by KevinADC; Feb 13th, 2009 at 1:05 pm. Reason: disable smilies

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Re: perl assignment question

#17

Feb 17th, 2009

I think I changed it to what some of the posts are saying but its still not working. This is what Ive got.

 Help with Code Tags 
 Perl Syntax (Toggle Plain Text) 
#!/usr/bin/perl -w
# Assignment3Ex1.pl
 
use strict;
 
open(INFH, '<', "C:\Documents and Settings\Home\Desktop\perl\gettysburg.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, '<', "C:\Documents and Settings\Home\Desktop\perl\gettysburg.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;

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Re: perl assignment question

#18

Feb 17th, 2009

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Originally Posted by Comatose

I trust O'Reilly significantly more than wikipedia. I also read on MSDN (will post when I get home) that it's the API calls and programs that do the translation, not NTFS Native.

Its windows itself. Support for forward and backslashes in builtin to Windows. You can google around and find MicroSoft articles that explain it if interested. I think thats enough on the subject.

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Re: perl assignment question

#19

Feb 17th, 2009

If it were windows itself, don't you think cmd.exe (which is a windows program) would support it? I would imagine so. According to MSDN (I was holding off on it, but will post it when I get home) they say it's the API functions that translate the / slashes to \ slashes. That would mean it's not windows itself (ie: the file system) but the programs that are running on it (ie: explorer.exe, and so forth). Just for fun, try this:
start, run, type in: /
Oops.
Start, run, type in: \
interesting.

http://www.cygwin.com/cygwin-ug-net/...fectively.html <<-- Under Pathnames
And straight from the horse's mouth:
http://msdn.microsoft.com/en-us/libr...22(VS.80).aspx

Last edited by Comatose; Feb 17th, 2009 at 3:58 pm.

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Re: perl assignment question

#20

Feb 17th, 2009

I guess when we say Windows we should be more specific. Windows operating systems based on NT are different than older operating systems. The older ones support both slashes at the kernel level where NT does not. NT based systems do a conversion before the kernel level (in the APIs apparently). I had a link that explained all this on the MS website but the link now returns a "not found" page.