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How do you stream data into the STDIN of a program from different local/remote processes in Python?

Answer 1

+1 A:

This isn't portable, but on many Linux systems, you can write to

/proc/$PID/fd/0

I think this may be one of a very limited number of potentially complicated options if you don't have any other control over the remote process.

Michael Mior 2010-09-25 01:42:43

Michael. Your solution scheme does work locally. But how do you do it remotely? Also, any python suggestions?

OTZ 2010-09-25 01:57:19

Actually, I do know how one could do it remotely: use sshfs or some other virtual file system and mount the target file. But such methodology tends to be less robust and hold less integrity. So some other way is desired.

OTZ 2010-09-25 02:01:44

You don't need to use sshfs. Just use SSH and pipe in the data. Something like `ssh $SERVER "cat - > /proc/$PID/fd/0"`. Or use Alex's suggestion and check out `paramiko`.

Michael Mior 2010-09-25 02:43:37

Right. But in that case, we'd be relying on cat's stdin and stdout. So im not sure it'd be more efficient than sshfs. Either way, i think i have enough material to code further (thanks to you and Alex).

OTZ 2010-09-25 04:31:41

No problem. You can use something like `netcat` if you're worried about the overhead of encryption via SSH. You can also try `ssh -c blowfish` to use the faster Blowfish cipher.

Michael Mior 2010-09-25 05:18:52

Answer 2

+1 A:

In most platforms (i.e., operating systems), an existing process's existing file descriptors are inviolate -- the operating system, striving to guarantee process integrity, will be designed to not allow a separate, unrelated process to alter those file descriptors.

Nevertheless, if you do specify a very specific and well-identified platform (ideally including the exact version and release of the operating system in question, since security does tend to get tightened in successive releases compared with preceding ones), it's quite possible that there will be available tricks for your purposes. For example, you may be able to exploit some of the hooks which the operating system intends to be used for "remote debuggers" attaching themselves to existing processes -- if, that is, your very specific OS does offer such hooks (not all do!).

But, if you want a cross-platform solution, no way.

So, I recommend you edit your question, and in particular replace one of the tags with the name of the "one and only" OS you really need to support (in the Q's edited text, please be as specific as possible about the exact versions and releases you absolutely do need to support -- Python has very little indeed to do with the issue, as you need to operate at specific-OS levels, so there's no real need to similarly pinpoint the Python version).

Alex Martelli 2010-09-25 01:46:04

Edited. I should have mentioned it first. The intended OS for this question is Linux. Thanks for pointing it out.

OTZ 2010-09-25 01:52:43

@OTZ, you're welcome. Then use @Michael's solution -- do it remotely via `ssh` of course (or directly with third-party Python extension package `paramiko`, which lets you speak "sshese" directly from your Python code, without needing to shell out to the `ssh` command-line client!-). Of course, you need credentials to authenticate yourself to the remote node's `sshd` (but then it's obvious that security _at least_ requires any remote process able to do such things to be safely authenticated with the node in question, right?-).

Alex Martelli 2010-09-25 02:01:34

@Alex Still don't know how to get the file-descriptor given only pid and hostname remotely, but i'll look further. If there isn't a good way to do so in python, sshfs mounting I commented (to Michael's answer) may be a good compromise.

OTZ 2010-09-25 02:10:19

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How do you stream data into the STDIN of a program from different local/remote processes in Python?

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