Some shell programs expect interactive user input. For example if you spawn a root shell with “su” the program asks your for a password. There is no way to pass this password to “su” as a parameter. Another example is to automate an FTP session: start FTP client, provide user and password, do a couple of up- and downloads and exit.
These kind of processes can be automated in Python using the pexpect module. Here is an example on how to run a command as root, interactively sending the password to the waiting process:
import pexpect, sys # spawn a root shell proc = pexpect.spawn("su") proc.logfile = sys.stdout # wait until the program finds the string "Password" in the output of the command proc.expect("[Pp]assword") # now send the password to the waiting shell proc.sendline("yourRootPassword") # wait until the command completed (assuming that "#" is part of the next prompt) proc.expect("#") # run the whoami command proc.sendline("whoami") # wait for next prompt proc.expect("#") # ...
This gives the following output:
[email protected]:~$ python script [sudo] password for myuser: ************** [email protected]:~# whoami whoami root