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subprocess.py

Easily run a subprocess and capture the result.

The subprocess_command function wraps Python's subprocess.run() with sensible defaults to run a command and to control how results and errors are reported.

Example Usage

Assemble a command-line string.

shell_escape() escapes a path string for safe use in shell commands.

python

path = "/path/to/somewhere with spaces"
escaped_path = shell_escape(path)
cmd = f"ls {escaped_path}"
print(cmd)  # ls "/path/to/somewhere with spaces"

Run a shell command.

python

output = subprocess_command("echo Hello, World!")
print(output)  # Hello, World!

Handle errors.

subprocess_command() does not raise CalledProcessError by default. On a failed shell command, the function returns None. Output from the shell's stderr is logged to the Python process's stderr.

python

cmd = f"ls {shell_escape("/path/to/somewhere with spaces")}"
output = subprocess_command(cmd)
print(output)

stdout

None

stderr

Command 'ls "/path/to/somewhere with spaces"' returned non-zero exit status 1.
ls: /path/to/somewhere with spaces: No such file or directory

subprocess_command() Description

Input is a command-line string. Output, if all went well, is the standard output of the command as a UTF-8 string.

Parameters

  • cmd (str): The shell command to run.
  • report_process_error (bool): Logs errors if the subprocess command fails.
  • report_std_error (bool): Logs standard error output.
  • raise_std_error (bool): Raises a CalledProcessError if the subprocess command fails.
  • strip_output (bool): Strips leading and trailing whitespace from the output.
  • **kwargs: Additional arguments to pass to subprocess.run.

Returns

  • Optional[str]: The standard output of the command, or None if an error occurs.