Shell Programming and Scripting

I am trying to find the difference in days between 2 dates.
I have to extract the 1st date from a filename, which i did using the awk command.
I have to compare this date to today's date and if the difference is greater than 30 days, do something, else do something else.

This is what i wrote

Code:

INVDATE=`echo "SHIP_606400_2008233202_20080206_070308083544.xml"|awk -F_ '{print $4}'`
echo $INVDATE
TODAY=`date +"%Y%m%d"`
echo $TODAY
(( diff=$TODAY-$INVDATE))
echo $diff
if [ $diff -gt 30 ]; then
     #do a
else
  #do b
fi

The result that I got was

Code:

20080206
20080311
105

The difference between the dates is not 105 days, but 34 days.

What am i doing wrong - I am pretty new to Shell programming and am learning through this site.

Thanks in advance.

It's because it's subtracting one number from the other. The subtraction you're doing has no concept of dates.

There are many ways to go about this. What exactly are you trying to do?

A couple of possibilities:

A find command using the -mtime and -exec options (you can search for all files over 30 days old and do something to them).

A short script which returns the difference in days between a file's last-modified time and the current system time, to be embedded in your script.

As usual, providing as much information as possible will get you the best results. Also, try searching this site -- your question has probably been answered many times. It depends on exactly what you're trying to do.

ShawnMilo

Shawn,
Thanks for the quick response. This is what I am trying to do - these XML files are shipment files and these shipments need to be loaded into a database, dependent on some conditions.
This XML can be created any day(hence the last modified date is not an option), but it has to be loaded into the database only if the shipment is for within the last 30 days, otherwise it has to be archived to a different folder, without loading into the datatbase.
Is there any way to convert these numbers to date in UNIX (a very warped up way would be to connect to the database and do the calculation there - very unsophisticated)
Thanks again for your help.

Okay, I think I get it now. You have a directory with any number of XML files. You need to read them to find out the date (stored as text) from a certain position in a record in the XML file. Depending on whether that date falls within a certain range, you either want to process the file into your database, or move the whole XML file to another directory, where it will wait to be checked later.

Is that correct?

Can there be multiple orders per XML file? If so, what if there are different dates for the different orders?

Please post an example of the XML file (if it's small enough), or at least the line(s) with the date you are trying to check. If there are multiple lines in the XML file which do not have dates, explain how the program should figure out if a particular line should be checked or ignored.

ShawnMilo

This is a bit similar to an older post: https://www.unix.com/shell-programmin...two-dates.html

I would suggest convert both the dates to "epoch" seconds, then do a awk operation to convert the epoch diff secs to num days.

something like:

Code:

$ cat days.sh
D1=`echo "SHIP_606400_2008233202_20080206_070308083544.xml"|awk -F_ '{print $4}'`
E1=`date +%s -d"$D1"`
E2=`date +%s` #present time
((diff_sec=E2-E1))
echo - | awk -v SECS=$diff_sec '{printf "Number of days : %d",SECS/(60*60*24)}'

Code:

$ sh days.sh
Number of days : 35

//Jadu

Jadu -
That requires GNU date, so you should mention that not all UNIX boxes have it as what you show "exceeds" POSIX standards.

HI Shawn,
NO- the date is in the filename itself - SHIP_606400_2008233202_20080206_070308083544.xml - in this case "20080206".
Also, there is only 1 shipment per XML file for the date mentioned in the file name.

Thanks for your help. Is there any way to convert a string to a Julian date?