UNSETENV(3)                POSIX Programmer's Manual               UNSETENV(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       unsetenv -- remove an environment variable

SSYYNNOOPPSSIISS
       #include <stdlib.h>

       int unsetenv(const char *_n_a_m_e);

DDEESSCCRRIIPPTTIIOONN
       The _u_n_s_e_t_e_n_v() function shall remove an environment variable from the
       environment of the calling process. The _n_a_m_e argument points to a
       string, which is the name of the variable to be removed. The named
       argument shall not contain an ''=='' character. If the named variable does
       not exist in the current environment, the environment shall be
       unchanged and the function is considered to have completed
       successfully.

       The _u_n_s_e_t_e_n_v() function shall update the list of pointers to which
       _e_n_v_i_r_o_n points.

       The _u_n_s_e_t_e_n_v() function need not be thread-safe.

RREETTUURRNN VVAALLUUEE
       Upon successful completion, zero shall be returned. Otherwise, -1 shall
       be returned, _e_r_r_n_o set to indicate the error, and the environment shall
       be unchanged.

EERRRROORRSS
       The _u_n_s_e_t_e_n_v() function shall fail if:

       EEIINNVVAALL The _n_a_m_e argument points to an empty string, or points to a
              string containing an ''=='' character.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       Refer to the RATIONALE section in _s_e_t_e_n_v().

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _g_e_t_e_n_v(), _s_e_t_e_n_v()

       The Base Definitions volume of POSIX.1-2017, <<ssttddlliibb..hh>>, <<ssyyss__ttyyppeess..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                          UNSETENV(3)
