python - 调用 pexpect.spawn 时，生成的程序会立即开始执行吗？

Question

pexpect.spawn 对象是否处于非事件状态，直到 expect(或 interact、send 等)被调用，还是被调用的进程立即开始？例如:

import pexpect
process = pexpect.spawn("echo HELLO")
print ("Process created? Or run?")
process.expect("HELLO")

当 print 语句出现时，pexpect 已经在幕后运行了 echo 命令，只是推迟让它返回，直到 expect 调用已处理？或者在第一次调用 expect 或类似函数之前什么都没发生(echo 没有运行)？

干杯

Answer 1

当传递命令时，pexpect.spawn() 立即 fork 并调用命令。您的示例中的 echo 命令已经运行。

这隐含在 spawn constructor documentation 中:

This is the constructor. The command parameter may be a string that includes a command and any arguments to the command. For example::

child = pexpect.spawn ('/usr/bin/ftp')
child = pexpect.spawn ('/usr/bin/ssh user@example.com')
child = pexpect.spawn ('ls -latr /tmp')

You may also construct it with a list of arguments like so::

child = pexpect.spawn ('/usr/bin/ftp', [])
child = pexpect.spawn ('/usr/bin/ssh', ['user@example.com'])
child = pexpect.spawn ('ls', ['-latr', '/tmp'])

After this the child application will be created and will be ready to talk to.

我已经通过查看 source code 确认了这一点;构造函数调用 _spawn()，记录如下:

This starts the given command in a child process. This does all the fork/exec type of stuff for a pty. This is called by __init__. If args is empty then command will be parsed (split on spaces) and args will be set to parsed arguments.