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What's wrong with my "grep"

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Top Forums Shell Programming and Scripting What's wrong with my "grep"
# 1  
Old 07-14-2010
What's wrong with my "grep"
So I want dmesg to show out put only from today's date.

I figured this out...........
Code:
root@someserver:/# echo `date` | cut -f2-3 -d " "
Jul 14

Then why does this not work.
Code:
root@someserver:/# dmesg | grep "`date` | cut -f2-3 -d " ""

How can I make grep to evaluate the output of date command, I am sure I am missing something basic.
# 2  
Old 07-14-2010
1. the date command has format specifiers
Code:
var=date "+%b %d"

Read about the %b and %d in the date man page
2.
Code:
 
dmesg | grep -F "$var"

-F means look for a literal text pattern.

your construction needed:
$(date | awk '{print $2 $3}' )
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Tirmazi
# 3  
Old 07-14-2010
I think that the concept is flawed. On my system "dmesg" puts today's date in the heading and then outputs any system messages - even if they happened months ago. The messages themselves are rarely dated.
It is more relevant to look at the log from "syslogd" (the name and location of which depends on the Operating System).

What does your dmesg output look like?
This User Gave Thanks to methyl For This Post:
Tirmazi
# 4  
Old 07-14-2010
On solaris 8 the output for today's date is
Code:
root@stagingorcz1:/# dmesg | grep  "Jul 14" | grep -v sendmail
Wed Jul 14 16:35:47 CEST 2010
Jul 14 16:05:43  xntpd[1072]: [ID 774427 daemon.notice] time reset (step) 0.239301 s
Jul 14 16:05:43  xntpd[1072]: [ID 204180 daemon.info] synchronisation lost
Jul 14 16:11:02  xntpd[1072]: [ID 854739 daemon.info] synchronized to 217.147.223.78, stratum=2

so my point is it does sort by date.

---------- Post updated at 10:40 AM ---------- Previous update was at 10:37 AM ----------

My intention was not to make it complicated or to pass the value of $var to grep and use it in a scipt, I just wanted to run it on the command line, how would I do that?
# 5  
Old 07-14-2010
Code:
var=date "+%b %d"; dmesg | grep -F "$var"
# is the same as:
dmesg | grep -F $(date "+%b %d"  )
# the first one is easier for a beginning scripter to get it right

This User Gave Thanks to jim mcnamara For This Post:
Tirmazi
# 6  
Old 07-14-2010
I donot want to be annoying but I am sorry it didn't work on my Solaris 8 using bash
Code:
root@someserver/# dmesg | grep -F $(date "+%b %d"  )
grep: illegal option -- F
Usage: grep -hblcnsviw pattern file . . .
Broken Pipe
Broken Pipe

# 7  
Old 07-14-2010
About the shell problem.
Note the "%e" for the day of the week because syslogd date stamps don't have the leading zero on the day.

Code:
DDDMM=`date +"%b %e"`
dmesg|grep "${DDDMM}"


About the concept:
The output from "dmesg" is a limited buffer of messages sent to the system console. It is of little or no use for application monitoring.
In your example the syslog daemon has forwarded some messages to console. I would expect them to appear in one of the main system logs too but if they don't this is a syslog configuration problem.

You can get all sorts of messages from "dmesg" - try the command just after a reboot!
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