Change variable value inside text file with Sed

Question

I have a text file containting this

Var1=ofzer
Var2=smelf
..
..
VarN=mskfm

I want to change the value of one of my variables using Sed. How is that possible?

Solution 1

Say you wanted to change the value of Var2 from 'smelf' to 'smurf', you could use:

bash$ sed -i 's/Var2=.*/Var2=smurf/' file.txt

Solution 2

In case you want more complex substitution:

sed_param=s/Var1=.*/Var1=${NEW_VALUE}/  
sed -i "$sed_param" file.txt

Comments

[Olie]

Suppose I want to set it to ${NEW_VALUE}? I can't use ${var} inside of single quotes and, if I switch to double-quotes, the .* part doesn't work (does it?!) So now what?

[Alberto Salvia Novella]

You can use double quotes.