Homework & Coursework Questions

here's my statement:

Code:

sed -i '4s/$/ #/' sed_test_file.txt

I want to edit the n'th line (the '4' is for the example) of the file (but you can't just put the n instead of the 4)

sed_test_file is a simple text file containig text only

I tried to use $urlCounter instead of 4, as urlCounter is a variable modified with every iteration. no success there

Ben Gurion University
Be'er Sheva
Israel
Dr. A. Goldfeld
Course Num 371.1.2473

For this simple sed programme, you could use double quotes and thus have your shell variable expand in the string passed to sed. You'll need to be careful and escape the dollar sign so that the shell doesn't try to expand it.

However, if you are going to end up making multiple passes across the same text file, there might be a more efficient way than lots of sed processes.

Example with double quotes and escapes:

Code:

line=4
sed -i "${line}s/\$/ #/" sed_test_file.txt

Hi ganraveh,

I don't know whether i understand your requirement currectly or not.
you can make a shell script, something like this:

Code:

bash-2.03$ cat sd.sh
echo "enter line number: "
read n
sed ''$n's/$/ #/' r2.txt

when u run the script, it will ask for the line no.

regards,

"However, if you are going to end up making multiple passes across the same text file, there might be a more efficient way than lots of sed processes.

Example with double quotes and escapes:

Code:

line=4
sed -i "${line}s/\$/ #/" sed_test_file.txt

[/QUOTE]

thanks for the help! it works as i wanted. but now i'm curious: how could it run more efficiently?

Glad that it works. My efficiency comment was based on the assumption that you were invoking sed multiple times -- I could be wrong as you might not be doing this at all, it seemed to me from your request that you might. To make a more precise comment about it I (we) would need to see the relevant parts of the script.