Ssh in the background

Shell Programming and Scripting
1

Hi,

I am trying to execute an ssh command in my script.
ssh abcd@server_name
After this command it actually logs in to the server asking for password prompt and then actually logs in to the server.

I want all this to be happening in the background and show noithing in the output of my script.
I just want to login to the server in the background and check if the file exists and sftp it.

How do i do it ? without showing anything on my script.

2

You should work with private/public keys to avoid the login and use scp instead of sftp.

3

Redirect stdout and stderr to a log file (for error analysis) or to /dev/null.

1 Like
4

Let me get this straight. After connecting via ssh to a remote server, you want to check whether a certain file exists there and if it doesn't, upload it from your localhost using sftp, correct? Please confirm and we'll be more than glad to help.

5

1 use password less ssh concept into use.
2 do validation of required files
3 if pass, sftp the file

6

Yes thats correct....just that mre than uploading I would be getting some files from that server.

I tried what rudic suggested and it has helped.
Would like to know now:

Once I have logged in...i want to sftp file to another server .,....how can I do that ?
I do not wan the sftp> prompt to be shown.
The file should be sftped in the background.

Can you please help ?

7

Ok. So you're logged in to your first server, and from there you're going to sftp the file to another server.
Try this:

sftp user@2ndServer <<END_SEND
	cd $directory
	put $file
	quit
END_SEND

This code snippet makes the following assumptions:

  1. the 1st server is both a server (from your localhost's point of view) and a client (from the 2nd server point of view).
  2. The remote sftp service is listening on the default port, that is, port 22 (other wise, you need to add the -oPort switch, like this: -oPort=1111 , for example).
  3. In your script, before you use this code, you need to set the following variables: directory (for remote directory, use an absolute path), file (the file you want to sftp to the 2nd server)

Let me know how it goes.

8

Thanks.
Will try the above ...just wanted to know what does END_SEND stand for here ?

9

END_SEND is an identifier of what is called a here document. Check this link for a more thorough explanation of here documents and what they are usually used for. Also, Wikipedia has a nice article about here documents with examples.