Calling pax within a perl script (was stupid substitution question)

viffer has asked for the wisdom of the Perl Monks concerning the following question:

Thanks for everyones comments on the issue I was having simply replacing a '.' with '\.'. I've now realized that wasn't the issue. The code I had was working, it was looking at in in perl debug mode that was giving me a strange result.
I receive a tarred file that has the directory path within it. What I'm trying to do is untar the file into a different directory using pax. I thought the problem was due to the substitution not recognizing full stops within the directory name. However I have now found that whilst the command
pax -r -f pax.tar -s'/\/home\/kev\/pax\// \/data\/kev\/atlanta\/emtex\/invoices\//p'
works on the command line with the following result

$ tar -tvf pax.tar
drwxrwxr-x 252 1        0 Aug 11 14:12:55 2010 /home/kev/pax/
-rw-rw-r-- 252 1        0 Aug 11 14:12:52 2010 /home/kev/pax/t1
-rw-rw-r-- 252 1        0 Aug 11 14:12:54 2010 /home/kev/pax/t2
-rw-rw-r-- 252 1        0 Aug 11 14:12:55 2010 /home/kev/pax/t3

$ pax -r -f pax.tar -s'/\/home\/kev\/pax\// \/data\/kev\/atlanta\/emte
+x\/invoices/p'
/home/kev/pax/t1 >>  /data/kev/atlanta/emtex/invoices/t1
/home/kev/pax/t2 >>  /data/kev/atlanta/emtex/invoices/t2
/home/kev/pax/t3 >>  /data/kev/atlanta/emtex/invoices/t3
[download]

when I try to embed the command into a perl script via

my $homedir="/home/kev";
chdir $homedir;
my $cmd = "pax -r -f pax.tar -s'/\/home\/kev\/pax\// \/data\/kev\/atla
+nta\/emtex\/invoices\//p'";
system ( $cmd );
[download]

I get the error
pax: 0511-660 A replacement string was not added : 0511-661 An invalid trailing option was specified with the -s option
So what I *should* have been asking was, what am I doing wrong when I embed this pax command into my perl script?
Thanks guys and gals
Kev

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Re: Calling pax within a perl script (was stupid substitution question) by JavaFan (Canon) on Aug 11, 2010 at 09:40 UTC
That's because your backslashes get "eaten" by the double quotes in perl. Use `q{}` instead of the double quotes. Note also that `pax` allows any delimiter instead of `/`. Choosing a different one means you don't need backslashes at all.	[reply] [d/l] [select]
Re^2: Calling pax within a perl script (was stupid substitution question) by viffer (Beadle) on Aug 11, 2010 at 11:56 UTC
Thank you - appreciate your help. Whilst this works perfectly for `my $cmd = q{pax -r -f /home/kev/pax.tar -s'/\/home\/kev\/pax\//\/data\/kev\/atlanta\/emtex\/invoices\//p'};` When the directory name has several nodes and the filename being paxed/untarred is a variable I guess it isn't interpolating correctly `$command= q{pax -r -f $file -s'/DirPart1.DirPart2.DirPart3/SubDir\//\/data\/kev\/atlanta\/emtex\/invoices\//p'};` I have tried several variants of this, such as `$command= q{pax -r -f $file -s'/DirPart1\.DirPart2\.DirPart3\/SubDir\//\/data\/kev\/atlanta\/emtex\/invoices\//p'};` When running this I get the error: A file or directory in the path name does not exist. which makes me think the string isn't being interpolated correctly. I can see how using a different delimiter would obviate the need for using backslashes in the first example that works, but in the second example don't I need escape backslashes for the '.' if not for the subdir '/'?	[reply] [d/l] [select]
Re^3: Calling pax within a perl script (was stupid substitution question) by JavaFan (Canon) on Aug 11, 2010 at 12:14 UTC
$file won't interpolate inside q{}. A handful of alternatives: `$command = "pax -r -f $file -s'!DirPart1.DirPart2.DirPart3/SubDir/!/data/kev/atlanta/emtex/invoices/!p'"` `$command = qq{pax -r -f $file } . q{-s'/DirPart1.DirPart2.DirPart3\/SubDir\//\/data\/kev\/atlanta\/emtex\/invoices\//p'};` `$command = sprintf q{pax -r -f %s -s'/DirPart1.DirPart2.DirPart3/SubDir\//\/data\/kev\/atlanta\/emtex\/invoices\//p'}, $file;` `$command= q{pax -r -f $file -s'/DirPart1.DirPart2.DirPart3/SubDir\//\/data\/kev\/atlanta\/emtex\/invoices\//p'}; $command =~ s/\$file/$file/;` Or something else.	[reply] [d/l] [select]
Re^4: Calling pax within a perl script (was stupid substitution question) by viffer (Beadle) on Aug 12, 2010 at 03:41 UTC
Re: Calling pax within a perl script (was stupid substitution question) by Utilitarian (Vicar) on Aug 11, 2010 at 09:42 UTC
Try printing $cmd to see what it contains. `print "Good ",qw(night morning afternoon evening)[(localtime)[2]/6]," fellow monks."`	[reply] [d/l]