To invoke a login shell using
sudo just use
-i. When command is not specified you'll get a login shell prompt, otherwise you'll get the output of your command.
Example (login shell):
Example (with a specified user):
sudo -i -u user
Example (with a command):
sudo -i -u user whoami
Example (print user's
sudo -i -u user echo \$HOME
Note: The backslash character ensures that the dollar sign reaches the target user's shell and is not interpreted in the calling user's shell.
I have just checked the last example with strace which tells you exactly what's happening. The output bellow shows that the shell is being called with
--login and with the specified command, just as in your explicit call to bash, but in addition sudo can do its own work like setting the
# strace -f -e process sudo -S -i -u user echo \$HOME
execve("/usr/bin/sudo", ["sudo", "-S", "-i", "-u", "user", "echo", "$HOME"], [/* 42 vars */]) = 0
[pid 12270] execve("/bin/bash", ["-bash", "--login", "-c", "echo \\$HOME"], [/* 16 vars */]) = 0
I noticed that you are using
-S and I don't think it is generally a good technique. If you want to run commands as a different user without performing authentication from the keyboard, you might want to use SSH instead. It works for
localhost as well as for other hosts and provides public key authentication that works without any interactive input.
ssh user@localhost echo \$HOME
Note: You don't need any special options with SSH as the SSH server always creates a login shell to be accessed by the SSH client.