sed: remove first character from particular line

Shell Programming and Scripting
1

Hello Experts,

I have a file "tt.txt" which is like:

#a1=a2
b1=b2
#c1=c2

I need to remove the pound (#) sign from a particular line. In this case let us assume it's 3rd line : "#c1=c2"

I can do it through:

sed "s/#c1=c2/c1=c2/" tt.txt

but it is possible that I may not know the value "c2" due to which I would not be able to use the above command.

Please point me in the right direction.

Thank You.

Regards,
HKansal

2

At least you have to know on what line or how to recognize the particular line (pattern?).

Regards

3

Hello,

Yes Franklin, as rightly said by you, that I can identify. The "c1" part is the only thing that I would know and it is unique, so locating the line is not a problem.

I want to make my substitution independent of the "c2" part.

Thank You.

Regards,
HKansal

4 
awk '
/^#c1/{sub(/^#/,"")} # use when uncomment
/^c1/{sub(/^c1/,"#c1")}#use when want to comment
1' file
5

Hello,

Hey Ghostdog, that worked as good as you were sure about it. Thanks.
Also, for letting me know something more about "awk".

Any way to do it through sed, just for my information and learning!

I'll put up the complete script soon as I've been asking a lot of small questions, all to get through a composite script.

Thank You.

Regards,
HKansal

6 
sed 's/^#c1/c1/' file # to uncomment
sed 's/^c1/#c1/' file # to comment
7

Hello,

I am posting the final script created under the initial thread :here:

Thank You

Regards,
HKansal