Copyright (c) 1988 The Regents of the University of California.
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@(#)su.1 6.7 (Berkeley) 12/07/88

C su - substitute user id su [-flm] [login] Su requests the password for login (or for ``root'', if no login is provided), and switches to that user and group ID. A shell is then invoked.

By default, your environment is unmodified with the exception of USER, HOME, and SHELL. HOME and SHELL are set to the target login's /etc/passwd values. USER is set to the target login, unless the target login has a UID of 0, in which case it is unmodified. The invoked shell is the target login's. This is the traditional behavior of su.

The -l option simulates a full login. The environment is discarded except for HOME, SHELL, PATH, TERM, and USER. HOME and SHELL are modified as above. USER is set to the target login. PATH is set to ``/usr/ucb:/bin:/usr/bin''. TERM is imported from your current environment. The invoked shell is the target login's, and su will change directory to the target login's home directory.

The -m option causes the environment to remain unmodified, and the invoked shell to be your login shell. No directory changes are made. As a security precaution, if the -m option is specified, the target user's shell is a non-standard shell (as defined by getusershell(3)) and the caller's real uid is non-zero, su will fail.

If the invoked shell is csh, the -f option prevents it from reading the .cshrc file. Otherwise, this option is ignored.

Only users in group 0 (normally ``wheel'') can su to ``root''.

By default (unless the prompt is reset by a startup file) the super-user prompt is set to ``#'' to remind one of its awesome power.

csh(1), login(1), sh(1), passwd(5), group(5), environ(7)