4.4BSD/usr/share/man/cat3/unsetenv.0

GETENV(3)                   BSD Programmer's Manual                  GETENV(3)

NNAAMMEE
     ggeetteennvv, ppuutteennvv, sseetteennvv, uunnsseetteennvv - environment variable functions

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<ssttddlliibb..hh>>

     _c_h_a_r _*
     ggeetteennvv(_c_o_n_s_t _c_h_a_r _*_n_a_m_e);

     _i_n_t
     sseetteennvv(_c_o_n_s_t _c_h_a_r _*_n_a_m_e, _c_o_n_s_t _c_h_a_r _*_v_a_l_u_e, _i_n_t _o_v_e_r_w_r_i_t_e);

     _i_n_t
     ppuutteennvv(_c_o_n_s_t _c_h_a_r _*_s_t_r_i_n_g);

     _v_o_i_d
     uunnsseetteennvv(_c_o_n_s_t _c_h_a_r _*_n_a_m_e);

DDEESSCCRRIIPPTTIIOONN
     These functions set, unset and fetch environment variables from the host
     _e_n_v_i_r_o_n_m_e_n_t _l_i_s_t. For compatibility with differing environment conven-
     tions, the given arguments _n_a_m_e and _v_a_l_u_e may be appended and prepended,
     respectively, with an equal sign ``=''.

     The ggeetteennvv() function obtains the current value of the environment vari-
     able, _n_a_m_e. If the variable _n_a_m_e is not in the current environment , a
     null pointer is returned.

     The sseetteennvv() function inserts or resets the environment variable _n_a_m_e in
     the current environment list.  If the variable _n_a_m_e does not exist in the
     list, it is inserted with the given _v_a_l_u_e_. If the variable does exist,
     the argument _o_v_e_r_w_r_i_t_e is tested; if _o_v_e_r_w_r_i_t_e _i_s zero, the variable is
     not reset, otherwise it is reset to the given _v_a_l_u_e.

     The ppuutteennvv() function takes an argument of the form ``name=value'' and is
     equivalent to:

           setenv(name, value, 1);

     The uunnsseetteennvv() function deletes all instances of the variable name point-
     ed to by _n_a_m_e from the list.

RREETTUURRNN VVAALLUUEESS
     The functions sseetteennvv() and ppuutteennvv() return zero if successful; otherwise
     the global variable _e_r_r_n_o is set to indicate the error and a -1 is re-
     turned.

EERRRROORRSS
     [ENOMEM]  The function sseetteennvv() or ppuutteennvv() failed because they were un-
               able to allocate memory for the environment.

SSEEEE AALLSSOO
     csh(1),  sh(1),  execve(2),  environ(7)

SSTTAANNDDAARRDDSS
     The ggeetteennvv() function conforms to ANSI C X3.159-1989 (``ANSI C '').

HHIISSTTOORRYY
     The functions sseetteennvv() and uunnsseetteennvv() appeared in Version 7 AT&T UNIX.
     The ppuutteennvv() function appeared in 4.3BSD-Reno.

4.4BSD                           June 4, 1993                                1