strcat - concatenate strings
Standard C Library (libc, -lc)
#include <string.h>
char *
strcat(char *dest,
const char *src);
strcat appends the contents of the string src to the string dest.
If dest does not point to enough space to hold both strings, the resulting behavior is undefined.
If the memory areas pointed to by dest and src overlap, the behavior is undefined.
strcat returns dest.