using grep to output error messages in /var/log/messages and using a loop?

Billy_6052 · 12-14-2014, 04:21 AM

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?

unSpawn · 12-14-2014, 05:11 AM

Quote:

Originally Posted by Billy_6052

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

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

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?

Billy_6052 · 12-14-2014, 07:58 AM

hi

thanks for the reply! will check that out I didn't use multiwall as the command does not exist.

Billy_6052 · 12-14-2014, 10:28 AM

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

SAbhi · 12-14-2014, 11:01 AM

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.