32v 1m su
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SU(1) UNIX Programmer's Manual SU(1)
su - substitute user id temporarily
su [ userid ]
_S_u demands the password of the specified _u_s_e_r_i_d, and if it is given, changes to that _u_s_e_r_i_d and invokes the Shell _s_h(1) without changing the current directory or the user environ- ment (see _e_n_v_i_r_o_n(5)). The new user ID stays in force until the Shell exits.
If no _u_s_e_r_i_d is specified, `root' is assumed. To remind the super-user of his responsibilities, the Shell substitutes `#' for its usual prompt.