Print 4 Lines below matching criteria

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

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Re: Print 4 Lines below matching criteria by cLive ;-) (Prior) on Nov 16, 2006 at 05:10 UTC
`m/ \nid: # match new line followed by id: [^\n]* # 0 or more characters that are not new lines \n # a newline ([^\n]*\n){4}) # the next 4 lines and store in $1 /sx; # treat as a '(s)ingle line' and (x) ignore whitesp +ace` [download] edit - I was sober too - omg, back to Idiocy for Dummies...	[reply] [d/l]
Re^2: Print 4 Lines below matching criteria by ikegami (Patriarch) on Nov 16, 2006 at 05:56 UTC
Oops, you forgot to negate your character classes! Also, the `s` option is useless because `.` wasn't used. `m/ \n id: # Match new line followed by id: [^\n]* # 0 or more characters that are not new lines \n # A newline ([^\n]*\n){4}) # The next 4 lines and store in $1 /x; # Ignore whitespace` [download]	[reply] [d/l] [select]
Re: Print 4 Lines below matching criteria by McDarren (Abbot) on Nov 16, 2006 at 06:34 UTC
Update: my apologies - this does not actually work correctly - see replies below. For something a little more verbose: `#!/usr/bin/perl -w use strict; while (<DATA>) { if (/^id:/) { my ($city, $phone, $street, $zip) = (<DATA>,<DATA>,<DATA>,<DAT +A>); print "$city$phone$street$zip"; } } __DATA__ John, Doe Michael id:1234567890123 library:ACME City, state:PUEBLO, CO Phone:719-555-555 Street:1610 Sorrow AVE APT D Zip: 81004` [download] Prints: `City, state:PUEBLO, CO Phone:719-555-555 Street:1610 Sorrow AVE APT D Zip: 81004` [download] Cheers, Darren	[reply] [d/l] [select]
Re^2: Print 4 Lines below matching criteria by chromatic (Archbishop) on Nov 16, 2006 at 06:43 UTC
I didn't realize those readline calls would be in scalar context there. How interesting. Very nice! Update: I wrote a bad test case at nearly 11 pm. Sorry for the confusion!	[reply]
Re^3: Print 4 Lines below matching criteria by jwkrahn (Abbot) on Nov 16, 2006 at 07:53 UTC
They are not in scalar context. To be in scalar context you would need to do: `my ( $city, $phone, $street, $zip ) = ( scalar <DATA>, scalar <DATA>, +scalar <DATA>, scalar <DATA> );` [download]	[reply] [d/l]
Re^4: Print 4 Lines below matching criteria by BrowserUk (Patriarch) on Nov 16, 2006 at 08:37 UTC
Re^4: Print 4 Lines below matching criteria by McDarren (Abbot) on Nov 16, 2006 at 08:19 UTC
Re^2: Print 4 Lines below matching criteria by Anonymous Monk on Nov 16, 2006 at 23:33 UTC
Darren - Thanks for your help, I used the script you suggested and it works great. DG	[reply]
Re: Print 4 Lines below matching criteria by GrandFather (Saint) on Nov 16, 2006 at 06:47 UTC
If what you want are the lines fron "id:" to "Zip:" then: `m/^id:/ .. m/^Zip:/ and print while (<INFILE>);` [download] does the trick. DWIM is Perl's answer to Gödel	[reply] [d/l]
Re: Print 4 Lines below matching criteria by Anonymous Monk on Nov 16, 2006 at 09:44 UTC
Never be afraid to reuse code! Simplest Perl script to do this: `perl -e 'system "grep -A 3 ^id: $ARGV[0]"' file` [download] Or as a non-perl command: `grep -A 3 ^id: file` [download] This might require you to install (GNU) grep, but luckely, that has ported to a wide range of platforms.	[reply] [d/l] [select]
Re: Print 4 Lines below matching criteria by jbert (Priest) on Nov 16, 2006 at 09:58 UTC
This code does it in a fairly straightforward way (although I like the grep solution best). `#!/usr/bin/perl use strict; use warnings; my $line; my $num_lines = 0; while ($line = <DATA>) { $num_lines = 4 if $line =~ /^id:/; if ($num_lines > 0) { print $line; $num_lines--; } } exit 0; __DATA__ John, Doe Michael id:1234567890123 library:ACME City, state:PUEBLO, CO Phone:719-555-555 Street:1610 Sorrow AVE APT D Zip: 81004 Jane, Doe Michael id:1234567890124 library:ACME City, state:PUEBLO, CO Phone:719-222-555 Street:1610 Happy AVE APT D Zip: 81006` [download] Andas the one-liner it started out as (much love for -n and $_ in the right context): `perl -n -e '$n = 4 if /^id:/; if ($n) { print; $n--; }' your_data_file` [download]	[reply] [d/l] [select]
Re: Print 4 Lines below matching criteria by fenLisesi (Priest) on Nov 16, 2006 at 10:06 UTC
The following might get you started. Cheers. `use strict; use warnings; while (my $line = <DATA>) { if ($line =~ /^id:\d+/) { for (1 .. 4) { my $following = <DATA>; print $following; } } }` [download] Read more... (855 Bytes) Update: Sorry, jbert, your post was not on yet when I started.	[reply] [d/l] [select]
Re^2: Print 4 Lines below matching criteria by johngg (Canon) on Nov 16, 2006 at 11:30 UTC
I tend to use scalar file reads when appropriate so as to avoid temporary variables so I would write your `for (1 .. 4) { my $following = <DATA>; print $following; }` [download] like this `print scalar <DATA> for 1 .. 4;` [download] It just looks a little cleaner to me. Cheers, JohnGG	[reply] [d/l] [select]
Re^2: Print 4 Lines below matching criteria by Anonymous Monk on Nov 16, 2006 at 10:41 UTC
Small issue with your program: it will generate warnings if there's an 'id:' string in the last 4 lines of the file, as it will try to read past the end of the file.	[reply]