[SOLVED] awk:searching for a pattern and remove everything before it

lcvs · 06-25-2012, 10:32 PM

Hi all !

I am trying with awk to search for lines matching one of 2 patterns in the 2nd field, and returns only the lines with the pattern + everything after it in this field (= removing everything before the pattern in the field).

input (pattern 1 in red, pattern 2 in blue):

Code:

AAA|bbbbbZXCVjhkjhkjhk|DDDDDDDD
AAAAAA|jtyfytthyhyRTYUewertyu|OOOOOOOOO

output:

Code:

AAA|ZXCVjhkjhkjhk|DDDDDDDD
AAAAAA|RTYUewertyu|OOOOOOOOO

I was thinking using 2 gensub commands for each pattern:

Code:

gensub(/(.*)(pattern1)(.*)/,"\\2\\3","g",$2)
gensub(/(.*)(pattern2)(.*)/,"\\2\\3","g",$2)

But is there a way to write it only with one command?

Thanks for your help !

Jebram · 06-26-2012, 02:15 AM

Try regexp group alternatives:

Code:

gensub(/(.*)(pattern1|pattern2)(.*)/,"\\2\\3","g",$2)

lcvs · 06-26-2012, 09:16 PM

Thanks Jebram !

Before I tried with "||" instead of "|", it works now !

lcvs · 06-27-2012, 01:38 AM

Actually, it doesn't work...

It takes only pattern2 but doesn't change anything when there is pattern1 !

output:

Code:

AAA|bbbbbZXCVjhkjhkjhk|DDDDDDDD
AAAAAA|RTYUewertyu|OOOOOOOOO

And when I write the patterns between braces:

Code:

awk 'BEGIN{FS=OFS"|"} {gensub(/^(.*)((pattern1)|(pattern2))(.*)$/,"\\2\\3","g",$2)}1' input

It doesn't change anything when it matches pattern1, and only conserve pattern2 when it matches pattern2:

Code:


	Code:
	AAA|bbbbbZXCVjhkjhkjhk|DDDDDDDD
AAAAAA|RTYU|OOOOOOOOO

I don't know if it is a problem of syntax or if this command can handle several patterns at once !!!!

lcvs · 06-27-2012, 02:20 AM

I also tried with a regex for the 2 patterns:

Code:

awk 'BEGIN{FS=OFS"|"} {gensub(/^(.*)([ZR][XT][CY][VU])(.*)$/,"\\2\\3","g",$2)}1' input

Surprisingly, it works only when the field matches pattern2 (and returns the entire string when it matches pattern1).

Help would be welcome... :-)

grail · 06-27-2012, 03:16 AM

How about:

Code:

awk 'BEGIN{OFS=FS="|"}match($2,/(ZXCV|RTYU)/,f){split($2,a,f[1]);sub(a[1],"",$2);$1=$1;print}' file