------------------------------------------------- permut.awk -----------------------
# Give the parameter on STDIN like this:
# echo 4 | awk -f permut.awk

function freespot(ind) {
   if(ind >= 0){
      f[ind] = 1;
      if(ind < minfree){
         minfree = ind;
      }
   }
}
function takespot(ind,i) {
   if(ind >= 0){
      f[ind] = 0;
      if(ind == minfree){
         i = 0;
         for(i = minfree+1; i < num; ++i){
            if(f[i] == 1){
               minfree = i;
               break;
            }
         }
      }
   }
}
function perm () {
   count = 1;
   while(ind >= 0){
      start = c[ind]+1;
      if(start == 0){
         start = minfree;
      }
      i = start;
      for(i; i < num; ++i){
         if(f[i] == 1){
            freespot(c[ind]);
            takespot(i);
            c[ind] = i;
            if(ind < num-1){
               ind++;
            }else{
               freespot(i);
               j = 0;
               if(num > 100){
                  for(j = 0; j < 10; ++j){
                     printf("%i ", c[j]);
                  }
                  printf("... ");
                  for(j = num-10; j < num; ++j){
                     printf("%i ", c[j]);
                  }
               }else{
                  for(j = 0; j < num; ++j){
                     printf("%i ", c[j]);
                  }
               }
               printf("| %i\n", count);
               count++;
            }
            break;
         }
      }
      if(ind == old){
         freespot(c[ind]);
         c[ind] = -1;
         ind--;
      }
      old = ind;
   } 
}
{
   if($1 ~ /^[0-9]+$/){
      num = $1;
   }else{
      num = 2;
   }
   if(num < 2){
      num = 2
   }
   ind = 0;
   old = 0;
   minfree = 0;
   for(i = 0; i < num; ++i){
      c[i] = -1;
      f[i] = 1;
   }
   perm();
}