C/string.h/strncat

    
//Declaration:  char *strncat(char *str1, const char *str2,  size_t count); 
//Return:       returns *str1. 
  
  #include <stdio.h>
  #include <string.h>
  int main(void)
  {
    char s1[80], s2[80];
    unsigned int len;
    gets(s1);
    gets(s2);

    len = 79-strlen(s2);
    strncat(s2, s1, len);
    printf(s2);
    return 0;
  }
         
/*
2
1
12*/