Sure, but just use execvp and it's a damn sight safer because you know exactly the state of your child's environment state. You can see this in the CERT C coding guidelines: https://wiki.sei.cmu.edu/confluence/display/c/ENV03-C.+Sanit...

also ENV02-C comes into effect, as well, if your program is invoked with

    SOME_INTERNAL_VARIABLE=1 PORT=2000 ./prog

then you try to invoke your child with:

    setenv("SOME_INTERNAL_VARIABLE", "2", 1);
    (fork blah blah)