Shell Programming and Scripting

Hi,
I have to insert a line at a particular line number in my file. But the line number is not fixed and it will vary every time. So, I have to use a variable to get the line number

I know we can use sed to insert lines at a particular line number but it does not work with variable substitution.

Ex:

Code:

sed '1i\
xxxx' file

The above code works. But the below one does not work.

Code:

n=2
sed '$n i\
xxxx' file

How to handle this variable substitution using sed. I am also ok with any solution without using sed.

Thanks,
Sugan

The "problem" are the quotes. With single quotes, the shell doesn't do any substitution of variables, but instead uses the literal string. 3 possible solutions:

Code:

n=2
sed "$n i\
xxxx" file

Code:

n=2
sed $n' i\
xxxx' file

Code:

n=2
sed "$n"' i\
xxxx' file

Code:

sed ${linenumber}a\ "Added Insert Your Line" file

--> Append

Code:

sed ${linenumber}i\ "Added Insert Your Line" file

--> Insert

Thanks a lot Pludi. Your solution works!!!