python - Windows subprocess.Popen 没有 shell=True 的批处理文件

Question

我有一个运行 lessc 的函数(使用 npm install -g less 安装):

>>> import subprocess
>>> subprocess.Popen(['lessc'])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\subprocess.py", line 679, in __init__
    errread, errwrite)
  File "C:\Python27\lib\subprocess.py", line 896, in _execute_child
    startupinfo)
WindowsError: [Error 2] The system cannot find the file specified

不幸的是，除非我添加 shell=True，否则它不起作用:

>>> subprocess.Popen(['lessc'], shell=True)
<subprocess.Popen object at 0x01F619D0>

如何在不使用 shell=True 的情况下让 lessc 运行？

Answer 1

来自https://docs.python.org/3/library/subprocess.html#subprocess.Popen和 https://docs.python.org/2/library/subprocess.html#subprocess.Popen :

You do not need shell=True to run a batch file or console-based executable.

已经cited by @JBernardo .

那么，让我们试试:

lessc 实际告诉的地方

C:\Users\myname\AppData\Roaming\npm\lessc
C:\Users\myname\AppData\Roaming\npm\lessc.cmd

也就是说，要执行的文件是 lessc.cmd，而不是某个 .bat 文件。事实上:

>>> import subprocess
>>> subprocess.Popen([r'C:\Users\myname\AppData\Roaming\npm\lessc.cmd'])
<subprocess.Popen object at 0x035BA070>
>>> lessc: no input files

usage: lessc [option option=parameter ...] <source> [destination]

因此，如果您指定完整路径，这确实有效。我假设当你有一个错字 this experience .可能是您编写了 .bat 而不是 .cmd？

---

如果您不想将 lessc 的完整路径修补到您的脚本中，您可以为自己烘焙一个where:

import plaform
import os

def where(file_name):
    # inspired by http://nedbatchelder.com/code/utilities/wh.py
    # see also: http://stackoverflow.com/questions/11210104/
    path_sep = ":" if platform.system() == "Linux" else ";"
    path_ext = [''] if platform.system() == "Linux" or '.' in file_name else os.environ["PATHEXT"].split(path_sep)
    for d in os.environ["PATH"].split(path_sep):
        for e in path_ext:
            file_path = os.path.join(d, file_name + e)
            if os.path.exists(file_path):
                return file_path
    raise Exception(file_name + " not found")

然后你可以这样写:

import subprocess
subprocess.Popen([where('lessc')])