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bashvariablesechosudo

How can a Bash variable be used in a string passed to Bash?

Let's say I've got the following here-document (which is used to enable hibernation in Ubuntu):

IFS= read -d '' text << "EOF"
[Re-enable hibernate by default in upower]
Identity=unix-user:*
Action=org.freedesktop.upower.hibernate
ResultActive=yes

[Re-enable hibernate by default in logind]
Identity=unix-user:*
Action=org.freedesktop.login1.hibernate
ResultActive=yes
EOF

I could store this text in a protected file in a way like the following:

echo "${text}" | sudo tee /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla

How could I do a similar operation using the Bash variable in a command string (that's using the redirect operator) passed to Bash running under root?

sudo bash -c 'echo "${text}" > /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla'

In the new instance of Bash, the variable obviously doesn't exist.

Solution

  • One option would be to pass the variable as an argument, like this:

    sudo bash -c 'printf "%s\n" "$0" > /path/to/output' "$text"