スペース区切りで変数を分解するベンチマーク.

bash-split-variables-benchmark.sh

#!/bin/bash
set -ue
NUM_LOOPS=1000

use_cut(){
  for i in $(seq 1 $NUM_LOOPS)
  do
    line="i-ec56a9f5 vol-07d00601 servername"
    instance_id=`echo $line | cut -d' ' -f1`
    volome_id=`echo $line | cut -d' ' -f2`
    instance_name=`echo $line | cut -d' ' -f3`
    echo $instance_id
    echo $volome_id
    echo $instance_name
  done
}

use_set(){
  for i in $(seq 1 $NUM_LOOPS)
  do
    line="i-ec56a9f5 vol-07d00601 servername"
    set -- $line
    instance_id=$1
    volome_id=$2
    instance_name=$3
    echo $instance_id
    echo $volome_id
    echo $instance_name
  done
}

use_herestring(){
  for i in $(seq 1 $NUM_LOOPS)
  do
    line="i-ec56a9f5 vol-07d00601 servername"
    read instance_id volome_id instance_name <<< "$line"
    echo $instance_id
    echo $volome_id
    echo $instance_name
  done
}

use_array(){
  for i in $(seq 1 $NUM_LOOPS)
  do
    line="i-ec56a9f5 vol-07d00601 servername"
    instance_array=($line)
    instance_id=${instance_array[0]}
    volome_id=${instance_array[1]}
    instance_name=${instance_array[2]}
    echo $instance_id
    echo $volome_id
    echo $instance_name
  done
}

use_expansion(){
  for i in $(seq 1 $NUM_LOOPS)
  do
    line="i-ec56a9f5 vol-07d00601 servername"
    instance_id=${line%% *}
    rest_fields=${line% *}
    volome_id=${rest_fields#* }
    instance_name=${rest_fields##* }
    echo $instance_id
    echo $volome_id
    echo $instance_name
  done
}

echo "cut version" >&2
time use_cut
echo "" >&2
echo "set version" >&2
time use_set
echo "" >&2
echo "herestring version" >&2
time use_herestring
echo "" >&2
echo "bash array version" >&2
time use_array
echo "" >&2
echo "bash parameter expansion version" >&2
time use_expansion

実行結果

$ bash benchmark.sh > /dev/null
cut version

real    0m12.197s
user    0m4.914s
sys 0m8.414s

set version

real    0m0.099s
user    0m0.093s
sys 0m0.005s

herestring version

real    0m0.413s
user    0m0.143s
sys 0m0.261s

bash array version

real    0m0.120s
user    0m0.113s
sys 0m0.007s

bash parameter expansion version

real    0m0.134s
user    0m0.126s
sys 0m0.007s