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Full Discussion: Running function or command concurrently in a bash script
Top Forums Shell Programming and Scripting Running function or command concurrently in a bash script Post 302283869 by dj_bridges on Wednesday 4th of February 2009 09:19:44 AM
Old 02-04-2009
Otheus thanks for the rapid response. Yes you are right - I just want the script to constantly monitor the connection and start it again if it stops.

So if I run the script that you gave me it looks for the tunnel-keepalive.pid in /var/run, but nothing by this name appears there. So the script will never enter the while loop. The script doesn't seem to run based on the existence of a file in the local directory. I can only get it to run if I do this:

Code:
LOCK=/var/run/tunnel-keepalive.pid
echo $$ >LOCK #Puts the pid into a file called LOCK
LOCK=./LOCK
# start tunnel here

while [ -f $LOCK ]; do
   # Test to see if tunnel is still up, if not: start again
   sleep 5
done

I know that the above works - if I delete the file LOCK then the while loop stops, but I feel like I am missing the point or pulling the pid into a file - or could I just use the presence of any old file to maintain the while loop (and therefore the tunnel)?

Sorry in advance for my ignorance.....
Last edited by otheus; 02-04-2009 at 10:22 AM.. Reason: space between $$ >
 

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LEARN ABOUT DEBIAN

dns2tcpc

dns2tcpc(1)						      General Commands Manual						       dns2tcpc(1)

NAME

       dns2tcpc - A tunneling tool that encapsulate TCP traffic over DNS.

SYNOPSIS

       dns2tcpc [ -h ] [ -c ] [ -z domain zone ] [ -d debug_level ] [ -r resource ] [ -k key ] [ -f config_file ] [ -e command ] [ -T request type
       ] [ -l local_port ] [ server ]

DESCRIPTION

       dns2tcpc is a network tool used to encapsulate TCP communications in DNS. When connections are received on a specific port all TCP  traffic
       is sent to the remote dns2tcpd server and forwarded to a specific host and port. Multiple connections are supported.

       dns2tcpc was written for demonstration purposes.

OPTIONS

       -h     Help Menu

       -c     Enable DNS compression. When used, be sure that all relay and DNS server support compression and really use it.

       -z domain zone
	      Use this domain as endpoint.

       -d debug level
	      Change debug level. Levels available are 1, 2 or 3.

       -r resource
	      Remote resource to access.

       -k key Pre shared key used for authentication (identification).

       -f config file
	      Configuration file to use.

       -T request type
	      Request type to use. Actually only KEY and TXT requests are supported.

       -e command
	      Command to execute, I/O are redirected in the tunnel.

       -l local_port
	      Local port accepting incomming connections (or - for stdin on UNIX systems).

       -t connection timeout
	      Maximum DNS server's answer delay in seconds. A valid delay is between 1 and 240 seconds. Default is 3.

       server DNS server to use. The first entry in resolv.conf file will be choosen if the server is not specified.

CONFIGURATION FILES

       By default ${HOME}/.dns2tcprc is used if no configuration file is specified. Here is an example :

	      domain = dns2tcp.hsc.fr
	      resource = ssltunnel
	      local_port = 4430
	      enable_compression = 0
	      debug_level = 1
	      key = mykey
	      # DNS to use
	      server = ns.hsc.fr

EXAMPLES

       dns2tcpc -k mykey -z dns2tcp.hsc.fr mydns

	      Ask the dns2tcp server to list available resources.

       ssh -o 'ProxyCommand dns2tcpc -r ssh -l - -z dns2tcp.hsc.fr -k mykey mydns' myserver

	      Use dns2tcp as a proxy command with ssh. We try to connect to the ssh resource with the key 'mykey' and the DNS mydns.

       dns2tcpc -r socat-resource -e '/bin/bash -i' -k mykey -z dns2tcp.hsc.fr mydns

	      Use dns2tcp as a reverse shell, the remote shell will appear on the socat-resource.

       dns2tcpc -d 1 -f /dev/null -r ssl-tunnel -l 2000 -k mykey  -T KEY -z dns2tcp.hsc.fr mydns

	      Do  not  use the default configuration file, bind local port 2000 and forward all the traffic on the remote ssl-tunnel resource, use
	      the first debug level. Use KEY type DNS requests.

AUTHORS

       Olivier Dembour <olivier.dembour@hsc.fr>

SEE ALSO

       ssltunnel

																       dns2tcpc(1)
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