BASH for loop

# Output 1 2 3...99
for i in {1..99}
do
   echo $i
done

for ((i=1;i<=99;i++))
do
   echo $i
done

for i in `seq 1 99`
do
   echo $i
done

# Output 1 3 5...99
for i in `seq 1 2 99`
do
   echo $i
done

# Output a to z
for i in {a..z}
do
   echo $i
done