File1 is

```
var=10

```

File2 is

```
source File1

echo $var     #this displays 10 if I ran the shell. 

```

What goes here? I can’t get sed to work because I can use the variable inside the sed command,

```
$ sed -i ‘s/echo $var/var=$((var+10))/‘ File1`

```

I’ve tried all different combinations. I know this is bad code but I don’t have a better why to explain.

```
source File1

echo $var # I want this to display 20

```

I would like to alter File1 from File2 so I can add 10 to the value. Changing the results from 10 to 20 at the end of File2.

I’m open to all work arounds. I’m trying to create a character sheet for Dungeons and Dragons that tracks my HP among other things.