cat -n

#!/bin/bash -e
typeset -i DIGIT=$(sed -n $= $1)
typeset -i digit
if (( DIGIT < 10 )); then digit=1
elif (( DIGIT < 100 )); then digit=2
elif (( DIGIT < 1000 )); then digit=3
elif (( DIGIT < 10000 )); then digit=4
elif (( DIGIT < 100000 )); then digit=5
else exit 9
fi
typeset -i line_no=1
while read; do
  printf "%0*d %s\n" ${digit} $(( line_no++ )) "${REPLY}"
done <$1