grep for lines containg two variables

smoss74 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: grep for lines containg two variables by ikegami (Patriarch) on Dec 07, 2005 at 16:29 UTC
`@interesting_lines = grep /$string1/, grep /$string2/, @log;` [download] or `@interesting_lines = grep /$string1/ && /$string2/, @log;` [download] or `@interesting_lines = grep /^(?=.$string1)(?=.$string2)/, @log;` [download] OT Note: If your strings contain text, not regex, be sure to escape them using `quotemeta` or `/\Q$string\E/`. Better yet, use `index` instead of regexs in that case since it's much faster.	[reply] [d/l] [select]
Re^2: grep for lines containg two variables by l3v3l (Monk) on Dec 07, 2005 at 23:35 UTC
seems that lookahead grep is the slightly faster solution ... here is the test script I used: `#!/usr/bin/perl -w # usage : ./this_script.pl < input_file > captured_benchmarks use strict; use Benchmark; my @data=<>; my (@res1,@res2,@res3); timethese (100000000, { grep_and => q{ @res1 = grep /GGGGGACACCTTCTCTCTCT/ && /RH_MEa0001bG06/, @data; }, double_grep => q{ @res2 = grep /GGGGGACACCTTCTCTCTCT/,grep /RH_MEa0001bG06/,@data; }, lookahead_grep => q{ @res3 = grep /^(?=.GGGGGACACCTTCTCTCTCT)(?=.RH_MEa0001bG06)/,@da +ta; } } );` [download] ... and the results `Benchmark: timing 100000000 iterations of double_grep, grep_and, looka +head_grep... double_grep : 27 wallclock secs (26.98 usr + 0.00 sys = 26.98 CPU) @ 3705899.79/s ( +n=100000000) grep_and : 24 wallclock secs (23.05 usr + 0.00 sys = 23.05 CPU) @ 4338959.52/s ( +n=100000000) lookahead_grep : 24 wallclock secs (22.83 usr + 0.00 sys = 22.83 CPU) @ 4380585.25/s ( +n=100000000)` [download]	[reply] [d/l] [select]
Re^3: grep for lines containg two variables by ikegami (Patriarch) on Dec 08, 2005 at 01:09 UTC
I wish I had a computer that executed 4380585.25 greps per second... Your test is useless. The @data, $string1 and $string2 used by the test are always undef. I fixed it up below. Note the use of `sub { ... }` instead of `q{ ... }`. Subs capture over `my` variables, while the string is `eval`ed in a different scope where the `my` varibles don't exist. `#!/usr/bin/perl use strict; use warnings; use Benchmark qw( cmpthese ); my $string1 = qr/tr/; my $string2 = qr/e/; my @data = do { open(my $fh, '<', $0) or die; <$fh> }; cmpthese (-3, { grep_and => sub { my @r = grep /$string1/ && /$string2/, @data; return @r; }, double_grep => sub { my @r = grep /$string1/, grep /$string2/, @data; return @r; }, lookahead => sub { my @r = grep /^(?=.$string1)(?=.$string2)/, @data; return @r; } });` [download] outputs `Rate lookahead double_grep grep_and lookahead 8114/s -- -52% -62% double_grep 16986/s 109% -- -21% grep_and 21483/s 165% 26% --` [download] The contents of @data are probably not all that good, so the figures aren't perfect, but they give a pretty good idea.	[reply] [d/l] [select]
Re^4: grep for lines containg two variables by l3v3l (Monk) on Dec 08, 2005 at 17:54 UTC
Re^5: grep for lines containg two variables by ikegami (Patriarch) on Dec 08, 2005 at 18:35 UTC
Some notes below your chosen depth have not been shown here
Re^2: grep for lines containg two variables by tweetiepooh (Hermit) on Dec 08, 2005 at 14:12 UTC
Just a couple of queries... What if one string is contained in the other but should not be counted? Ok so add white space checks/breaks to the search strings. Do you need to lookahead on both strings? This seems to work. `@interesting_lines = grep /(?=.$string1).$string2/,@log;` [download]	[reply] [d/l]
Re^3: grep for lines containg two variables by ikegami (Patriarch) on Dec 08, 2005 at 15:07 UTC
What if one string is contained in the other but should not be counted? That's tricky. Do you really want that? I don't have the time right now to spend the effort on a what-if you won't use. Do you need to lookahead on both strings? No, it's optional on the last one. If you had 4 strings, you'd need the lookahead on the first three, but it would be optional on the fourth.	[reply]
Re^4: grep for lines containg two variables by tweetiepooh (Hermit) on Dec 08, 2005 at 16:27 UTC
Re^3: grep for lines containg two variables by ikegami (Patriarch) on Dec 08, 2005 at 18:16 UTC
What if one string is contained in the other but should not be counted? How about `grep /$string1.$string2\|$string2.$string1/,` [download]	[reply] [d/l] [select]
Re: grep for lines containg two variables by gjb (Vicar) on Dec 07, 2005 at 16:41 UTC
`@interesting_lines = grep {/$string1/ xor /$string2/} @log;` [download] will do nicely. Hope this helps, -gjb- Update: apparently I got the question wrong, see the previous answer or for an alternative syntax: `@interesting_lines = grep {/$string1/ and /$string2/} @log;` [download]	[reply] [d/l] [select]
Re^2: grep for lines containg two variables by ikegami (Patriarch) on Dec 07, 2005 at 16:50 UTC
When the OP said I know the syntax for "or" (code example) but not "and" I think he meant I know the syntax for "or" (code example) but I don't know the syntax for "and" rather than I don't know the syntax for "or but not and"	[reply]
Re^3: grep for lines containg two variables by reasonablekeith (Deacon) on Dec 07, 2005 at 16:57 UTC
Anyone else reminded of the Friends episode. They don't know that we know they know we know! (Joey just shakes his head. ... --- my name's not Keith, and I'm not reasonable.	[reply]
Re^2: grep for lines containg two variables by reasonablekeith (Deacon) on Dec 07, 2005 at 16:45 UTC
I'm glad someone else made this mistake, It must be something about how the question is worded because this is also what I thought the OP was after. It's completely wrong though. [id://ikegami] got it right. ++ for effort anyway :) --- my name's not Keith, and I'm not reasonable.	[reply]
Re: grep for lines containg two variables by pileofrogs (Priest) on Dec 07, 2005 at 18:56 UTC
Does one string always preceed the other string? Or can they be in any order? If I've got my head screwed on correctly (always a doubtful proposition,) some of the solutions above will work in both cases and other solutions will only work if $string1 appears before $string2. From ikegami's post: Works in any order `@interesting_lines = grep /$string1/, grep /$string2/, @log;` [download] Works in any order `@interesting_lines = grep /$string1/ && /$string2/, @log;` [download] Only works if $string1 preceeds $string2 `@interesting_lines = grep /^(?=.$string1)(?=.$string2)/, @log;` [download] Or am I a total moron?	[reply] [d/l] [select]
Re^2: grep for lines containg two variables by Roy Johnson (Monsignor) on Dec 07, 2005 at 19:02 UTC
Because it's done with lookaheads, the last example works with strings in either order. That is, in fact, why it is done with lookaheads. In my mind, lookaheads like this are the "and" that complements alternation's "or" in regexen. Caution: Contents may have been coded under pressure.	[reply]
Re^3: grep for lines containg two variables by pileofrogs (Priest) on Dec 07, 2005 at 21:12 UTC
Woah! Thanks!	[reply]


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