Linux environment variable substitution

Question

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?

export NAME="xyz" is in the bash shell session , name=$NAME is in the file — Jobs, Jan 18 '18 at 15:33
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
@datUser i'm gathering that his env variable is not available in the shell script. i asked him where he set it, but the question was misunderstood. — WEBjuju, Jan 18 '18 at 15:38
If the environmental variable is causing you grief, I would suggest trying something more simple like passing the value you need from the system as a shell argument, ./script.sh someArgument and accessing it with $1. — 111---, Jan 18 '18 at 15:45
I don’t have a script file , Everything is done in a single bash shell — Jobs, Jan 18 '18 at 15:47
This is not the problem of evronmwng variable scope , if you assign y=“name=$NAME” , and then if you print y . You will get name=xyz as result — Jobs, Jan 18 '18 at 15:52

WEBjuju · Answer 1 · 2018-01-18T16:22:06.143

2

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

edited Jan 18 '18 at 16:22

answered Jan 18 '18 at 15:53

WEBjuju

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 05 '18 at 05:21

1 Answers1