su --help

[user@localhost ~]$ su --help

Usage: su [OPTION]... [-] [USER [ARG]...]

Change the effective user id and group id to that of USER.

  -, -l, --login               make the shell a login shell

  -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 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.

Report bugs to <bug-coreutils@gnu.org>.

[user@localhost ~]$