使用子进程的Python利用

Question

I have a small program (Program A) that asks for a password, and if the password is correct, it opens a shell. I want to make another program (Program B) in python that calls Program A and gives the password as input, so that the shell is opened.

I'm doing the following, but the program just terminates, without letting me use the shell.

p = subprocess.Popen("./ProgramA", stdin=subprocess.PIPE)
p.communicate("password")

When running Program B my terminal looks like:

~/Desktop/$./ProgramB
Password: Here is your shell.
~/Desktop/$ (this is not the shell opened by program A)

How can I fix this?

Answer 1

The shell started by ProgramA inehrits stdin from its parent process, so it inherits the pipe. The pipe is already closed at that point, so the shell exits.

You would want to keep the terminal as stdin, but then it will be hard to fake the password input.

Answer 2

Popen.communicate() closes stdin of the subprocess and waits until it terminates - it is expected behaviour. What you need is simply p.stdin.write("password") .

Answer 3

Assuming this is linux or osx, programs typically operate differently if stdin is a pipe instead of a terminal and they also "step around" stdin and read the terminal for the password. In your case, the program likely saw no terminal and exited. Try using the python pexpect module or read its source to see how to open a pty for stdin.