mv'ing files from a C program

[Guy Harris]

>Both seem kind of expensive.  What's wrong with rename....  (man 2
>rename).

It's not present in all systems. 

It's present in (4.2andup)BSD-based systems, including System V Release
4.  (1/2 :-) - there are plenty of things from BSD in there....) It's
also specified by POSIX, so any POSIX-compliant system will have it.

It's not in vanilla S5R3 from AT&T (unless it snuck into S5R3.2 - some
vendors S5R3-based systems may have added it, but others may not have),
nor in any earlier AT&T releases.