python run shell command example

Use subprocess.run() to safely execute shell commands and capture output. It is recommended to pass parameters in lists to avoid injection risks; 2. When shell characteristics are required, you can set shell=True, but beware of command injection; 3. Use subprocess.Popen to realize real-time output processing; 4. Set check=True to throw exceptions when the command fails; 5. In simple scenarios, you can directly call to get output; subprocess.run() should be given priority in daily use to avoid using os.system() or deprecated modules. The above methods override the core usage of executing shell commands in Python.

There are many ways to execute shell commands in Python, and the most commonly used is to use the subprocess module. Here are some practical examples showing how to run shell commands in Python.

1. Use subprocess.run() (recommended method)

This is the recommended method in Python 3.5, which is simple, safe and powerful.

 import subprocess

# Run a simple shell command result = subprocess.run(['ls', '-l'], capture_output=True, text=True)

# Output command return code, standard output and error print("return code:", result.returncode)
print("Output:\n", result.stdout)
print("Error:\n", result.stderr)

? Note: ['ls', '-l'] is to pass parameters in a list form to avoid the risk of shell injection. If shell characteristics are required (such as wildcards, pipes), add shell=True .

2. Run commands with shell characteristics (using shell=True )

 import subprocess

result = subprocess.run('echo $HOME | xargs ls', shell=True, capture_output=True, text=True)
print("Output:\n", result.stdout)

⚠️ Warning: Be careful when using shell=True to prevent command injection.

3. Real-time output command execution process (not waiting for completion)

If you want to see real-time output of commands (such as long-running scripts):

 import subprocess

# Real-time printout process = subprocess.Popen(['ping', '-c', '5', 'google.com'], stdout=subprocess.PIPE, text=True)

for line in process.stdout:
    print("Output:", line.strip())

process.wait() # Wait for completion print("Complete, return code:", process.returncode)

4. Execute the command and get the return value to determine whether it is successful

 import subprocess

try:
    subprocess.run(['python', '--version'], check=True, capture_output=True, text=True)
    print("Command execution succeeded")
except subprocess.CalledProcessError as e:
    print("Command execution failed:", e)

• check=True will throw an exception when the command returns to a non-zero state.

5. Quickly execute and get output (suitable for simple scenarios)

If you just want to get the command output quickly, you can use:

 import subprocess

# Concise writing output = subprocess.run('date', shell=True, capture_output=True, text=True).stdout.strip()
print("Current time:", output)

Common uses examples

• Check if the file exists:

   result = subprocess.run(['test', '-f', 'config.txt'], capture_output=True)
  if result.returncode == 0:
      print("File exists")

• Execute the Git command:

   result = subprocess.run(['git', 'rev-parse', '--abbrev-ref', 'HEAD'], capture_output=True, text=True)
  print("Current branch:", result.stdout.strip())

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  Basically these common methods. It is recommended to use subprocess.run() on a daily basis to avoid using deprecated os.system() or commands modules.

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