topic Re: How to send commands to some ports using script? in Operating System - Linux

How to send commands to some ports using script?

Shashikiran_1 — Tue, 17 May 2005 11:19:54 GMT

Hi ,

I need to telnet to a Unix box using some ports. And send some commands.
Eg :
telnet
send ctrl+A
Now I will get a prompt.

Now send some commends.

send brk
send chkstatus

I tried using label . It didn't work.

e.g. : telnet 192.168.10.10 4006 < ^A
brk
chkstatus
LABEL

How can I send control+A and some commands . can some one throw some light on this?

Thanks & Regards

Re: How to send commands to some ports using script?

Dave Falloon — Tue, 17 May 2005 14:31:13 GMT

I would use netcat and perl to do this, something like this:

perl -e 'print \cA' |nc

I can't remember if thats the right syntax for ctrl+A, you may have to change that to the decimal equivalent, I think its 001?

--Dave

Re: How to send commands to some ports using script?

Stuart Browne — Tue, 17 May 2005 17:53:41 GMT

The reason why the 'here-document' didn't work as an input into telnet is because it doesn't wait.

To use a pipe and telnet, you have to force sleeps in to wait for the output, i.e.:

(
echo ^A
sleep 1
echo brk
sleep 1
echo chkstatus
sleep 1
) | telnet 192.168.10.10 4006

But the better option would be to use 'expect', if there is some sort of output expected after each command.

Re: How to send commands to some ports using script?

Gopi Sekar — Wed, 18 May 2005 01:15:03 GMT

'expect' is the right method to use for this.
check man expect to find out how to achieve this.

you can also do through pipe like this,

mkfifo pipe # this will create the pipe
cat > pipe # this will open the pipe and wait for input, then go to another session

telnet host < pipe # this will open telnet session with input from pipe

now whatever sent in pipe will be piped to telnet. you can use this method to control it from script.

Regards,
Gopi

Re: How to send commands to some ports using script?

Dave Falloon — Wed, 18 May 2005 13:04:39 GMT

I played with this a little more, here is another useful way to do this.

printf \\001\\nbrk\\nchkstatus|nc 192.168.10.10 4006

the nice thing about netcat is you don't have to wait for responses, that is built in to the program.

check out the man page for more info:

man nc

--Dave