Using "grep" within a CRON Job

QuestionMqrk · 10-24-2016, 04:07 AM

Hi everyone;

Recently I set up a little CRON job that saves logs of the SmartCTL results.

Code:

>0 11 * * * /usr/sbin/smartctl -aixcA -d sat /dev/sda > /home/user_name_censored/CRON/smartctl-output-$(/bin/date +\%d\%m\%y)

Now i'm looking to make it save only a certain part of the Smart results; preferably just the Attribute List to show if the drive would fail soon.

I've been told to try "grep" to search for patterns in the text file but am having trouble understanding how to use it. Any guides online are either too complicated for me to understand or not exactly what i'm looking for. Any help would be greatly appreciated.

TenTenths · 10-24-2016, 04:27 AM

Code:

grep PATTERN [FILE]

So... and these are on the command line, not through any cron job:

Code:

# smartctl -a /dev/sda
smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.10.0+2] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

Vendor:               LSI
Product:              MR9271-4i
Revision:             3.45
User Capacity:        3,999,688,294,400 bytes [3.99 TB]
Logical block size:   512 bytes
Logical Unit id:      0x600605b00b6d7d501eeb815b5ba29659
Serial number:        005996a25b5b81eb1e507d6d0bb00506
Device type:          disk
Local Time is:        Mon Oct 24 11:11:22 2016 CEST
Device does not support SMART

Error Counter logging not supported
Device does not support Self Test logging

But if I only want the "Serial number"

Code:

# smartctl -a /dev/sda | grep "Serial number"
Serial number:        005996a25b5b81eb1e507d6d0bb00506

There are more advanced ways to specify patterns, for example to get the capacity and serial:

Code:

# smartctl -a /dev/sda | grep "Serial\|Capacity"
User Capacity:        3,999,688,294,400 bytes [3.99 TB]
Serial number:        005996a25b5b81eb1e507d6d0bb00506

You'll also see that grep checks the lines in order and if they match the pattern they'll be displayed, regardless of the order in the pattern.

You're also now at the stage where your cron line is getting a bit complicated so you might want to consider creating a shell script and calling that from cron.

QuestionMqrk · 10-24-2016, 05:34 AM

So, thanks to your brief explanation, I came up with this:

Code:

0 11 * * * /usr/sbin/smartctl -aixcA -d sat /dev/sda | grep -w "Reallocated_Sector_Ct\|Spin_Retry_Count\|Reallocated_Event_Count\|Current_Pending_Sector\|Offline_Uncorrectable > /home/user_name_censored/CRON/smartctl-output-$(/bin/date +\%d\%m\%y)

Basically pulling all the infos I need from Smart and putting into a file. I've given it a test run and it works seamlessly. Your examples of having grep filter out multiple items was particularly helpful. Thank you!

QuestionMqrk · 10-24-2016, 05:40 AM

A small follow-up question - how can I get it to, rather than create a new file each time it runs, edit one file by adding the date, followed by the results, to the top (or bottom, if it's too complicated to have the most recent first) of the file?

So for now the command I posted above creates a file for each log; but I'd prefer to have everything in one place.

So it can be:

24.10.16

5 Reallocated_Sector_Ct PO--CK 200 200 140 - 0
10 Spin_Retry_Count -O--C- 100 100 051 - 0
196 Reallocated_Event_Count -O--CK 200 200 000 - 0
197 Current_Pending_Sector -O--C- 199 198 000 - 35
198 Offline_Uncorrectable ----C- 200 200 000 - 0

25.10.16

5 Reallocated_Sector_Ct PO--CK 200 200 140 - 0
10 Spin_Retry_Count -O--C- 100 100 051 - 0
196 Reallocated_Event_Count -O--CK 200 200 000 - 0
197 Current_Pending_Sector -O--C- 199 198 000 - 35
198 Offline_Uncorrectable ----C- 200 200 000 - 0

...and so forth.

TenTenths · 10-24-2016, 06:03 AM

Now you really should be looking at turning this in to a script as it's going to start to get really unreadable on a single line:

Code:

0 11 * * * /bin/date >> /home/user_name_censored/CRON/smartctl-output && /usr/sbin/smartctl -aixcA -d sat /dev/sda | /bin/grep -w "Reallocated_Sector_Ct\|Spin_Retry_Count\|Reallocated_Event_Count\|Current_Pending_Sector\|Offline_Uncorrectable" >>  /home/user_name_censored/CRON/smartctl-output

Note that this will append results to the file /home/user_name_censored/CRON/smartctl-output and the date output will be the full date format.

QuestionMqrk · 10-24-2016, 07:52 AM

This is exactly what I meant. Thanks for the help.

Regarding creating a script; it will only be running for about a month and I won't be using this computer for anything else Terminal-Related so I think it's fine. Cheers though.