Tcl_PutEnv - procedures to manipulate the environment

       const char *assignment (in)          Info  about  environment  variable  in the format “NAME=value”.  The
                                            assignment argument is in the system encoding.
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Tcl_PutEnv sets an environment variable. The information is  passed  in  a  single  string  of  the  form
       “NAME=value”.  This procedure is intended to be a stand-in for the UNIX putenv system call. All Tcl-based
       applications  using  putenv  should redefine it to Tcl_PutEnv so that they will interface properly to the
       Tcl runtime.

       environment, variable

Tcl                                                    7.5                                      Tcl_PutEnv(3tcl)

       Tcl_PutEnv - procedures to manipulate the environment

env(3tcl)

#include<tcl.h>

       int
       Tcl_PutEnv(assignment)