2.14.8 strncat

Declaration:

char *strncat(char *str1, const char *str2, size_t n);

Appends the string pointed to by str2 to the end of the string pointed to by str1 up to n characters long. The terminating null character of str1 is overwritten. Copying stops once n characters are copied or the terminating null character of str2 is copied. A terminating null character is always appended to str1. If overlapping occurs, the result is undefined.

The argument str1 is returned.