int_calc.sh

#!/bin/bash

echo expr
time ( for t in `seq 100`; do
  prod=1
  for i in `seq 1 10`; do
    prod=`expr $prod \\* $i`
  done
done ) 2>&1
echo

echo "\$(())"
time ( for t in `seq 100`; do
  prod=1
  for i in `seq 1 10`; do
    prod=$(( $prod * $i ))
  done
done ) 2>&1
echo

echo let
time ( for t in `seq 100`; do
  prod=1
  for i in `seq 1 10`; do
    let "prod = prod * i"
  done
done ) 2>&1
echo

echo bc
time ( for t in `seq 100`; do
  prod=1
  for i in `seq 1 10`; do
    prod=`echo $prod \\* $i | bc`
  done
done ) 2>&1
echo

cat << EOM
# result
expr

real    0m0.631s
user    0m0.040s
sys     0m0.638s

$(())

real    0m0.063s
user    0m0.001s
sys     0m0.067s

let

real    0m0.065s
user    0m0.012s
sys     0m0.057s

bc

real    0m1.010s
user    0m0.063s
sys     0m1.255s

EOM