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bashenvsubst

Replace value of an environment variable declared in a file

There is a file env.sh, which defines environment variables:

$cat env.sh
export var1=1
export var2=2

I want to replace the value of var1 inside of the file with 3, so that 

$cat env.sh
export var1=3
export var2=2

Is there way to do it without string/regexp matching magic?

I read a lot about envsubst, but still was not able to figure out how to apply it to the task.

Solution

  • Just use a scriptable editor like ed:

    $ cat env.sh
export var1=1
export var2=2
$ printf  '/var1=/s/=.*/var1=3/\nw\n' | ed env.sh
28
28
$ cat env.sh
export var1=3
export var2=2