shell - sed command replacing string that contains special character is not working -


I want to change a particular string inside file.txt. My string is like this:
old string 

  tech = / lsf / dfg / avi, / ldf / fgh / vv

-> New string 

  technology = $ var

I have tried the following 

  sed -i 's / tech

P> 
  Sed -i's #technology = / lsf / dfg / avi, / ldf / '#' (or else another character which Not in the string) with CAD Replace the delimiter '/' for the expression. You are trying to match and change).

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