Not quite sure why you want to do this with C, a shell script would probably be easier. That being said:
PHP Code:
#include <process.h>
int execvp(const char * file, char * const argv[]);
execvp requires two parameters, one being the name of the process image (in this case 'mv'), and an array of strings for the arguments.
Note that execvp replaces the current process with the image of 'mv'. If you want your program to continue running after you exec, you will need to fork() prior to the exec().
I just noticed that you were using execve, which has three parameters, the third being the path. execvp just uses the path from your environment.