Shell Programming and Scripting

#!/bin/sh
for a in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
 for b in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
  for c in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
   for d in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
    echo $a$b$c$d
   done
  done
 done
done

for ((i=1; i<=65535; i++)); do 
  printf "%04X\n" "$i"
done

i=0
while [ $i -le 65534 ] ; do 
  printf "%04X\n" "$((i+=1))"
done

for i in {1..65535}
do
   echo "obase=16;ibase=10;$i" | bc
done

{ echo obase=16;ibase=10
  for i in {1..65535}; do
    echo $i
  done
} | bc

"$((i+=1))"