Hi Perlers,
On 30 Sep 2004 10:11:29 +0100, Jose Alves de Castro
<[EMAIL PROTECTED]> wrote:
> On Wed, 2004-09-29 at 21:25, JupiterHost.Net wrote:
> > >>> I would like the output in the following format
> > >>> object1<...tab....>Description1
> > >>> object2<...tab....>Description2
> > >>> object3<...tab....>Description3
> > >>
> > >>
> > >> perl -lne 'BEGIN{$/="\n\n";}s/\n/\t/;print' FILENAME
> > >
> > >
> > >
> > > perl -l -00pe's/\n/\t/' FILENAME
> >
> > That's pretty slick you guys, he's sure to get an A+ ;)
> >
> > If your teacher requires the quotes to be removed:
>
> What if the teacher requires an explanation? O:-)
>
> It is my opinion that code should be explained, at least in this list.
> You're trying to teach people how to fish (and maybe swim). Giving them
> fish is good, of course, but tell them how you got it :-)
>
> That said, nice code :-)
>
> > perl -l -00pe's/\n/\t/;s/\"//g;' FILENAME
> >
> > :)
> --
> Jos� Alves de Castro <[EMAIL PROTECTED]>
> http://natura.di.uminho.pt/~jac
>
I'll give it a try.
First, it's good to know that the two Perl special variables '$/' and
'$\' are the input separator and output separator. By Default, they
will be $/ = \n (newline character) and $\ = undef (nothing. No
output separator).
Now, on the command line, the '-0' option will set the input separator
($/). In the above example, it's setting $/ = 0. Also, in the
example, the '-l' will do two things. First, it will automatically
chomp() whatever's in '$/', and then it will set the output separator
to be whatever the input separator will be. So, specific to our
example, first '-l' sets '$\' (output separator) to whatever '$/' is
(at this point, it's \n, or a newline). Then, the '-0' switch is
setting the $/ = 0 ( or null, or nothing!).
OK, next we have '-p' and '-e'. The '-e' tells Perl to read one line
(the one after the '-e') and use that as the code to process. The
'-p' causes Perl to assume the following code around your code:
LINE:
while( <> ) {
# your code goes here
} continue {
print or die "-p destination: $!\n";
}
So, this is going to process whatever files it finds on your command
line and then print '$_'!
Now, the code that's going into that block is, in our example:
s/\n/\t/;
s/\"//g;
So, we get this as the code Perl is running:
LINE:
while( <> ) {
s/\n/\t/; # Change newlines into tabs
s/\"//g; # Remove all double-quotes
} continue {
print or die "-p destination: $!\n";
}
but with the special $/ = 0 as the input separator and $\ = \n as the
output separator!
There! Am I right? This is fun ... we should do this more often!
This taught me a lot.
BTW, I found most of these explanations in the 'perldoc perlrun' and
'perldoc perlvar' pages. You can check out continue blocks with
'perldoc -f continue'.
--Errin
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