Shell Programming and Scripting

Hi there, I am new to scripting and need your help showing me how to create a script that does ssh on multiple servers run remote commands e.g. checking a process and report the outcome to one of the servers lets name it server1, regards..Bader

What have you done so far?

from the server where I need the report on, I created a list of all servers that I need to generate the report from called it server list so wrote something like this

Code:

for i in `cat /opt/scripts/server list`
do, ssh $i "ps -ef | grep process name > /tmp/report"
done

---------- Post updated at 08:00 AM ---------- Previous update was at 07:49 AM ----------

Hi Zaxxon, is there a better way to do this, again, I am still learning this and don't have a big knowledge when it comes to writing scripts

Not sure if this is a typo, but a comma will not work to separate commands. Use a semicolon or start a new indented line do; ssh ....
Also the blank between "server list" might not work. I never use filenames with a blank when I have the choice and use a dot or underscore to enhance readability of them.

You write the output of grep to each server. Don't you want that centralized on the host you are issuing this command from?

Also please use code tags when posting code, data or logs etc.

Code:

$ cat server_list
host1
host2
host3
$ while read LINE; do
     printf "${LINE}: "
     ssh $LINE "ps -ef| grep <processnameinhere>" >> mylist.out
done < server_list

By adding the printf on the line that is being read, you know which element of your list is currently being processed. The output of the ssh command is written after the host name.
Try something like this. All goes to a local file from the machine where you issue the command.
If the ssh gets stuck after executing the first cycle, add a -n to the ssh call.

ssh in a loop can always be a bugger when you're first starting off in scripting. Firstly, the reason it can be such a bugger is because of how ssh handles terminals, when the ssh command completes it exits out of the terminal which in turn will cause your script to fail. Very frustrating!

So, to resolve this you can do 1 of 2 things. You can either tell ssh to use a null terminal or you can use exec to read in your file which will in turn cause your loop to iterate appropriately.

Also, make sure that when you're doing your output redirection that you're appending (>>) vs. rewriting (>)
ssh null terminal

Code:

for i in $(cat serverlist.list)
do
   ssh -n $i "ps -ef | grep process_name" >> /tmp/report
done

exec ssh

Code:

exec < server.list
while read SERVER; do 
    ssh $SERVER "ps -ef | grep process_name" >> /tmp/report
done

---------- Post updated at 09:48 AM ---------- Previous update was at 09:46 AM ----------

Good point, I didn't catch that his quotes were around the whole of the command. . Yes, depending on where your quotes are... it will cause your output to either go to the remote box or to go to your local box.

Thank you guys , you have been great.