Huh - I remember using `char env` as the third parameter to main. After a quick Googling, it would seem that's a GCC-specific thing. Surprised there's a Linux-specific (or ELF-specific, as another commented) convention other than that one.
It isn't specific to GCC at all. It's widespread among unixes historically (and they generally have their own C compiler which is not GCC), and it was mentioned in the C89 standard.
However, it is not part of standard C or POSIX/SUS.
