Basic tutorial on installing and using the command line Interaction module pexpect in Python

Pexpect is a pure Python module that can be used to interact with command line commands such as ssh, ftp, passwd, and telnet. It is particularly useful in Linux systems, next, let's take a look at the basic tutorial of installing and using the command line interactive module pexpect in Python: I. Installation
1. Install the easy_install Tool

wget http://peak.telecommunity.com/dist/ez_setup.py

Python ez_setup.py install the easy_install tool (this script will be automatically searched and downloaded from the official website)

python ez_setup.py -U setuptools

Upgrade easy_install Tool

2. Install pexpect

easy_install Pexpect

Test:

[root@OMS python]# pythonPython 2.7.3rc1 (default, Nov 7 2012, 15:03:45)[GCC 4.1.2 20080704 (Red Hat 4.1.2-48)] on linux2Type "help", "copyright", "credits" or "license" for more information.>>> import pexpect>>> import pxssh>>>

OK has been installed.

Ii. Basic usage
1. run () function
The run function is relatively simple and can only implement simple interaction.

The Code is as follows:

Run (command, timeout =-1, withexitstatus = False, events = None, extra_args = None, logfile = None, cwd = None, env = None)

Run the command and return the result, which is similar to OS. system.
Example:

Pexpect. run ('LS-la') # Return Value (output, exit status) (command_output, exitstatus) = pexpect. run ('LS-l/bin', withexitstatus = 1)

2. spawn class
Spawn is more powerful than run to achieve more complex interaction

class spawn   __init__(self, command, args=[], timeout=30, maxread=2000, searchwindowsize=None, logfile=None, cwd=None, env=None)

Timeout specifies the timeout value for interaction;
Maxread sets the read buffer size. The maximum number of bytes that pexpect tries to read from the TTY (Teletype terminal) each time;

Searchwindowsize specifies the position where pattern matching is performed from the input buffer. By default, pattern matching is performed from the start;

The logfile parameter specifies the log record location.
Working Process:

# Step 1 establish a connection with the terminal child = pexpect. spawn (the 'scp foo user@example.com :. ') # Step 2: Wait for the terminal to return specific content child. keep CT ('password: ') # Step 3 send commands Based on the returned content to interact with child. sendline (mypassword)

3. pxssh class
Pxssh is a derived class of pexpect and is used to establish an ssh connection, which is better than pexpect.

Login () establishes an ssh connection to the target machine;
Logout () releases the connection;
Prompt () is usually used to wait for the end of command execution.

Iii. Instances
Write a script to send commands to the remote server and return results.
Script content:

#!/usr/bin/python #2013-01-16 by larry import pexpect def login(port,user,passwd,ip,command):   child=pexpect.spawn('ssh -p%s %s@%s "%s"' %(port,user,ip,command))   o=''   try:     i=child.expect(['[Pp]assword:','continue connecting (yes/no)?'])     if i == 0:       child.sendline(passwd)     elif i == 1:       child.sendline('yes')     else:       pass   except pexpect.EOF:     child.close()   else:     o=child.read()     child.expect(pexpect.EOF)     child.close()   return o  hosts=file('hosts.list','r') for line in hosts.readlines():   host=line.strip("\n")   if host:     ip,port,user,passwd,commands= host.split(":")     for command in commands.split(","):       print "+++++++++++++++ %s run:%s ++++++++++++" % (ip,command),       print login(port,user,passwd,ip,command)  hosts.close()

Usage:

python scripts.py

The content of the host. list file is as follows:

192.168.0.21:22999:root:123456:cat /etc/redhat-release,df -Th,whoami192.168.0.21:22999:root:123456:cat /etc/redhat-release,df -Th,whoami

Returned results:

+++ ++ 192.168.0.21 run: cat/etc/redhat-release ++ Red Hat Enterprise Linux Server release 4 ++ + 192.168.0.21 run: df-Th ++ file system type capacity used available % mount point/dev/cciss/c0d0p6ext3 5.9G 4.4G 1.2G 80% // dev/cciss/c0d0p7ext3 426G 362G 43G 90%/opt/dev/cciss/c0d0p5ext3 5.9G 540 M 5.0G 10%/var/dev/cciss/c0d0p3ext3 5.9G 4.1G 1.5G 74%/usr/dev/cciss/c0d0p1ext3 487 M 17 M 445 M 4%/boottmpfs tmpfs 4.0G 0 4.0G 0%/dev/shm ++ +++ 192.168.0.21 run: whoami ++ root