1日毎に交互に2つ処理を実行する|do two commands day by day

• 現在日時を1970年からの日数に変換し、その数が偶数、奇数で処理を振り分ける|calculate days from 1970. when the days is even, do one command and when the days is odd, do another command.

#!/bin/sh                                                                                    
set -u

A=`date +%s`
echo $A is seconds from 1970-01-01 00:00:00 UTC .

((B=$A/(24*60*60)))
echo $B is days from 1970-01-01 00:00:00 UTC .

((C=$B%2))
if [ $C -eq 0 ] 
then
  echo 'even'
  # write a command
else
  echo 'odd'
  # write another command
fi