* returns ptr to value associated with name, if any, else NULL
register char **p
= environ
;
if ((v
= nvmatch(name
, *p
++)) != NULL
)
* s1 is either name, or name=value
* if names match, return value of s2, else NULL
* used for environment searching: see getenv
if (*s1
== '\0' && *(s2
-1) == '=')