How do I search for the last occurence of a string?

gxw · 08-12-2009, 11:04 AM

Hi,

I have a file I need to do a fully scripted update to. Basically I need to insert a block of code AFTER the last occurrence of a particular string.

How would I go about doing that with sed or awk for example?

Any advice appreciated,
Thanks.

pixellany · 08-12-2009, 11:35 AM

Code:

num=$(grep -n <pattern> filename|tail -n1|cut -d: -f1);sed "$num a <string>" filename

replace <pattern>, <filename>, and <string> with your stuff.

$10 says that someone will produce a better answer before 12 noon PDT.......

pixellany · 08-12-2009, 10:47 PM

No-one took the bet!! You could have made an easy $10.....

And no-one had a better idea.....

And the OP is gone........

What is the world coming to??......

micxz · 08-13-2009, 12:16 AM

Quote:

Originally Posted by pixellany

Code:

num=$(grep -n <pattern> filename|tail -n1|cut -d: -f1);sed "$num a <string>" filename

replace <pattern>, <filename>, and <string> with your stuff.

$10 says that someone will produce a better answer before 12 noon PDT.......

Code:

num=`awk '/<pattern>/ { print NR }' filename | tail -1`; sed "$num a <string>" filename

Three commands is better than four. What a minute is three better than four? I know I still lost the bet'

gxw · 08-13-2009, 07:58 AM

Thanks to both of you. I'm sure the 1st one would work fine too, but I actually implemented the following and it worked a treat:

num=`awk '/<mystring>/ { print NR }' myfile | tail -1`
sed "$num a <my 1st Line>\n<my 2nd line>" <myfile >mynewfile

The us of NR and then tail is obviously the key, so thanks as that just didn't occur to me to do it that way!

pixellany · 08-13-2009, 08:14 AM

No....the key is to use SED, and then add kludges on top of it until it works..........

(micxz just has better kludges)

My method was to start with the first command that I could think of that would allow me to get to the last instance of the pattern---very scientific

micxz;
Noone took the bet, so there's nothing to win or lose!! (Actually, there's a loophole.....

)
Yes, your version is better------fewer characters to type and surely runs MUCH faster than mine......

micxz · 08-13-2009, 04:33 PM

Quote:

Originally Posted by pixellany

micxz;
Noone took the bet, so there's nothing to win or lose!! (Actually, there's a loophole.....

)

Your post was after the bet by time?

pixellany · 08-13-2009, 05:17 PM

I specified a time deadline but no date........

But, now I've spent the $10 on something else........