Friends,

I am developing a network application. So I have to login into remote PCs one by one and do some sort of work.

I am programming in C lang and distro is fedora 6.

For the remote login I m using SSH.

But wen I execute command "ssh <host ip>" programmatically then it asks me for the password entry. (expects pass entry from STDIN).

What I want is, non interactive password entry. Means If I have to interact with 5 client nodes then I have a text file which has IP addresses and corresponding passwords stored in it, and at the time of password entry it should read from text file, not prompting me on stdout for password entry !!

I know if u set ssh keys accordingly then it will not ask for password but for that also U must have to go through interactive password prompt for first time.

I heard about the pseudo terminals. One of my friend told me that if u use pseudo terminal then u can solve your problem.

but how, I dont know !! (I wanna do this programmatically)

plz help me. Is there any good link or tutorial or example program ??

any kinda help will be appriciated.

thnx

Libexpect can do this sort of stuff.

See this page.

Take a look at man ssh-keygen.

You'll need to generate a public key without a passphrase (just hit the return key when prompted) and copy that to the home directory's .ssh/authorized_keys file on the remote machines. When you ssh server, you won't be asked for a password.

Also, in the .ssh directory (on your controlling machine) create a file config with content like this for every machine you ssh to:
It would be useful to enter the remote host name(s) is /etc/hosts while you're at it.

When you execute ssh-keygen on a machine, two files will be created in the .ssh directory: id_dsa and id_dsa.pub. The id_dsa file is the private key, the id_dsa.pub file is the public key (the one that gets copied to a remote machine). Once done, login is not required.

Note, however, that the first time you connect to any machine with ssh you will be prompted to add an entry in known_hosts for the machine you're connecting to (no convenient way around that one).

Again, see man ssh-keygen.

thnx matthewg42

u have suddgested me the exact point i m expecting.

thnk u very-very much.

expect is a horrible solution *if* there are formal application specific ways to do this instead.. use preshared ssh keys and you will have a much better solution.

Acid is quite right, expect is not generally a good solution for automating logins with ssh since there is already an existing mechanism and you will have to store the passwords somehow, and doing this is likely to be insecure. I mentioned expect only because the OP asked specifically about pseudo terminals.

I did actually once write a login manager/convenience tool using expect, which used ssh, rsh and even telnet, but boy did I feel dirty doing it...

well yeah it's often a bit of a guessing game whether you answer the actual question or the question that you think they should be asking...