Bashscripts.org

Hi,
I have a file which contains usernames, number of them:

I need for example to find the string (we do not know what the text is after colon): and replace with
I am trying to use something like this:

but of course it's not working.
I googled some time and still can't find solution.
Thank you.

Hi Lush!

I sure hope you've found an answer to this by now, but I think I see the problem. In your 'sed' command, the search string you're using is 'user2: *'. What this matches is 'user2:' followed by any number of spaces. Using your example, the result is that it ADDS 'root' in before the existing data:



So, if what you really want to do is replace that entire line, you have to use the "." wildcard. The dot means "Any Single Character". The asterisk doesn't behave like you'd expect it to in regular expressions. It means that the character before it can repeat until infinity and it'll keep matching it.

So in your example, you're matching an infinite number of "spaces" with " *". To match ANY character, not just spaces, you'll want to use the dot.



That should give you the result you're looking for. I hope this helps!

-Jeo

Thank you so much, Jeo!
Especially for the detailed explanation for newbie)) That's appreciated.

Could you guide me how to pass a variable to the sed regular expression? Like:
I tried different ways. As to the topic:
http://www.unix.com/shell-programming-scripting/23292-passing-variables-sed-inside-script.html
they solve this with awk. Any ways to code the expression with sed?

Just do not use single quotes on your variables:

If $user2 can contain some weird characters (spaces, dots, $, etc.), you can add double quotes around it.

That's it. Thank you very much.