CODEWITHSUNDEEP
cssh
m4n07
m4n07

Reputation: 2297

Interpreting commands sent over ssh

Say from a PC, a SSH client will be sending commands (such as custom commands for my program e.g. ("show list of devices")). On my Linux end I want to have a program which will recieve these commands sent over SSH and execute them.

I'm trying to write a c program running on the linux side to interpret the custom commands sent and process them as per my requirements. Any suggestions as to how I would achieve this?

UPDATE: There are 2 programs here. The 1st program running on a PC1 which gives a command line interface, by which the user can issue commands. The second program is on the Linux end(PC2) which has to receive these commands and process it. Right now I'm thinking on the second program on how to get those commands.

Upvotes: 1

Views: 343

Answers (2)

Mats Petersson
Mats Petersson

Reputation: 129524

This is really about communicating with another program, and has very little to do with ssh - since ssh is just the "pipework" - what you need to do is open two pipes (one for stdin, one for stdout) to your application [which happens to be ssh], and write to the stdin pipe, and read from the stdout pipe. If you can do this with a regular (local) program, then all you need to do is add "ssh" to the line you are executing, and you're done.

If you don't understand what this means, look up exec, popen, pipes, etc.

You obviously also need the program at the other end to read from its stdin and write to its stdout. But that's normal command line programming, so I don't see that as a huge problem.

Upvotes: 0

perreal
perreal

Reputation: 98108

You can do this in at least two different ways:

  1. Execute the C program (say client) through ssh and send commands as arguments. The client parses arguments and does whatever. You need to run the client for each command.

  2. Your C program reads commands from the standard input, so you execute the C program over ssh once, and pipe your commands to ssh.

If your commands are not so frequent then do the 1st one. You can even execute ssh instances in the background and effectively run client commands in parallel. If you have a lot commands in sequence then implement the 2nd way. It will be harder to run them in parallel and relatively harder to parse commands since 1st way will give you each parameter as a different argument. With the second method, it will be much more efficient and faster to process frequent commands since you will not be establishing a connection and forking a process per command.

Upvotes: 2

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