_setenv function???

[Doug Morris]

Just a question to some who may know.  
Recently trying to install some mail frontends on a SUN 3 I ran into the 
function setenv().  Where the code was trying to set an environment variable
for the process.  Now most unix types are familar with this functionality 
from the cshell and it does make sense that you could do the same from within
a program.  However,  I cannot seem to make Sun C recognize this!  I cannot
find the appropriate library reference to link in the function.  
Does anyone have an idea where this function may be found?

Thanks for any help.

Doug Morris
University of Illinois
Biomedical Magnetic Resonance Lab
Urbana Illinois 61801
dmorris at aries.scs.uiuc.edu