155. Subprocess Management with subprocess

Here are 10 Python snippets demonstrating subprocess management with the subprocess module for running system commands and interacting with external processes. Each snippet is separated by a delimiter.

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Snippet 1: Running a Simple Command

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import subprocess

result = subprocess.run(['echo', 'Hello, World!'], capture_output=True, text=True)
print("Output:", result.stdout)

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Snippet 2: Capturing Errors

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import subprocess

result = subprocess.run(['ls', 'non_existent_directory'], capture_output=True, text=True)
print("Error:", result.stderr)

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Snippet 3: Checking Command Success

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import subprocess

result = subprocess.run(['ls'], capture_output=True, text=True)
if result.returncode == 0:
    print("Command succeeded")
else:
    print("Command failed with return code:", result.returncode)

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Snippet 4: Running a Shell Command

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import subprocess

result = subprocess.run('echo $HOME', shell=True, capture_output=True, text=True)
print("Home Directory:", result.stdout.strip())

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Snippet 5: Redirecting Output to a File

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import subprocess

with open('output.txt', 'w') as file:
    subprocess.run(['echo', 'Writing to a file'], stdout=file)
print("Output written to 'output.txt'")

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Snippet 6: Passing Input to a Command

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import subprocess

result = subprocess.run(['cat'], input="This is input text\n", text=True, capture_output=True)
print("Command Output:", result.stdout)

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Snippet 7: Running a Command Without Waiting for Completion

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import subprocess

process = subprocess.Popen(['sleep', '5'])
print("Process started with PID:", process.pid)

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Snippet 8: Communicating with a Process

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import subprocess

process = subprocess.Popen(['cat'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, text=True)
stdout, _ = process.communicate("This is sent to stdin")
print("Output from the process:", stdout)

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Snippet 9: Running Multiple Commands Sequentially

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import subprocess

subprocess.run(['echo', 'First Command'])
subprocess.run(['echo', 'Second Command'])

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Snippet 10: Using subprocess.PIPE for Real-Time Output

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import subprocess

process = subprocess.Popen(['ping', '-c', '4', 'google.com'], stdout=subprocess.PIPE, text=True)
for line in process.stdout:
    print(line.strip())

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