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Old 11-16-2012, 06:37 AM   #1
Adzrules
LQ Newbie
 
Registered: Oct 2012
Posts: 14

Rep: Reputation: Disabled
Remove lines based upon the previous line


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
 
Old 11-16-2012, 06:49 AM   #2
linosaurusroot
Member
 
Registered: Oct 2012
Distribution: OpenSuSE,RHEL,Fedora,OpenBSD
Posts: 982
Blog Entries: 2

Rep: Reputation: 244Reputation: 244Reputation: 244
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.
 
Old 11-16-2012, 07:18 AM   #3
mandyapenguin
Member
 
Registered: Nov 2011
Location: India
Distribution: RedHat, Cent OS, Fedora, Debian, Ubuntu
Posts: 106

Rep: Reputation: Disabled
This may help you
Code:
sed '/^FO*\|^RO*/!d' filename
 
  


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