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Accepted
Jonathan
Asked: 2017-01-01 11:08:54 +0800 CST

Can I access the originating $USER variable from within a script run with `sudo`?

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A weird question, I know. Here's the script: 

echo $USER

Here's the command I use to run it: 

sudo ./myscript.sh

Right now it prints "root" but I want it to print jon, my username. Is there a way to do that by changing the script, and not the command?

command-line

2 Answers

  1. Best Answer

    Use the SUDO_USER environment variable instead of USER.

    sudo places the name of the user who ran it in the SUDO_USER environment variable:

    ek@Io:~$ sudo sh -c 'echo $USER'
[sudo] password for ek:
root
ek@Io:~$ sudo sh -c 'echo $SUDO_USER'
ek

    So you can simply replace $USER with $SUDO_USER in your script:

    echo $SUDO_USER

    Further Reading

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  2. In addition to @Eliah Kagan's answer above, I would like to point out that you can also easily have an expansion which works both if it runs in a sudo context or not:

    echo "${SUDO_USER:-$USER}"

    This expands to the value of $SUDO_USER by default, but if if that variable is unset or empty, it falls back to the value of $USER. 

    $ bash -c 'echo "${SUDO_USER:-$USER}"'
bytecommander

$ sudo bash -c 'echo "${SUDO_USER:-$USER}"'
bytecommander

    More information about default parameter expansion in Bash can be found e.g. on https://wiki.bash-hackers.org/syntax/pe#use_a_default_value.

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