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Say I'm running bash as root, and I want to chown the home directory of a user ada. Say also that ada is stored in a variable called $USER (because I'm doing this from a script).

When I tried the following, 

chown -R $USER:$USER ~$USER

the shell performed tilde expansion first, so it tried to chown /home/root/ada, rather than /home/ada.

Is there some way to do it with nested substitions and proper escaping?

Chris Middleton
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2 Answers2

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Tilde expansion is tricky and doesn't work with variables like that.

One way is to use eval:

chown -R $USER:$USER $(eval echo ~"$USER")

But make sure your USER variable is not coming from untrusted sources.

anubhava
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I wound up here because I had the sort of problem.

I came up with:

chown -R $USER:$USER $(getent passwd $USER | awk -F: '{print $6}')

But I like anubhava's (slightly scary) eval based suggestion better.

Thanks!

chrismarget
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