How to compare Date in Shell script ?


There is no in built function to compare dates in shell script . So we need to convert every date to second value from 1970 using ( date +%s ) option
After that we can compare it

[sterin@stjacob-lap ~]$ date
Thu Sep 17 15:10:28 IST 2015
[sterin@stjacob-lap ~]$ date +%s
1442482830


Example :

Date format is : 16/Sep/2015:16:20:32 dd/Mmm/YYY:HH:MM:SS
Date 1 : 16/Sep/2015:16:20:32
Date 2 : Current System date

Script :

----------------------------------------------------------------------------------------------------
# #1 is input date to compare with system time

now=`date  +%s`




   dt1=`echo $1 | sed 's:/:-:g; s/:/ /'`

              t1=`date --date="$dt1" +%s`

                let "tDiff=$now-$t1"
                let "hDiff=$tDiff/3600"
                

                if [ $hDiff -lt 1 ]
                  then
                     echo " System Date is Eariler  "
                  else
                     echo " System Date is Later    "
                fi
---------------------------------------------------------------------------------------------------------

Output
[oracle@stjacob-pc1 tmp]$ ./datecompare.sh 16/Sep/2015:16:21:36
 System Date is Later   
[oracle@stjacob-pc1 tmp]$ ./datecompare.sh 20/Sep/2015:16:21:36
 System Date is Eariler