If the invoked shell is csh(1), this option prevents it from reading the ".cshrc" file.
Simulate 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 "/bin:/usr/bin". TERM is imported from your current environment. Environment variables may be set or overridden from the login class capabilities database according to the class of the target login. The invoked shell is the target logins, and su will change directory to the target logins home directory. Resource limits and session priority are modified to that for the target accounts login class.
(no letter) The same as -l .
Leave the environment unmodified. The invoked shell is your login shell, and no directory changes are made. As a security precaution, if the target users shell is a non-standard shell (as defined by getusershell(3)) and the callers real uid is non-zero, su will fail.
Set the MAC label to the users default label as part of the user credential setup. Setting the MAC label may fail if the MAC label of the invoking process is not sufficient to transition to the users default MAC label. If the label cannot be set, su will fail.
Use the settings of the specified login class. Only allowed for the super-user.
The -l (or ) and -m options are mutually exclusive; the last one specified overrides any previous ones.
If the optional args are provided on the command line, they are passed to the login shell of the target login. Note that all command line arguments before the target login name are processed by su itself, everything after the target login name gets passed to the login shell.
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.
Runs the command catman as user man. You will be asked for mans password unless your real UID is 0.
"su man -c catman /usr/share/man /usr/local/man /usr/X11R6/man"
Same as above, but the target command consists of more than a single word and hence is quoted for use with the -c option being passed to the shell. (Most shells expect the argument to -c to be a single word).
"su -c staff man -c catman /usr/share/man /usr/local/man /usr/X11R6/man"
Same as above, but the target command is run with the resource limits of the login class "staff". Note: in this example, the first -c option applies to su while the second is an argument to the shell being invoked.