以bash命令的结果，并使用Python中它 [英] Taking the results of a bash command and using it in python

问题描述

我试图用Python语言编写一个code，将采取自上而下的一些信息，并把它放到一个文件中。
我只想编写应用程序的名称，生成文件。我遇到的问题是，我不能得到的pidof命令的输出，所以我可以在Python中使用它。我的code是这样的：

I am trying to write a code in python that will take some information from top and put it into a file. I want to just write the name of the application and generate the file. The problem i am having is that i can't get the output of the pidof command so i can use it in python. My code looks like this :

import os

a = input('Name of the application')
val=os.system('pidof ' + str(a)) 
os.system('top -d 30 | grep' + str(val) + '> test.txt')
os.system('awk '{print $10, $11}' test.txt > test2.txt')

问题是，VAL总是0，但该命令返回我想要的PID。任何投入将是巨大的。

The problem is that val always has 0 but the command is returning the pid i want. Any input would be great.

推荐答案

一起来，使用输入（）气馁，因为它要求用户输入有效Python的前pressions。使用的raw_input（）而不是：

First up, the use of input() is discouraged as it expects the user to type in valid Python expressions. Use raw_input() instead:

app = raw_input('Name of the application: ')

接下来，从的返回值系统（'的pidof'）不是PID，它是从出口code中的的pidof 命令，失败即零成功，非零。你想捕捉的pidof的输出 。

Next up, the return value from system('pidof') isn't the PID, it's the exit code from the pidof command, i.e. zero on success, non-zero on failure. You want to capture the output of pidof.

import subprocess

# Python 2.7 only
pid = int(subprocess.check_output(['pidof', app]))

# Python 2.4+
pid = int(subprocess.Popen(['pidof', app], stdout=subprocess.PIPE).communicate()[0])

# Older (deprecated)
pid = int(os.popen('pidof ' + app).read())

下一行后失踪的的grep 的空间，并会导致像 grep1234 命令。使用字符串格式化操作符％将使这更容易一点的景点：

The next line is missing a space after the grep and would have resulted in a command like grep1234. Using the string formatting operator % will make this a little easier to spot:

os.system('top -d 30 | grep %d > test.txt' % (pid))

第三条线被严重引用，应该引起语法错误。当心单引号单引号里面。

The third line is badly quoted and should have caused a syntax error. Watch out for the single quotes inside of single quotes.

os.system("awk '{print $10, $11}' test.txt > test2.txt")

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