Re^2: Extract a pattern from a string

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Re^3: Extract a pattern from a string by NetWallah (Canon) on Jun 10, 2012 at 14:46 UTC
This version is slightly more efficent: `perl -E 'my $s="ME170-5/2/8-ME172-2/2/6-ME4028"; while ($s=~m\|(\d{1,2 +}/\d{1,2}/\d{1,2})\|g){++$x;say "$x Found $1:" . " POS=" . (pos($s)-l +ength($1)+1)}'` [download] The reason is that the 'index' operator re-scans the string, while 'pos' uses an existing value, and the 'length' computation is significantly faster than scanning. Update: It also does not suffer from the bug ambrus (++) points out below. I hope life isn't a big joke, because I don't get it. -SNL	[reply] [d/l]
Re^4: Extract a pattern from a string by avim1968 (Acolyte) on Jun 11, 2012 at 05:35 UTC
Hi I have made those two codes based on what you wrote. in the case of multiple identical port numbers in the string. i need to know which would be faster/wiser to use ? `$s=ME170-5/2/8-ME172-5/2/8-ME4028ME172-5/2/8-ME196-5/2/8-ME4002; while ($s=~m/(\d{1,2}\/\d{1,2}\/\d{1,2})/g) {++$r;print "$r Found $1:" + .(pos($s)-length($1)+1) .$nl;}<br>` [download] _OUTPUT_ 1 Found 5/2/8:7 2 Found 5/2/8:19 3 Found 5/2/8:37 4 Found 5/2/8:49 `$s=ME170-5/2/8-ME172-5/2/8-ME4028ME172-5/2/8-ME196-5/2/8-ME4002; while ($s=~m/(\d{1,2}\/\d{1,2}\/\d{1,2})/g) {++$e;print "$e Found $1:" + .($-[1]+1) .$nl;}<br>` [download] _OUTPUT_ 1 Found 5/2/8:7 2 Found 5/2/8:19 3 Found 5/2/8:37 4 Found 5/2/8:49 Thank you Avi	[reply] [d/l] [select]
Re^5: Extract a pattern from a string by NetWallah (Canon) on Jun 11, 2012 at 13:54 UTC
Brilliant ! - $-[1] is already calculated in the regex (as @-), so yes, it is more efficient than pos+length. I hope life isn't a big joke, because I don't get it. -SNL	[reply]
Re^6: Extract a pattern from a string by avim1968 (Acolyte) on Jun 14, 2012 at 05:15 UTC
Re^3: Extract a pattern from a string by ambrus (Abbot) on Jun 10, 2012 at 22:14 UTC
Beware with such a use of `index</i>, it is incorrect for it won't give you the offset you want i +f the substring appears more than once in the input. Eg. <c> $ perl -E 'my $s="ME170-5/2/10-ME172-5/2/10-ME4028"; while ($s=~m\|(\d{ +1,2}/\d{1,2}/\d{1,2})\|g){++$x;say "$x Found $1:" . (index($s,$1)+1)}' 1 Found 5/2/10:7 2 Found 5/2/10:7 $ perl -E 'my $s="ME170-5/2/10-ME172-5/2/1-ME4028"; while ($s=~m\|(\d{1 +,2}/\d{1,2}/\d{1,2})\|g){++$x;say "$x Found $1:" . (index($s,$1)+1)}' 1 Found 5/2/10:7 2 Found 5/2/1:7 $` [download] Instead, if you really want to know the offsets, then use either the `pos` or the `@-` match variable to find where the regular expression has matched: `$ perl -E 'my $s="ME170-5/2/10-ME172-5/2/10-ME4028"; while ($s=~m\|(\d{ +1,2}/\d{1,2}/\d{1,2})\|g){++$x;say "$x Found $1:" . $-[1]}' 1 Found 5/2/10:6 2 Found 5/2/10:19 $ perl -E 'my $s="ME170-5/2/10-ME172-5/2/1-ME4028"; while ($s=~m\|(\d{1 +,2}/\d{1,2}/\d{1,2})\|g){++$x;say "$x Found $1:" . $-[1]}' 1 Found 5/2/10:6 2 Found 5/2/1:19 $` [download] However, maybe you don't want to know the positions at all, but instead match the port numbers and dates with a single regular expression that has two captures. Also, those newlines and plus signs inside the braces are just a mistake you made when pasting here, right?	[reply] [d/l] [select]
Re^4: Extract a pattern from a string by avim1968 (Acolyte) on Jun 11, 2012 at 04:03 UTC
Hi thank you for the warning, I just hit that problem during the run. when i got the same port number in a line. i'll modify my script again, with your input. thank you Avi p.s. all those newlines and plus signs inside the braces are not mine but were placed there after pasting the code.	[reply]