bash - Expand variables in sed

Question

I need use sed into bash script, for add lines after any line numer of script with some pair of values (below work)

sed -i.bak '14isome_text=some_text' file

But I need on script bash (sh) for expand variables (below not work)

sed -i.bak '$number_linei$var1=$var2' $var3

Answer 1

Just use double quotes instead of single quotes. You'll also need to use {} to delimit the number_line variable correctly and escape the , too.

sed -i.bak "${number_line}i\$var1=$var2" $var3

I'd personally prefer to see all of the variables use the {}, ending up with something like:

sed -i.bak "${number_line}i\${var1}=${var2}" ${var3}