On 11/02/2016 10:52 AM, Bruce Dubbs wrote: >> >> I want that the research is done only in the underline characters. So >> what I have to add in grep command to put the limit of 30 characters? > > cut -c 30 filename | grep ACGTAC
That works if you are only interested in seeing the first 30 characters of a given line, rather than printing the entire line when the match was only within the first 30 characters. If you need to map back to the entire line, you can use some sort of decorate-search-undecorate algorithm to keep the search portion still under grep, but at that point, it's probably easier to just write it all in a language that can do it in a single pass. I guess I should also mention that if you know your lines are a fixed width (say for example that every line is exactly 80 characters), then you can exploit that using just grep to find a match only in the first 30 characters by explicitly spelling out the fixed-width remainder of the line as an anchor: grep 'ACGTAC.*.\{50\}$' filename Sadly, the two example lines you printed were not the same length, so I don't think it helps for your case. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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