Grepping multiple lines at once?

[Arndt]

edit doesn't work matches 1 2 2 3

ugly but it uses only grep
grep -A 3 -E "^1$" test.txt | grep -E "^2$" -B 1 -A 1 | grep -E "^3$" -B 2
count by grepping again: grep "\-\-" | wc -l (+ 1)

non-regex python:

import io

file = io.open("test.txt")
c = 0 
for l in file:
  if l == "1\n" and file.next() == "2\n" and file.next() == "3\n":
    c += 1

print(c)

This doesn't match

1
1
2
3

[amauk]

I'm not sure that grep can handle a line millions of characters long. Maybe it can, though.

Personally, I would write a small program for this purpose.

Grep (or any of the standard text stream utilities) can handle any sized input

[durand]

Cheers for the python stuff. It would have worked for my problem when it matched 21 2 3 because what I didn't really tell you was that every number was a decimal between 0 and 1. But in any case, the reason I was doing that was because I was trying to find the periodicity of the rand() c function which further research tells me is 2^32 ~= 4 billion and I couldn't create a file with 9 billion values (to get the period twice) without my hard drive or grep complaining so either way, it was impractical.

Python would have been even worse really but I guess if I left it long enough, it would have worked. Anyway, those snippets are quite useful for other things so I'll keep this thread in mind.

Thanks everyone!