Write the versions of the library functions strncpy, strncat, and strncmp, which operate on at most the first n characters of their argument strings. For e.g strncpy(s, t) copies at most n characters of t to s.

/*strncpy:copy n characters from t to s */
void strncpy(char *s, char *t, int n){
     while(*t && n-->0)
           *s++ = *t++;
     while(n-- > 0)
         *s++ = '\0';
}
/*strncat:concatenate n characters of t to the end of s */
void strncat(char *s, char *t, int n){
     void strncpy(char *s, char *t, int n);
     int strlen(char *t);

    strncpy(s + strlen(s), t, n);
}

/*strncmp ; compare at most n characters of t with s */
int strncmp(char *s, char *t, int n){
      for(; *s == *t; s++, t++)
        if (*s == '\0' || --n <= 0)
            return 0;
      return *s - *t;
}