Subprocess.poll（）错误地返回一个值

Question

test1.py：

process = Popen(["python","test2.py"]) 
time.sleep(3) 

alive = process.poll() 
if alive is None: 
    print "Still running" 
else: 
    print "Not running\r\n" 
    print "%r" % alive 

test1.py输出：

Not running
2

test2.py：

time.sleep(30) 
print "done" 

这是怎么回事？不应该返回“仍在运行”？

---

由于矛盾的结果，这里的全test1.py代码：

import cStringIO 
import os 
import cgi 
import time 
from subprocess import Popen 

def application(environ, start_response): 
    headers = [] 
    headers.append(('Content-Type', 'text/plain')) 
    write = start_response('200 OK', headers) 

    input = environ['wsgi.input'] 
    output = cStringIO.StringIO() 

    process = Popen(["python","test2.py"]) 
    time.sleep(3) 

    alive = process.poll() 
    if alive is None: 
     print >> output, "Still running" 
    else: 
     print >> output, "Not running\r\n" 
     print >> output, "%r" % alive 

    output.write(input.read(int(environ.get('CONTENT_LENGTH', '0')))) 
    return [output.getvalue()] 

---

更新test1.py：

process = Popen(["python","C:/wamp/www/python/popen/test2.py"], shell=True) 
    time.sleep(5) 

    alive = process.poll() 
    if alive is None: 
     #print >> output, "%r" % alive 
     print >> output, "Still running" 
    else: 
     print >> output, "Not running" 
     print >> output, "%r" % alive 
     print >> output, "Current working dir : %s" % os.getcwd() 
     print >> output, os.strerror(0) 

更新的输出：

Not running
0
Current working dir : C:\wamp\bin\apache\apache2.2.22
No error

Answer 1

如果POPEN（）无法找到test2.py，它产生的错误 “没有这样的文件或目录”，并将errno 2.该错误号被以投票方式返回（）。既然你似乎是贯穿WSGI这个脚本，有些事情似乎要吞你的标准错误，你不会看到错误消息：

$ cat test1.py 
from subprocess import Popen 
import time 

process = Popen(["python","doesnotexist.py"]) 
time.sleep(3) 

alive = process.poll() 
if alive is None: 
    print "Still running" 
else: 
    print "Not running\r\n" 
    print "%r" % alive 
$ python test1.py 
python: can't open file 'doesnotexist.py': [Errno 2] No such file or directory 
Not running 

2 

现在，这个问题可能是因为你的脚本的当前工作目录未被前端服务器设置为脚本目录，请尝试打印os.getcwd（）以查看它是否符合您的期望。

Answer 2

根据this

的2退出状态指示与执行命令的外壳的问题。您是否尝试过直接在shell中运行test2.py以验证它是否存在问题？正如Lie指出的那样，shell可能找不到你要执行的文件，尽管可能会有另一个问题导致它被破坏。