Help with Bash (grep/awk/etc)

piercey · 02-26-2008, 11:28 AM

Hey everyone,

I want to write a script which can parse data I get from a java tool. Basically the tool prints out a number of lines, but I'm only interested in the last line, which basically gives the status of a server. I'd like to parse this but I'm not certain what tools I should use.

Take the following example output of the tool:

Code:

./status.sh SERVER1
... lots of junk ...
00I: The server "SERVER1" is STARTED

./status.sh SERVER1
... lots of junk ...
00I: The server "SERVER1" is STARTING

./status.sh SERVER1
... lots of junk ...
09I: The server "SERVER1" cannot be reached. It appears to be stopped.

What I'd like to do, is to be able to operate based on the data returned from the "status.sh" script. If someone could recommend what tools would be best for this job I'd really appreciate it (grep -E ? awk?). I don't need any source code (although pseudo code would be welcome

).

Cheers,

ilikejam · 02-26-2008, 11:31 AM

Hi.

'tail -n 1' will give just the last line. You can grep from there I'd imagine, like:

Code:

if ./status.sh SERVER1 | tail -n1 | grep "cannot be reached"
    then
    echo "Noooooooooooooooooooooooooo."
fi

Dave

piercey · 02-26-2008, 11:45 AM

Hi, that was quick

I probably should of said I don't really have an issue with getting the last line, its more a case of getting the status itself that's confusing me. Since I need to check for the different kinds of status.

Some pseudo code of what I'm trying to do would look like this:

Code:

populate a variable "STATUS" from status.sh

case $STATUS in
STARTED)
 echo "...";;
STOPPED)
 echo "...";;
STARTING)
 echo "...";;
esac

The problem I have is with populating that STATUS variable. Perhaps it's just the way I'm thinking about it that's confusing me and this can be solved in an easier way.

Thanks again,

osor · 02-26-2008, 12:38 PM

Quote:

Originally Posted by piercey

The problem I have is with populating that STATUS variable. Perhaps it's just the way I'm thinking about it that's confusing me and this can be solved in an easier way.

So the format is always the same (the status is any text after ‘is’ on the last line)? In that case, what about the following:

Code:

STATUS=$( ./status.sh SERVER1 | sed -ne '${s/^.*is //;p}' )

slakmagik · 02-26-2008, 12:40 PM

If you mean you want the last word in a given line, you can get it with cut, which should be faster than awk. Grep only handles lines, so that wouldn't be what you want.

:echo '00I: The server "SERVER1" is STARTING' | cut -d' ' -f6
STARTING

If you want to perform an action based on status, you may be able to use the exit status.

:if ls nodir 2>/dev/null; then echo exists; else echo noexist; fi
noexist

You can also capture the specific code with $?.

If none of this helps, maybe restate the problem more precisely.

piercey · 02-26-2008, 01:52 PM

Thanks for the replies guys.

osor/digiot: Both methods work fine. Only slight problem is that for the server when it's stopped the last word is "stopped.". Not exactly a significant problem, just feels a little hackish (case's would be "STARTED", "STARTING" and "stopped.")

I'm really just doing this as a learning experience so I'm not in any rush to get this completed. I'm more interested in ways to solve it.

Quote:

If you want to perform an action based on status, you may be able to use the exit status.

This could be worthwhile. The problem is status.sh basically just sets some environment variables and runs a java application, I've no idea if it will respect exit status', so I didn't even try. I'll be sure to try it tomorrow when I'm at the machine again.

Cheers

chrism01 · 02-26-2008, 05:29 PM

Well, you could check for eack keyword (assuming each always appears on it's own)

Code:

result=`./status.sh|tail -1`
echo $result|grep stopped >dev/null
if [[ $? -eq 0 ]]
then
    echo "Server STOPPED"
fi
echo $result|grep START >dev/null
if [[ $? -eq 0 ]]
then
    echo "Server STARTED/ING"
fi

ghostdog74 · 02-26-2008, 06:56 PM

Code:

./status.h SERVER1 | awk 'END{
 pattern="STARTED|STARTING|STOPPED"
 if ( $0 ~ pattern) {
   print $0
 }
}'

slakmagik · 02-26-2008, 11:46 PM

Nice.

He said 'stopped' was lowercase though and he only wanted the last word, so maybe

Code:

 if (toupper($0) ~ pattern) {
   print $NF

piercey · 02-27-2008, 06:01 AM

Thanks for the replies guys

I tried getting the exit status of the status.sh script, but unfortunately it always returned a successful "0".

ghostdog74/digiot:
That script works fine (using toupper()), and so far I have the following;

Code:

STATUS=""

# Get Server Status
get_server_status() 
{ 
 # grab the status of the server
 STATUS=`./serverStatus.sh $SERVER | awk 'END{
  pattern="STARTED|STARTING|STOPPED"

  if ( toupper($0) ~ pattern) {
    print toupper($NF)
  }
 }'`

 case $STATUS in
  STARTED)
   echo "Server \"$SERVER\" is Started";;
  STARTING)
   echo "Server \"$SERVER\" is Starting";;
  STOPPED.)
   echo "Server \"$SERVER\" is Stopped";;
  *)
   echo "Status Unknown for \"$SERVER\"";;
 esac
}

SERVER=Server1
get_server_status

SERVER=Server2
get_server_status

How does this look? Any suggestions for improvements? I'm not very familiar with bash coding etiquette so if there's a better way to do it I'm interested to hear

Cheers,

ghostdog74 · 02-27-2008, 07:17 AM

good effort. When you are better at scripting as you go along, you can do everything (almost) in awk.
Just for the fun of it

Code:

./status.sh | awk -v server=$SERVER 'END{
  pattern="STARTED|STARTING|STOPPED"
  status["STARTED"] = server " is started."
  status["STOPPED"] = server " is stopped."
  status["STARTING"] = server " is starting."
  if ( toupper($0) ~ pattern) { 
     a=toupper($NF)
     sub(/\.$/,"",a)     
     print status[a]      
  }
 }'

keep up the good work

slakmagik · 02-27-2008, 07:44 AM

Quote:

Originally Posted by piercey

How does this look? Any suggestions for improvements? I'm not very familiar with bash coding etiquette so if there's a better way to do it I'm interested to hear

Cheers,

As far as less drastic revisions, I write functions as

Code:

get_server_status() {
    foo
}

rather than

Code:

get_server_status()
{
    foo
}

but I'm probably in the minority there and that's purely style and irrelevant to anything else.

Less trivially, unless there's a reason not to, I'd get in the habit of using $(foo) for command expansion rather than `foo`. I usually use `foo` on the command line because it's quicker but $(foo $(bar)) sort of stuff nests better. Lastly, functions can take arguments, so I'd probably delete the assignments to SERVER and say

get_server_status SERVER1
get_server_status SERVER2

and replace all $SERVER instances in the function with $1.

Actually, lastly lastly, you might want your functions and scripts returning exit codes. That's probably why serverStatus.sh returns 0 no matter what - it doesn't set an exit code and return >0 when it can't get a status. But, yeah, like ghostdog74 says, "keep up the good work".

piercey · 02-27-2008, 10:21 AM

Thanks for the help guys, I really appreciate it