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perl print question

Posted on 2006-11-29
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Last Modified: 2008-01-16
I have this command that give me what I need but can't get the print out right.

perl -ne 'if (/(\[.*\])/ & /calid=(.*?).dtstart=(.*?)&.*dtend=(.*?)&(summary=.*)&desc=/ && !/uid=/) {print "$1\t$2\t$3\t$4\t$5\n"}' log.txt


problem here is always prints the $1 $2.... starting with the second set of  /..../   what do I need to do if I want to print  from both  

example: print $1 and $2 from this pattern
      '/.....(....)/  &  /...(...)/'


Thanks,

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Question by:bt707
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Author Comment

by:bt707
ID: 18038063

I got it to work by doing this.

perl -ne 'if (/(\[.*0000\]).*?calid=(.*?).dtstart=(.*?)&.*dtend=(.*?)&(summary=.*)&desc=/ && !/uid=/) {print "$1\t$2\t$5\t$3\t$4\n"}'  log.txt

but is there a better way to do what I was trying to do above.


Thanks,
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Expert Comment

by:ozo
ID: 18040333
what would you consider to be better?
The main differerence between what you were saying you were trying to do and what you did is that what you did is that what dyou did won't match if the (\[.*0000\]) doed not come before the calid, and you print in a different order
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Author Comment

by:bt707
ID: 18041227
I got that part sorted out, I had just posted this as a example but had a few things out of line here.

I figure the part out I needed for the search but what I was now trying to do was to see how you could print out the
$1 and $2 if you had them in a search such as  '/.....(....)/  &  /...(...)/'  everytime I try this it always ignores one of them

works fine if I have all the $n between /......./   but when I have a command with a  /...../ &  /....../ in it I can't get it to work.
so trying to figure out how you would print out $1 and $2 in a command such as this

perl -ne 'print  "$1\t$2\n" if /someword(.*?)someword/  & /someword(.*?)someword/' file.txt


Hope that shows what I'm trying to figure out.


Thanks,

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Assisted Solution

by:mjcoyne
mjcoyne earned 200 total points
ID: 18041336
The problem is that it's two regular expressions.  If you try:

perl -ne 'print  "$1\t$2\n" if /firstword(.*?)firstword/  & /secondword(.*?)secondword/' file.txt

and they both match, then $1 holds the "firstword" match for a very short time, because the contents of $1 is immediately replaced by the "secondword" match.

You need to reassign the contents of $1 from the first match to another variable before proceeding to the second match, or it is lost...
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Accepted Solution

by:
jmcg earned 300 total points
ID: 18041376
The assignments to $1, $2, etc are temporary, that is, they will be overwritten the very next time you have a pattern match with subgroups. You must capture the values of the subgroups before the second match is attempted. Trying to do this in a perl one-liner will probably become unwieldy.

One way to capture the subgroup matches is an array assignment:

instead of your example
    /.....(....)/  &  /...(...)/

you could do something like
    ($m1) = /.....(....)/ and ($m2) = /...(...)/;

followed by

    print "$m1\t$m2\n";
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Author Comment

by:bt707
ID: 18041422
ok, Thanks to everyone for the explaination, now I see what the problem is and why it's doing what it is and thanks to jmcq for the good example of how to work this out.


Thanks again!!
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