在python中调用命令行_如何在Python中调用外部命令？

水深无声 2023-03-05 12:58 21阅读 0赞

在python中调用命令行

In order **to run an external command within python env**, or start up a daemon process, or perhaps invoke a command and capture its output, **Python supports several methods for invoking an external command**.

为了**在python env中运行外部命令** ，或者启动守护进程，或者也许调用命令并捕获其输出， **Python支持多种方法来调用外部命令** 。

Choosing the method depends upon the requirement if there is a need to retain the output from the command, or send an input to the command, or have control over its lifecycle.

是否需要保留命令的输出或向命令发送输入或控制其生命周期取决于方法的要求。

### 子流程 **(**Subprocess**)** ###

**Subprocess** is the recommended module in python (version 3.5 +) to **execute an external command**. Using the call method of the **subprocess module**, an external command can be invoked within the python function.

**子进程**是python(3.5 +版本)中推荐的模块，用于**执行外部命令** 。 使用**subprocess模块**的call方法，可以在python函数内调用外部命令。

Python 3.6.8 (default, Apr 25 2019, 21:02:35)
    [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    
    >>> import subprocess
    >>> subprocess.call(['ls', '-l'])
    total 8
    drwxr-xr-x 4 XXXXX sw 4096 Oct  1 17:37 python_samples
    drwxr-xr-x 5 XXXXX sw 4096 Sep 29 19:53 venv
    0
    >>>

### 将输出重定向到文件 **(**Re-directing the output to the file**)** ###

In order to redirect the output to a file, using the with function to open the file and use **stdout** parameter.

为了将输出重定向到文件，请使用with函数打开文件并使用**stdout**参数。

Python 3.6.8 (default, Apr 25 2019, 21:02:35)
    [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    
    >>> import subprocess
    >>> with open('output.txt', 'w') as f:
    ...     subprocess.call(['whoami'], stdout=f)
    ...
    >>> exit()
    -bash-4.2$ more output.txt
    User

### 将参数作为输入从stdin传递到命令 **(**Passing an argument as input from stdin to command**)** ###

Using the **call()** . Open a file and pass the handle using the **stdin** parameter.

使用**call()** 。 打开文件并使用**stdin**参数传递句柄。

### 使用shell = True，可以将shell命令传递给call()函数。 **(**Using shell=True , a shell command can be passed to the call() function. **)** ###

-bash-4.2$ python3
    Python 3.6.8 (default, Apr 25 2019, 21:02:35)
    [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    
    >>> import subprocess
    >>> subprocess.call('ls -la', shell=True)
    total 20
    drwxr-xr-x 4 sradhakr sw 4096 Oct 17 15:42 .
    drwxr-xr-x 8 sradhakr sw 8192 Oct  8 13:40 ..
    -rw-r--r-- 1 sradhakr sw    9 Oct 17 15:42 output.txt
    drwxr-xr-x 4 sradhakr sw 4096 Oct  1 17:37 python_samples
    drwxr-xr-x 5 sradhakr sw 4096 Sep 29 19:53 venv
    >>>

Using **shell=True**, comes with a security risk if the command comes from an untrusted source. For example, using the user input, if we receive a command such as **rm –rf/** is potentially a dangerous command for a file system.

如果命令来自不受信任的来源，则使用**shell = True**会带来安全风险。 例如，使用用户输入，如果我们收到诸如**rm –rf /之类的**命令，则对于文件系统可能是危险的命令。

In order to capture the command output in a string, use **subprocess.check\_output()**,

为了捕获字符串中的命令输出，请使用**subprocess.check\_output()** ，

import subprocess
    
    try:
        output = subprocess.check_output(input('enter command >> '), shell=True)
        print(output)
    except subprocess.CalledProcessError as e:
        print('exception with returncode: {}, command: {}, output = {}'.format(e.returncode, e.cmd, e.output))

**Output**

**输出量**

enter command >> whoami
    b'user\n'

### 从命令退出代码 **(**Exit code from the command**)** ###

The **exit command** determines the success or failure of the processing of the command. The return value of the **call()** is the exit code and it determines the result of the processing of the command.

**exit命令**确定**命令**处理的成功或失败。 **call()**的返回值是退出代码，它确定命令处理的结果。

Python 3.6.8 (default, Apr 25 2019, 21:02:35)
    [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    
    >>> import subprocess
    >>> print("return code {}".format(subprocess.call('ls -la', shell=True)))
    total 20
    drwxr-xr-x 4 sradhakr sw 4096 Oct 17 15:42 .
    drwxr-xr-x 8 sradhakr sw 8192 Oct  8 13:40 ..
    -rw-r--r-- 1 sradhakr sw    9 Oct 17 15:42 output.txt
    drwxr-xr-x 4 sradhakr sw 4096 Oct  1 17:37 python_samples
    drwxr-xr-x 5 sradhakr sw 4096 Sep 29 19:53 venv
    return code 0

In order to get additional information about the processing of the external command there is an additional method called **subprocess.check\_call()**.

为了获得有关外部命令处理的附加信息，还有一个名为**subprocess.check\_call()**的附加方法。

import subprocess
    try:
        print(subprocess.check_call(['cat','random.txt']))
    except subprocess.CalledProcessError as e:
         print('exception: returncode: {}, command: {}'.format(e.returncode, e.cmd))

**Output**

**输出量**

cat: random.txt: No such file or directory
    exception: returncode: 1, command: ['cat', 'random.txt']

> 翻译自: [https://www.includehelp.com/python/how-to-call-an-external-command.aspx][https_www.includehelp.com_python_how-to-call-an-external-command.aspx]

在python中调用命令行

[https_www.includehelp.com_python_how-to-call-an-external-command.aspx]: https://www.includehelp.com/python/how-to-call-an-external-command.aspx