How to write data to a specific fd using Python Pwntools

Question

I'm trying to use pwntools's process and to write a string to a specific fd

In the documentation, there is a parameter to process of stdin and stdout but I do not understand how to use it correctly. I tried using open("<named pipe">) since I saw in the documentation that a file object is a valid argument, but then remembered that it will not work since writing is blocked until someone starts reading.

Salt · Accepted Answer · 2025-04-17 11:46:54Z

1

Just so there’s no magic: you can only write data into a process’s STDIN; STDERR is always an output FD you can only read or redirect. If you want to feed your program on fd 2 (e.g. it actually does an os.read(2,…)), you must dup your stdin‐pipe onto fd 2 in the child before exec. Otherwise just use send/sendline to write to STDIN and stderr=PIPE (or a file) to capture its error‐output.

answered Apr 17 at 11:46

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LavaTime Sep 6 at 9:23

How might I perform what you suggested? i.e, "dup your stdin-pipe onto another fd in the child before exec........"

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