www.pudn.com > FP-GROWTH.rar > tid2set

#!/bin/sh
gawk '
function output ()
{
  if (i > 0)
    printf("%s",  items[0]);
  for (k = 0; ++k < i; )
    printf(" %s", items[k]);
  printf("\n");
}

BEGIN { tid = ""; i = 0; }
{
  if ($1 == tid)
    items[i++] = $2;
  else {
    if (tid != "") output();
    tid      = $1;
    items[0] = $2; i = 1;
  }
}
END { output(); }
' $1 > $2