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Old 12-14-2014, 05:21 AM   #1
Billy_6052
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Unhappy using grep to output error messages in /var/log/messages and using a loop?


hi

ive created a script where I want to grep out any error messages and colour the word 'error'. the script I have made so far is:

#!/bin/bash
cat /var/log/messages | grep --color=always "error" | tail

when I run the script there is no output.

also I want to use a loop so I am able to chose wheather I want to look in the /var/log/messages or /var/log/boot.log.... is that possible?
 
Old 12-14-2014, 06:11 AM   #2
unSpawn
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Quote:
Originally Posted by Billy_6052 View Post
ive created a script where I want to grep out any error messages and colour the word 'error'.
Luckily nobody has ever done this before! ;-p
Any particular reason not to use the (previously suggested) multitail, ctail or ccze?


Quote:
Originally Posted by Billy_6052 View Post
the script I have made so far is:
Code:
#!/bin/bash
cat /var/log/messages | grep --color=always "error" | tail
when I run the script there is no output.
Instead tail a file ('man tail') then grep for it:
Code:
tail -f /var/log/messages | grep --color=always "error"

Quote:
Originally Posted by Billy_6052 View Post
also I want to use a loop so I am able to chose wheather I want to look in the /var/log/messages or /var/log/boot.log.... is that possible?
Either select files by providing them as argument to your script, by using a selector with say "getopts" (in BASH shell: 'help getopts') or use "select" (in BASH shell: 'help select').


*Also note this about the 3rd or 4th thread on the same subject so please keep your topic in one place from now on, OK?
 
1 members found this post helpful.
Old 12-14-2014, 08:58 AM   #3
Billy_6052
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hi

thanks for the reply! will check that out I didn't use multiwall as the command does not exist.
 
Old 12-14-2014, 11:28 AM   #4
Billy_6052
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i tried what you said, putting the tail -f first, still no output.

also im confused with getopt. how would I select a file as an argument, I looked at the man page and help and I looked online and I cant understand it

Last edited by Billy_6052; 12-14-2014 at 11:33 AM.
 
Old 12-14-2014, 12:01 PM   #5
SAbhi
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if
Code:
tail -f /something/ | grep <somethingelse>
doesn't gives you expected
then there is no output for your search term at current.

to view last errors you may try using tail without -f option else giving a limit of -100 lines or using
Code:
 grep <somethingelse> filename
they can give you an output if there is any.. although i would not suggest using grep directly, the output could be huge depending upon the search term used.

Last edited by SAbhi; 12-14-2014 at 12:02 PM.
 
  


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