Remove lines based upon the previous line

Adzrules · 11-16-2012, 05:37 AM

Hi everyone,

I have the following text in a document:

Code:

LF82_762
F0 	GCGGATTTTATTTTATTAAG
LF82_784	
LF82_539	
F0	ATGAGTAAGCGGATGCATTCTC
R0	AGTTCAGAAGCTGAAGCAGAAA
LF82_2826	
F0	ATGGATTTCGACACAATCATGGA
R0	AGCCGTTAGATTTTGCCGA
LF82_672
LF82_749
LF82_3653	
R0	AAATTATTTTATTAAGTGTAAAACAGTTAACGACTATCGC
LF82_442
F0	ATGTTCGCGGGATCGTGTGGGTCGATGC

I would like to remove any lines that are NOT followed by a line containing an F0 AND then a line with an R0, so that the resulting text looks like this:

Code:

LF82_539	
F0	ATGAGTAAGCGGATGCATTCTC
R0	AGTTCAGAAGCTGAAGCAGAAA
LF82_2826	
F0	ATGGATTTCGACACAATCATGGA
R0	AGCCGTTAGATTTTGCCGA

I initially thought of using awk, but the syntax is a bit confusing. Any suggestions?

Thank you to all

Adzrules

linosaurusroot · 11-16-2012, 05:49 AM

Logic first and syntax later. Sketch your state machine on a piece of paper starting from a "start" state where you have opened the file but not done anything yet. Then the program in awk or something else will start to become clear.

mandyapenguin · 11-16-2012, 06:18 AM

This may help you

Code:

sed '/^FO*\|^RO*/!d' filename