strncat.c\string\src - musl - musl - an implementation of the standard library for Linux-based systems

#include <string.h>
char *strncat(char *d, const char *s, size_t n)
{
	char *a = d;
	d += strlen(d);
	while (n && (*d++ = *s++)) n--;
	*d++ = 0;
	return a;
}