sed solution for condition checking

Shell Programming and Scripting
1

Hi all ,

Recently i came across this in FAQ's.

I have a file

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

If you have gsed you can use egrep like syntax for matching multiple strings, ie.

(pattern1|pattern2|...)

If you want to stay compatible you can use:

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

Thanks zaxxon for the solution.

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

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.

4

With a little modification to above script, you can do this...

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

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" :expressionless: