Thanks Charles,
Once I knew what I was looking for I found it inthe books under "Backrefference" I
liked your
explaination better.
What if one want to implement certain code each time a match was found. And do
something like this.
while (<FILE>) {
if (/pid=$getty_pid/ && /dev=$ttydev/) {
foreach (/(.*?)='(.*?)'/g) {
$getty{$1}=$2
}
}
}
Is this legal?
Charles Galpin wrote:
> I guess I'll keep it on list since there seems to be some interest in
> regular expressions (and I'm left wondering why this is deemed such
> complicated code)
>
> If I'm not mistaken, the code really just needed to be (minus error
> handling) the following since all you cared about was the getty info. So
> we will look at this as an example, only because it doesn't match anything
> we don't care about (like the original because I wanted you to be able to
> use that info if I was wrong about my assumptions)
>
> open (FILE, "<file");
> while (<FILE>) {
> if ( /##### data dev=$ttydev, pid=$getty_id, caller='.*?',
>conn='(.*?)\/(.*?)\/(.*?)'/) {
> print "getty data: $1/$2/$3\n";
> last;
> }
> }
> close FILE;
>
> rpjday covered reading a file line by line and $_ so I won't repeat that.
>
> But what is this awfully compilcated looking stuff you say?
>
> if ( /##### data dev=$ttydev, pid=$getty_id, caller='.*?',
>conn='(.*?)\/(.*?)\/(.*?)'/) {
>
> We are using the matching operator // (man perlop), and applying it to $_
> which happens automatically so we don't need something like $line =~
> //. Each line is examined, and if the regular expression between the //
> matches, it returns true and we pass the if check.
>
> The regular expression is not that difficult. The $ttydev and $getty_id
> get expanded before the match, so it really looks like
>
> /##### data dev=ttyC12, pid=13032, caller='.*?', conn='(.*?)\/(.*?)\/(.*?)'/
>
> In this example. the only thing special about this is the .*? and the ()
>
> .*? .* matches zero or more characters. The ? just says don't be greedy
> (which perl is by default) and will stop matching at the first ' instead
> of all the way top the last tick of conn='' in the case of
> caller='.*?'. If I had used .*, I would have gotten one match on
> caller='.*?' and the value would have been everything from the ' to the
> last ' on that line.
>
> () these capture whats in between them and store them in variables named
> $1, $2 ... in the order they are found. You can even nest them.
>
> See man perlre for more info on these two
>
> print "getty data: $1/$2/$3\n";
>
> here I just use the matches
>
> last;
>
> This says once I find a match then fall out of the while loop - no sense
> looping through any more lines than you need to .
>
> }
>
> end of the if.
>
> Now what was so complicated and 'clever' about that?
>
> charles
>
> On Tue, 22 Feb 2000, Robert Canary wrote:
>
> > Hi Charles,
> >
> > Hey thanks for your and everyones help on such an offtopic subject. I have all of
>the
> > O'Reilly Perl books, but I something I never picked up on was the assignment of
>values
> > to the $1....7. I am still sure how this works, but had I understood it before it
> > would have made things allot esaier (and quicker perl code).
> >
> > One quick question: So anything that a pattern matches in a () is assigned to a
> > $1...$9, is this a correct statement? Since this post has now left the orginal
> > textus, could you drop me a quick yes or no off the mail-list, if you have a spare
> > moment.
> >
> > Thanks agin :-)
> >
> > Charles Galpin wrote:
> >
> > > Hi Robert
> > >
> > > Boy you have really made this hard on yourself (and us) :)
> > >
> > > Why didn't you post this line
> > >
> > > 02/18 15:54:26 ##### data dev=ttyC12, pid=13032,
> > > caller='none',conn='31200/LAPM/V42BIS', name='', cmd='/usr/sbin/pppd',
> > > user='/AutoPPP/'
> > >
> > > and say that you know the pid and the dev, and need to get the other
> > > fields when you match this line?
> > >
> > > My answer would (without all this fanfare) have been
> > >
> > > sub w1_connect_info {
> > > # This routine extract available info passed in the getty logs.
> > > # Here is a sample of the line we are looking for:
> > > # 02/18 15:54:26 ##### data dev=ttyC12, pid=13032, caller='none',
> > > conn='31200/LAPM/V42BIS', name='', cmd='/usr/sbin/pppd', user='/AutoPPP/'
> > > my ($getty_id,$ttydev) = @_;
> > > my ($line,$item);
> > > my (@getty_line);
> > >
> > > open (GETTYFILE, "</var/log/getty.log.$ttydev") || die "Can't open
> > > log.$ttydev: $!";
> > > while (<GETTYFILE>) {
> > > if ( /##### data dev=$ttydev, pid=$getty_id, caller='(.*?)',
> > > conn='(.*?)\/(.*?)\/(.*?)', name='(.*?)', cmd='(.*?)', user='(.*?)'/) {
> > > print "getty data: $2/$3/$4\n";
> > > print "other stuff you don't seem to care about: caller=$1
> > > name=$5 cmd=$6 user=$7\n";
> > > last;
> > > }
> > > }
> > >
> > > close GETTYFILE;
> > >
> > > } # sub w1_connect_info
> > >
> > > make sure you put a space before conn when you unwrap these lines.
> > >
> > > since the format is so well defined, you don't need to get fancy here
> > > charles
>
> --
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