bash - Using sed to insert text at end of line matching string

Question

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

ITEMS="$ITEM1 $ITEM2 $ITEM3"

And I would like write a bash script that uses sed to find the line matching ITEMS and append another item to the end of the list within the double quotes, so it results in ...

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

Furthermore, I have the number of the item to add stored in a variable, let's say it's $number. So I'm trying to get it to add $ITEM4$number and have it replace $number with whatever I assigned to that variable, let's say it's the number 4 in this case. How could I best accomplish this? Thanks!

Answer 1

Try this :

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

Explanations

• the sed form used here is /re/s/before/after/ where re is a regex (like a grep), s/// is substitution
• s is a space and * mean 0 ore more occurence(s)
• & stands for the string matched in the left part of the substitution
• ^ as first character of a regex means start of string/line
• $ as last character of a regex means end of string/line