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Old 08-27-2008, 07:06 AM   #1
gt2nv
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Question about ssh and bash scripting......


I am trying to write a bash script that will ssh to a machine, run a command, display the result back to me and then exit. Right now i am not having much luck, and was wanting to know if i could get some help. Thanks in advance.
 
Old 08-27-2008, 07:11 AM   #2
matthewg42
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What seems to be the problem that you are having? Do you need to know how to set up public key authentication?
 
Old 08-27-2008, 07:15 AM   #3
gt2nv
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Here is what i added to my script.


#!/bin/bash
#
#
ssh -p22 machinex
pdsh -w server[1-4] uptime
exit
exit 0

The only thing that it is doing is sshing to machinex and no executing the command or exiting. Maybe i am trying to do something that is not possible. I am kinda new to bash scripting.
 
Old 08-27-2008, 07:39 AM   #4
matthewg42
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You can provide remote host commands on the invocation line for ssh.

You might want to enclose the whole command in single quotes to prevent the local shell from expanding the glob pattern "server[1-4]" (in the case where there exists some local files which match this pattern).

There is also no need to exit from the ssh connection - when you provide a command in this way, the ssh session terminates when the command is complete.

The -p22 in your example is redundant, as port 22 is the default port for ssh.

Code:
ssh user@host 'pdsh -w server[1-4] uptime'
 
Old 08-27-2008, 07:41 AM   #5
gt2nv
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I will give that a shot. Thank you so much!!
 
Old 08-27-2008, 07:43 AM   #6
gt2nv
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that worked!!!! Thank you very much!!!!
 
Old 08-27-2008, 07:50 AM   #7
colucix
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I would add that if you want to run more than one command, you can concatenate them using logical operators, like && and || or put them in a "here document" like this:
Code:
ssh user@host <<-EOF
  cd /path/to/dir
  whoami
  pdsh -w server[1-4] uptime
  cd /path/to/some/other/dir
  exit
EOF
Moreover, to avoid interactive input for password, you have to setup a public/private key authentication, as already suggested by matthewg42.
 
Old 08-27-2008, 08:07 AM   #8
gt2nv
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Quote:
Originally Posted by colucix View Post
I would add that if you want to run more than one command, you can concatenate them using logical operators, like && and || or put them in a "here document" like this:
Code:
ssh user@host <<-EOF
  cd /path/to/dir
  whoami
  pdsh -w server[1-4] uptime
  cd /path/to/some/other/dir
  exit
EOF
Moreover, to avoid interactive input for password, you have to setup a public/private key authentication, as already suggested by matthewg42.
Thanks, i will give that a shot!
 
Old 08-27-2008, 09:02 AM   #9
marozsas
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Quote:
Originally Posted by colucix View Post
[CODE]ssh user@host <<-EOF
Hi Colucix !
Great tip.
But I was unable to find in documentation (I guess in the bash documentation) the meaning of that "-" in front of "EOF". Can you explain it, please ?

Your code works even in the absence of that "-"....
 
Old 08-27-2008, 09:12 AM   #10
vladmihaisima
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Check here http://tldp.org/LDP/abs/html/here-docs.html, example 18-4.
 
Old 08-27-2008, 09:13 AM   #11
colucix
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Indeed it is not useful in my example. From the Advanced Bash Scripting Guide:
Quote:
The − option to mark a here document limit string (<<−LimitString) suppresses leading tabs (but not
spaces) in the output. This may be useful in making a script more readable.
This means you can safely indent statements inside a here document using TABs, since they are stripped out by the shell and not passed as input. One of the many nuances in shell scripting!
 
Old 08-27-2008, 09:17 AM   #12
matthewg42
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That leading tabs thing is great - I learned something awesome today!
 
Old 08-27-2008, 10:20 AM   #13
marozsas
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Quote:
Originally Posted by vladmihaisima View Post
Thanks, I learn one more thing today. great !

by the way, are your name a Hungary name ? My first name in hungary is "Mihay" my last name means "Rose" in hungary, and I have a close Hungary friend which his last name is "Sima" too...so it is too much coincidences to not be a hungary name....sorry if not.
 
Old 08-27-2008, 10:32 AM   #14
raconteur
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Quote:
Originally Posted by matthewg42 View Post
That leading tabs thing is great - I learned something awesome today!
Yep, same here (pun intended ) I've always left-justified my here documents and that does add some obfuscation to indented code. How did I miss this for so long, I wonder? Thanks for the tip.
 
Old 08-27-2008, 11:30 AM   #15
marozsas
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Thumbs up

Quote:
Originally Posted by colucix View Post
Indeed it is not useful in my example.
Sure it is usefull, at least to teach others.... So many comments about this trick !

cheers,
 
  


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