To execute two commands in a single line remotely

ZAMO · 10-30-2008, 09:23 AM

Hi all,

I need some help here. I need a help to pipe two commands. The purpose is to execute a command using ssh on other machine.
Say am in server1, I want to run the command as follow

Code:

server1$ssh server2 ls -lt /home/zamo |head -2

What I need is to include the hostname of "server2" also in the same line.
Any idea.I tried with the following , but failed.

Code:

server1$ssh server2 hostname; ls -lt /home/zamo |head -2

Here the second command fails.

david1941 · 10-30-2008, 09:40 AM

Works on my machine with hosts file. also works with $ ssh myuser@server2.domain ls |grep filename That may work for you.

Dave

dv502 · 10-30-2008, 11:03 AM

If you try to execute a command over ssh, the password prompt stops you from doing that.

You need to create private/public ssh keys without a passphrase. This will allow you to execute remote commands with ssh to a server without being prompted for a password.

Once you have it setup, you execute the command as follows:

ssh user@server2 'ls -lt /home/zamo |head -2'

http://www-128.ibm.com/developerwork...ry/l-keyc.html

This website shows how to create ssh keys for authentication. It also explains the risk of logging into a ssh server without a password.

david1941 · 10-30-2008, 01:27 PM

Sorry, dv502 is correct, I had assumed you were using pub/pri keys.
Dave

ZAMO · 10-30-2008, 10:20 PM

Thank you both.

Am using Pub key authentication and the trust is there with both the servers. (no passwd required).

I am trying to know , how to execute 2 commands in a single line in ssh like we do on a local shell.

Code:

 hostname; ls -lt /home/zamo

jschiwal · 10-30-2008, 10:24 PM

Put your oneliner in single quotes so that it is a single argument to ssh.

ZAMO · 10-30-2008, 11:02 PM

Thanks GURU,

Its working fine. Another short question by the way .
The command

Code:

server1$ssh server2 'hostname; ls -lt /home/zamo |grep -v total|head -1'

give the output as follows;

Code:

server2
drwxrwxr-x  2 zamo zamo  4096 Oct 30 04:04 newfile

Is there a way to print the output as

Code:

server2 drwxrwxr-x  2 zamo zamo  4096 Oct 30 04:04 newfile

jschiwal · 10-30-2008, 11:18 PM

The grep part will make that hard because piping to "tr '\n' '\0' after the hostname command will cause the server name and the total line to be on the same line.

There are probably better ways of doing this:
ssh user@host "(hostname; ls -l | head -n 2) | sed -n '1H;/total/d;${H;g;{ s/\n/ /g};p}'"

I needed to change the single quotes to double quotes because the sed command uses single quotes.

dv502 · 10-30-2008, 11:25 PM

Code:

'echo -ne $HOSTNAME \\t ; ls -lt /home/zamo |grep -v total|head -1'

or

Code:

'echo -ne `hostname` \\t ; ls -lt /home/zamo |grep -v total|head -1'

These two will give you the output you requested above, everything on one line. If you use the second one enclosed the hostname in back ticks. This will execute the hostname command. If not, it will echo the word hostname.

Hope this helps...

ZAMO · 10-31-2008, 12:19 AM

Thanks dv502,

Its working fine.
I have another question , and i think it will be good to continue that with the same thread, so that you guys can understand it better.

In

Code:

'echo -ne $HOSTNAME \\t ; ls -lt /home/zamo |grep -v total|head -1'

The hostname outputs server2.mynetwork.com. I just want the server2 only.
So am trying with

Code:

'echo -ne $HOSTNAME |awk -F\. '{print $1F}'  ; ls -lt /home/zamo |grep -v total|head -1'

and it is working. To bring the output in the same line am try with

Code:

'echo -ne $HOSTNAME |awk -F\. '{print $1F}' \\t ; ls -lt /home/zamo |grep -v total|head -1'

for that am getting the error

Code:

awk: cmd. line:2: fatal: cannot open file `t' for reading (No such file or directory)

Is there a way (or any alternate)to use \\t after awk -F\. '{print $1F}'

dv502 · 10-31-2008, 01:00 AM

Have you tried the second one?

Code:

'echo -ne `hostname` \\t ; ls -lt /home/zamo |grep -v total|head -1'

ZAMO · 10-31-2008, 01:26 AM

Code:

'echo -ne `hostname` \\t ; ls -lt /home/zamo |grep -v total|head -1'

is working

dv502 · 10-31-2008, 01:31 AM

Glad it work