strcpy and strcat {C}

https://man7.org/linux/man-pages/man3/strcpy.3.html

strcpy()
      These functions copy the string pointed to by src, into a
      string at the buffer pointed to by dst.  The programmer is
      responsible for allocating a destination buffer large
      enough, that is, strlen(src) + 1.  For the difference
      between the two functions, see RETURN VALUE.

strcat()
      This function catenates the string pointed to by src,
      after the string pointed to by dst (overwriting its
      terminating null byte).  The programmer is responsible for
      allocating a destination buffer large enough, that is,
      strlen(dst) + strlen(src) + 1.