CODEWITHSUNDEEP
grep
user1898525
user1898525

Reputation: 133

How can I find files that match a two-line pattern using grep?

I created a test file with the following:

<cert>
</cert>

I'm now trying to find this with grep and the following command, but it take forever to run. How can I search quickly for files that contain adjacent lines like these? 

tr -d '\n' | grep '<cert></cert>' test.test

Upvotes: 0

Views: 96

Answers (1)

alexis
alexis

Reputation: 50220

So, from the comments, you're trying to get the filenames that contain an empty <cert>..</cert> element. You're using several tools wrong. As @iiSeymour pointed out, tr only reads from standard input-- so if you want to use it to select from lots of filenames, you'll need to use a loop. grep prints out matching lines, not filenames; though you could use grep -l to see the filenames instead.

But you're only joining lines because grep works one line at a time; so let's use a better tool. Here's how to search with awk:

awk '/<cert>/ { started=1; } 
   /<\/cert>/ { if (started) { print FILENAME; nextfile;} }
 !/<cert>/ { started = 0; }' file1 file2 *.txt

It checks each line and keeps track of whether the previous line matched <cert>. (!/pattern/ sets the flag back to zero on lines not matching /pattern/.) Call it with all your files (or with a wildcard like *.txt).

And a friendly suggestion: Next time, try each command separately (you've been stuck on this for hours and you still don't know what grep does?). And have a quick look at the manual for the tools you want to use. Unix tools are usually too complex for simple trial and error.

Upvotes: 1

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