Provided by: login_4.1.4.2-1ubuntu3_i386 bug

su - ID .SH

       su  [-flmp]  [-c   [-s  ]  [--login]  [--fast] [--preserve-environment]
       [--command= [--shell=] [-] [--help] [--version] [ [...]]

 GNU
       su

       su

         ID,  ID, USER USER    root
         USER     /bin/sh USER su
          ID 0 ()

       , su
           USER   `HOME', `SHELL'     `USER' `LOGNAME' USER

       su
        /bin/sh (argv[0]"-su"  -c     ... )

       syslog  , su
         , su
        syslog

       -c COMMAND, --command=COMMAND

              -c

       -f, --fast

              -f

              csh

              tcsh
                , -f
                .cshrc) -f

       --help

       -, -l, --login
                   `TERM', `HOME', `SHELL' ( )  `USER', `LOGNAME'(
                   `PATH'
                USER      "-"

       -m, -p, --preserve-environment
              `HOME', `USER', `LOGNAME', `SHELL'

              su

              /etc/passwd  USER `SHELL'

                /etc/shells   /etc/shells

              --login --shell

       -s, --shell shell
              su

              /etc/passwd  USER

       --version