[snip]
DESCRIPTION
The strcat() function appends a copy of the 
string pointed to by the s2 parameter (including
the terminating null byte) to the end of the string
pointed to by the s1 parameter.  The initial byte 
of s2 overwrites the null byte at the end of the 
string pointed to by s1.  When operating on overlapping
strings, the behavior of this function is unreliable.