Using sed to insert text into a string matching string

Question

I have a line in a text file containing a list of elements assigned to a variable ...

ITEMS="$ITEM1 $ITEM2 $ITEM3"

And I would like to write a bash script that uses sed to search for a string matching ITEMS and adds another element to the end of the list in double quotes, so it leads to ...

ITEMS="$ITEM1 $ITEM2 $ITEM3 $ITEM4"

In addition, I have the number of the element to be added, stored in a variable, say, this is the number $. So I'm trying to get him to add $ ITEM4 $ number and replace it with the number assigned to this variable, and let it be 4 in this case. How could I do this? Thanks!

Answer 1

$ cat file
ITEMS="$ITEM1 $ITEM2 $ITEM3"
$ number=4
$ sed "/ITEMS/s/\"$/ \$ITEM$number&/" file
ITEMS="$ITEM1 $ITEM2 $ITEM3 $ITEM4"

Answer 2

:

num=4
sed "/ITEMS=/s/\"$/ \$ITEM${num}\"/"

• sed /re/s/before/after/, re (, a grep), s///
• \s - , * 0 (-)
• & ,
• ^, /
• $, /