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extern char ** _environ;
extern wchar_t ** _wenviron
_environ is an array of pointers to strings; it is used to access and alter the operating system environment variables. Each string is of the form:
envvar = varvalue
where envvar is the name of an environment variable (such as PATH), and varvalue is the string value to which envvar is set (such as C:\Utils;C:\MyPrograms). The string varvalue can be empty.
When a program begins execution, the operating system environment settings are passed directly to the program. Note that env, the third argument to main, is equal to the initial setting of _environ.
The _environ array can be accessed by getenv; however, the putenv function is the only routine that should be used to add, change or delete the _environ array entries. This is because modification can resize and relocate the process environment array, but _environ is automatically adjusted so that it always points to the array.
|POSIX||Win32||ANSI C||ANSI C++|