Matching strings even if they start with white spaces in SED -

I'm having trouble matching strings even if they start with any number of white spaces in regular expression It has been a very short time since starting to use, so I need some help

Here is an example. I have a file (file.txt) which has two rows

  # string1 = 'test one' string1 = 'test two'  

I am trying to change the value of the second line without affecting row 1, so I used it

  sed -i "s | string1 =. * $ | String 1 = ' Test three '| g " 

It changes the values ​​of both lines, how can I change only the value of the second string?

thanks

With gnu sed, you can \ s , while other SAL implementations usually work with the [[: space:]] character group. Therefore, choose one of these:

  sed 's / ^ \ s * AWord / AnotherWord /' sed 's / ^ [[space:]] * AWord / AnotherWord /'  

Since you are using -i , I agree to GNU sed in any way, you probably should not re-type your word, because it is a Introducing the possibility of typos I had to go with it:

  sed -i "s / ^ \ (\ s * string1 = \). * / \ 1 'new value' / "File  

if you do not preserve leading whitespace You want to move out of the legs \ s * .