[SOLVED] sed program to replace strings starting with a specific character

Issue

I know similar questions have been asked around, like for example here, but I've been unable to reproduce desired results for my own needs with such examples, and I don't understand why.

I want to replace all words in a file starting with the character '@' by <@MENTION>. For example, this:

I have 6 @emailaddresses and 10% of the people don't eat sandwiches! I have six @emailaddresses and 10%... @123_Username @BAPP, you shouldn't say that! I recently called@User but he didn't answer. @Username is not a nice person! This @username guy is really cool!

Should become this:

I have 6 <@MENTION> and 10% of the people don't eat sandwiches! I have six <@MENTION> and 10%... <@MENTION> <@MENTION>, you shouldn't say that! I recently called@User but he didn't answer. <@MENTION> is not a nice person! This <@MENTION> guy is really cool!

I have tried this:

sed 's/@[a-zA-Z0-9_]*/<@MENTION>/'

But the string '@BAPP' is not taken into account, which I'd like to, and 'called@User' is taken into account, which I would prefer to avoid.

I also tried this:

sed -E -e 's/\b@[a-zA-Z0-9_]*\b/<@MENTION>/'

But for a reason I don't know the word boundaries are not taken into account...

Any help to help me understand my way around this would be much appreciated, as I'm (obviously) learning and have a limited experience with Bash. Thanks a lot in advance.

Solution

One sed idea:

$ sed -E 's/(^|[^[:alnum:]])@[a-zA-Z0-9_]*/\1<@MENTION>/g' file

NOTE: the initial ^ was added to address the case where the desired string is at the beginning of the line.

This generates:

# assuming embedded linefeeds

I have 6 <@MENTION> and 10% of the people don't eat sandwiches! I have six
<@MENTION> and 10%... <@MENTION> <@MENTION>, you shouldn't say that! I recently
called@User but he didn't answer. <@MENTION> is not a nice person! This <@MENTION> guy
is really cool!

# assuming no embedded linefeeds

I have 6 <@MENTION> and 10% of the people don't eat sandwiches! I have six <@MENTION> and 10%... <@MENTION> <@MENTION>, you shouldn't say that! I recently called@User but he didn't answer. <@MENTION> is not a nice person! This <@MENTION> guy is really cool!

Answered By - markp-fuso

Answer Checked By - Marie Seifert (WPSolving Admin)