su(1)                                                       su(1)



     NAME
          su - substitute user ID

     SYNOPSIS
          su [-] [name[arg ...]]

     DESCRIPTION
          su allows a user to become another user without logging off.
          The default user name is root (that is, superuser).

          To use su, the appropriate password must be supplied (unless
          one is already root).  If the password is correct, su will
          execute a new shell with the real and effective user ID set
          to that of the specified user.  The new shell will be the
          optional program named in the shell field of the specified
          user's password file entry (see passwd(4)), or /bin/sh if
          none is specified (see sh(1)).  To restore normal user ID
          privileges, type an EOF (CONTROL-D) to the new shell.

          Any additional arguments given on the command line are
          passed to the program invoked as the shell.  When using pro-
          grams like sh(1), an arg of the form -c string executes
          string via the shell and an argument of -r will give the
          user a restricted shell.

          The following statements are true only if the optional pro-
          gram named in the shell field of the specified user's pass-
          word file entry is like sh(1).  If the first argument to su
          is a -, the environment will be changed to what would be ex-
          pected if the user actually logged in as the specified user.
          This is done by invoking the program used as the shell with
          an arg0 value whose first character is -, thus causing the
          system's profile (/etc/profile) and then the specified
          user's profile (.profile in the new HOME directory) to be
          executed.  Otherwise, the environment is passed along with
          the possible exception of $PATH, which is set to
          /bin:/etc:/usr/bin:/usr/etc for root.  Note that if the op-
          tional program used as the shell is /bin/sh, the user's
          .profile can check arg0 for -sh or -su to determine if it
          was invoked by login(1) or su(1), respectively.  If the
          user's program is other than /bin/sh, then the program is
          invoked with an arg0 of -program by both login(1) and su(1).

          All attempts to become another user using su are logged in
          the log file /usr/adm/sulog.

     EXAMPLES
          The command

             su trip

          would cause the system to prompt for trip's password; if the



     April, 1990                                                     1

     su(1)                                                       su(1)



          password is typed in correctly, trip's identity is substi-
          tuted.

          To become user bin while retaining the previously exported
          environment, execute

             su bin

          To become user bin but change the environment to what would
          be expected if bin had originally logged in, execute

             su - bin

          To execute command with the temporary environment and per-
          mission of user bin, type

             su - bin -c "command args"


     FILES
          /bin/su
          /etc/passwd
          /etc/profile
          $HOME.profile
          /usr/adm/sulog

     SEE ALSO
          csh(1), env(1), ksh(1), login(1), sh(1), passwd(4), pro-
          file(4), environ(5).


























     2                                                     April, 1990