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bashgnu-screen

Using environment variables in commands passed to screen

To execute a command in a detached screen I can do this (after creating a screen, screen -dmS myscreen bash):

screen -S myscreen -X stuff $'echo hello\n'

However this syntax messes with $ for environment variables:

MSG="hello"
screen -S myscreen -X stuff $'echo $MSG\n' #doesn't work

What can I do instead?

Solution

  • Use a double-quoted string for the part that needs to expand a variable, and a dollar-quoted string for the part that contains the escape sequence, and concatenate them.

    screen -S myscreen -X stuff "echo $MSG"$'\n'

    Another option is to assign the newline string to a variable:

    NL=$'\n'
screen -S myscreen -X stuff "echo $MSG$NL"

    BTW, MSG is not an environment variable, it's just a shell variable. It doesn't become an environment variable unless you export it.