strcat, strncat – concatenate strings
Standard C Library (libc, -lc)
#include <string.h> char * strcat(char *restrict s1, const char *restrict s2); char * strncat(char *restrict s1, const char *restrict s2, size_t n);
YOU SHOULD ALMOST CERTAINLY USE strlcat() INSTEAD.
The strcat() and strncat() functions append a copy of the null-terminated string s2 to the end of the null-terminated string s1, then add a terminating '\0'.