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Six methods of invoking system commands by Python

Os or subprocess module is generally used to call system commands in Python. Here are the six most commonly used methods of calling system commands in Python.

1. Os.system ()

This function returns the return value of the result of the execution of the command, and the system () function performs the following three steps during execution:

1. Fork a child process

2. Call the exec function in the child process to execute the command

3. Call wait (blocking) in the parent process to wait for the child process to finish.

Returning 0 indicates successful execution of the command, while others indicates failure.

Usage:

Os.system ("command")

2. Os.popen ()

This call method is achieved through the pipeline. The function returns the object of file read, and the output of the execution can be seen by reading read, readlines and other operations.

Usage:

Os.popen ("command")

3. Subprocess.Popen ()

Subprocess module is recommended to replace some old modules and functions, such as os.system, os.spawn, os.popen, etc.

The purpose of the subprocess module is to fork and communicate with a new process. The most common is to define the class Popen. Using Popen, you can create a process and interact with it in a complex way.

Usage:

Child = subprocess.Popen (["cmd", "arg1"...])

4. Subprocess.call ()

Executes the specified command and returns the command execution status, which is similar to os.system (cmd).

Usage:

Subprocess.call ("command")

5. Subprocess.run ()

The new function in Python 3.5 executes the specified command and waits for the command execution to return an instance of the CompletedProcess class that contains the execution result.

Usage:

Subprocess.run (args, *, stdin=None, input=None, stdout=None, stderr=None, shell=False, timeout=None, check=False, universal_newlines=False)

6. Subprocess.getstatusoutput ()

Executes the cmd command and returns a tuple (command execution status, command execution result output), which functions similar to commands.getstatusoutput ().

Usage:

Subprocess.getstatusoutput ("command")

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