I still can't get only the necessary lines from the file. (sashac88)

I still can't get only the necessary lines from the file.

sashac88

created: 2004-07-01 02:22:33

perlmonks

node
author

prlmnks

node
author

Good day,monks.
It's not the first time I ask about this..
The folloing is the example of files with commands.
Start context
duplex
Half
Pass level = 2
negotiation
Pass level = 2
back-pressure
Pass level = 2
* Exit context *
There are many different contexts in this file.But they all end with the line "* Exit context *". What I need is to be able to to parse the lines between the closest "START Context" and "* END context *" at the time.
If I use the following code:

open DATA,"c://xxx.txt";
while()
{
   if (/START context/ .. /* End Context */ )
   {
      print unless /(START context |* End context *)/;
   }
}

It prints all the lines (except what is in unless of course) between the first "Start context" and the last "* End context *". I tried to use non-greedy regular expression (.*?) ,but still didn't get the desired result. Can someone please help?
Thanks a lot in advance.

Edit by [castaway], added code tags

Re: I still can't get only the necessary lines from the file.

gaal

created: 2004-07-01 02:32:41

perlmonks

prlmnks

* is a metacharacter. Try escaping it in your regexps:

if (/START context/ .. /\* End Context \*/) {
    print unless /START context|\* End Context \*/;
}

Also, note that your data says "Exit" but your code looks for "End".

Re: I still can't get only the necessary lines from the file.

davido

created: 2004-07-01 02:35:47

perlmonks

prlmnks

One problem is your regexp. Here's what it is saying:

Match if:

Match "START context"
or
* is a quantifier, and can't be used as a bare character without escaping it. In the context of |*, I have no idea how it's going to be interpreted, but it won't be how you think.
Match "End context"
Match any amount of trailing space characters (because you used * again, which is a quantifier).

The "print unless..." statement should be as follows:

print unless ( /START context/ or /\* End context \*/ );

Another solution might be like this:

{
    local $/ = "* End Context *\n";
    while (  ) {
    s/^START context//;
    my @info = split /\n/;
    chomp @info;
    print "$_\n" foreach @info
}

Dave

Re: I still can't get only the necessary lines from the file.

Anonymous Monk

created: 2004-07-01 02:37:48

perlmonks

prlmnks

perl -e '/(START context |* End context *)/'
Quantifier follows nothing in regex; marked by <-- HERE in m/(START context |* <-- HERE  End context *)/ at -e line 1.

What do you think is wrong here? perldoc [perldoc://perlre]

Re: I still can't get only the necessary lines from the file.

ercparker

created: 2004-07-01 02:52:03

perlmonks

prlmnks

in your text file example you have Start context and * Exit context *
in your code you're matching for START context and End context
I modified the code to match correct, tested, and works fine:
will print everything except what your matching for in the print unless

open (DATA,") {
	if (/Start context/ .. /\* End Context \*/)  {
 		print unless /(Start context|\* Exit context \*)/;
 	}
}

Re^2: I still can't get only the necessary lines from the file.

sashac88

created: 2004-07-01 03:19:06

perlmonks

prlmnks

Oops -my mistake.I have the correct line in my code's unless. \* Exit context \*
The problem is that in print results I get lines that are not between the closest "Start context" and "* end context *".
I suspect that maybe the problem is in this line:
if (/Start context/ .. /\* End Context \*/)
which IMHO takes all the lines between the first "Start context" in the file and last "* end context *"
. Am I right? Or the line:
if (/Start context/ .. /\* End Context \*/)
looks for the closest "Start context" and "* End context *"
Thanks

Re^3: I still can't get only the necessary lines from the file.

gaal

created: 2004-07-01 06:00:50

perlmonks

prlmnks

The .. "flip-flop" operator (see perlop) is true "between" the two operands. That is, once the left-hand match is true, the flip-flop is true, until whenever the right-hand match succeeds. Then it's false until the left-hand match is true, and so on.

So, no: if (/Start context/ .. /\* End Context \*/) { doesn't "take" "all the lines between the first 'Start context' in the file and last '* end context *'", but indeed only those within any of the contexts (and the start marker too, but not the end marker).

Re: I still can't get only the necessary lines from the file.

sashac88

created: 2004-07-01 04:12:08

perlmonks

prlmnks

Sorry ,My mistake.I have the correct line in my code's unless. \* Exit context \* The problem is that in print results I get lines that are not between the closest "Start context" and "* end context *". I suspect that maybe the problem is in this line: if (/Start context/ .. /\* End Context \*/) which IMHO takes all the lines between the first "Start context" in the file and last "* end context *" . Am I right? Or the line: if (/Start context/ .. /\* End Context \*/) looks for the closest "Start context" and "* End context *" Thanks

Re: I still can't get only the necessary lines from the file.

muba

created: 2004-07-01 05:38:00

perlmonks

prlmnks

Would you please, please use <code> tags?

Re: I still can't get only the necessary lines from the file.

ercparker

created: 2004-07-01 11:02:54

perlmonks

prlmnks

I think I understand now
you want the text between the first Start and first Exit
you can throw in a last to exit the loop when matching Exit

open (DATA,") {
    if (/Start context/ .. /\* Exit context \*/)  {
         print unless /(Start context|\* Exit context \*)/;
         last if /\* Exit context \*/;
    }
}