python subprocess.Popen vs os.popen

Question

我正在尝试在我的python脚本中获得以下shell命令的输出，

hadoop fs -ls /projectpath/ | grep ^d | grep -v done | head -1 | awk {'print $8'}

我可以通过os.popen成功获取输出，如下所示：

import os
cmd = "hadoop fs -ls /projectpath/ | grep ^d | grep -v done | head -1 | awk {'print $8'}"
p = os.popen(cmd,"r")
while 1:
    line = p.readline()
    if not line: break
    print line

但是从Python2.6开始就不推荐使用os.popen()了，所以我想用subprocess.Popen()函数替换上面的代码片段。

但是下面的subprocess.Popen()代码片段给出的结果与上面的代码片段不同。

import subprocess as sub
import shlex
cmd = "hadoop fs -ls /projectpath/ | grep ^d | grep -v done | head -1 | awk {'print $8'}"
args = shlex.split(cmd)
p = sub.Popen(args,stdout=sub.PIPE,stderr=sub.PIPE)
output, errors = p.communicate()
print output

上面的命令只是给出了命令的'hadoop fs -ls /projectpath/'部分的输出。我已经尝试在几个参考文献(http://docs.python.org/2/library/subprocess.html#popen-objects，Python, os.system for command-line call (linux) not returning what it should?)中查找subpocess.Popen()，但无法让它执行字符串cmd中的命令。谁能指出我做错了什么？

Answer 1

试试这个：

cmd = "hadoop fs -ls /projectpath/ | grep ^d | grep -v done | head -1 | awk {'print $8'}"
p = sub.Popen(cmd,stdout=sub.PIPE,stderr=sub.PIPE, shell=True)