SYNOPSIS

     #include <stdlib.h>

     char *
     getenv(const char *name);

     int
     setenv(const char *name, const char *value, int overwrite);

     int
     putenv(const char *string);

     void
     unsetenv(const char *name);

DESCRIPTION

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

     The getenv() function obtains the current value of the environment vari-
     able, name.

     The setenv() function inserts or resets the environment variable name in
     the current environment list.  If the variable name does not exist in the
     list, it is inserted with the given value.  If the variable does exist,
     the argument overwrite is tested; if overwrite is zero, the variable is
     not reset, otherwise it is reset to the given value.

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

           setenv(name, value, 1);

     The unsetenv() function deletes all instances of the variable name
     pointed to by name from the list.

RETURN VALUES

     The getenv() function returns the value of the environment variable as a
     NUL-terminated string.  If the variable name is not in the current envi-
     ronment, NULL is returned.

     The setenv() and putenv() functions return the value 0 if successful;
     otherwise the value -1 is returned and the global variable errno is set
     to indicate the error.

ERRORS

     [ENOMEM]           The function setenv() or putenv() failed because they
                        were unable to allocate memory for the environment.

HISTORY

     The functions setenv() and unsetenv() appeared in Version 7 AT&T UNIX.
     The putenv() function appeared in 4.3BSD-Reno.

BSD                            December 11, 1993                           BSD