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sed solution for condition checking


 
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# 1  
Old 07-21-2009
sed solution for condition checking

Hi all ,

Recently i came across this in FAQ's.

I have a file

Code:
cat rem.txt
sreedhar 20
sreedhar 10
sreedhar 15
sreedhar 18
sreedhar 16
sreedhar 30

I have to replace sreedhar with "Sridhar" if the second parameter is > 18.

I need to do it in "sed" only. I am wondering how this can be done.
# 2  
Old 07-21-2009
If you have gsed you can use egrep like syntax for matching multiple strings, ie.
Code:
(pattern1|pattern2|...)

If you want to stay compatible you can use:
Code:
sed -e '/ 19$/ {s/sreedhar/Sridhar/}' -e '/ [2-9][0-9]\+$/ {s/sreedhar/Sridhar/}' infile
Sridhar 20
sreedhar 10
sreedhar 15
sreedhar 18
sreedhar 16
Sridhar 30

In awk this would have been much easier and also with real arithmetics.
# 3  
Old 07-21-2009
Thanks zaxxon for the solution.

But it's not working as i am getting the error

Code:
Function / 19$/ { s/sreedhar/Sridhar/ } cannot be parsed.

Yes , i worked with awk and it's easy to do it in awk.

But sed's solution is seems to be cumbersome as we are not doing much like arithmetic operations.

Last edited by panyam; 07-21-2009 at 10:13 AM..
# 4  
Old 07-21-2009
With a little modification to above script, you can do this...
Code:
sed -n '
/ 19$/ {
   s/sreedhar/Sridhar/
   p
   }
/ [2-9][0-9]$/ {
   s/sreedhar/Sridhar/
   p
   }' file



---------- Post updated at 07:02 PM ---------- Previous update was at 07:00 PM ----------

If the number is negative or greater than 99... We need to tweak a bit more.
# 5  
Old 07-21-2009
Thanks Rakesh ...

I tried in the same way ,but .. As i was messing "-e" with "-n" there were some errors i was getting.

sed always makes me "sad" :|

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