su [OPTION]... [-] [USER [ARG]...]
Change the effective user id and group id to that of USER.
-, -l, --login
make the shell a login shell, clears all envvars except for
TERM, initializes HOME, SHELL, USER, LOGNAME and PATH
-c, --command=COMMAND
pass a single COMMAND to the shell with -c
--session-command=COMMAND
pass a single COMMAND to the shell with -c and do not create a
new session
-f, --fast
pass -f to the shell (for csh or tcsh)
-m, --preserve-environment
do not reset HOME, SHELL, USER, LOGNAME environment variables
-p same as -m
-s, --shell=SHELL
run SHELL if /etc/shells allows it
--help display this help and exit
--version
output version information and exit
A mere - implies -l. If USER not given, assume root.