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This question already has an answer here:

I have a environment variable called NAME

export NAME="xyz"

and inside a file test.txt , I have a line

name=$NAME

I read the file and assigned the line to a variable y

y=`cat test.txt`

Now I am printing the variable y

echo $y

How can I get an output of name=xyz instead name=$NAME?

marked as duplicate by steeldriver, Jeff Schaller, roaima, G-Man, mdpc Jan 19 '18 at 1:29

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • where is your export NAME="xyz"? – WEBjuju Jan 18 '18 at 15:31
  • export NAME="xyz" is in the bash shell session , name=$NAME is in the file – Jobs Jan 18 '18 at 15:33
  • have you looked at this solution? – WEBjuju Jan 18 '18 at 15:35
  • Are you wanting to refactor and not use the exported environmental variable? Your problem is not entirely clear. – 111--- Jan 18 '18 at 15:36
  • That is not seems simple explanation for beginners like me – Jobs Jan 18 '18 at 15:37
2

I think you need to implement eval for this particular usage. I'll explain using the command line:

  1. export $ABC (as you export $NAME)

    $ grep ABC .bashrc
    export ABC="xyz"
    
  2. set the variable in your txt file

    $ cat test.txt
    name=$ABC
    
  3. set the $y variable to the output of cat test.txt

    $ y=`cat test.txt`
    
  4. eval $y

    $ eval $y
    
  5. now name is set:

    $ echo $name
    xyz
    
  • thx @datUser for the edit – WEBjuju Jan 18 '18 at 16:21
  • Hi, What I need is, a string , name=xyz . envsubst is a solution , but I found some example where a file is given as argument to it. Can we give the variable $y as input to envsubst program – Jobs Jan 23 '18 at 10:39
  • You have not explained well why you need to do what it is you are doing. – WEBjuju Jan 23 '18 at 18:34
  • I have to read the line name=$NAME from a file and reaplce the env variable $NAME in it and would get a result of name=xyz (consider that value of NAME in env is xyz) as output. I am using this output to grep another string. – Jobs Feb 5 '18 at 5:21

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