How to use sed to replace a pattern in a file only in lines that contain another pattern

In my specific situation, I need to loop through several hundred files that contain a variable which stores a URL. All of the URLs are different, but for the sake of this example we can assume they all end with 'com"' I need to add some text immediately following the com Because all of the URLs will have different domains I cannot use a sed command like: ``` sed -i 's/^ENVIRONMENT="someurl.com"/ENVIRONMENT="someurl.com.origin.net"/g' ``` Because the files contain other lines which may contain com, I cannot use something like: ``` sed -i 's/com/com.origin.net/g' ``` I need to do this search and replace only on a specific line containing a pattern, such as from my example below in regex: ``` ^ENVIRONMENT.* ``` If I could focus the use of sed only to the line that matched the above pattern then I could use some adaptation of sed such as `sed -i 's/com/com.origin.net/g'`. I could of course write an overly complicated bash script to do this, but I know there is a nice one liner way to tell sed to find a pattern, only work on the line that the pattern is found in, and search and replace another pattern with a new string. In searching Google, the only semi relevant link I found about this was: How to sed only that lines that contains given string?. But it didn't sufficiently answer my question. Also being able to constrain sed in general to just a line that matches a pattern would by a nice tool to add to me sed arsenal. Any help that leads to solution here will be very appreciated. Here is an example of a file ``` ### Example File # # # someurl.com ENVIRONMENT="someurl.com" ``` I want to replace `ENVIRONMENT="someurl.com"` with `ENVIRONMENT="someurl.com.orign.net"`