Python history command has no output

I'm trying to get the output of the history command in python, but it returns nothing. When I run it in the terminal it returns my last commands. I'm using Mac OS.

import subprocess

command = 'history'

# Execute the command using a shell
result = subprocess.run(command, shell=True, capture_output=True, text=True)

# Check the result
if result.returncode == 0:
    print("Command executed successfully!")
    print("Output:")
    print(result.stdout)
else:
    print("Error executing command:")
    print(result.stderr)

Output:

Command executed successfully!
Output:

Solution

Here's a simple explanation of what I know about it:

When you run the history command via subprocess in Python, it typically returns nothing because history is not an actual command like ls or cat, but rather a shell builtin that's available in your terminal (like bash or zsh). This means history works within the context of a shell session to list the commands you've executed in that session, and it relies on the environment of the shell to function.

When you execute subprocess.run with shell=True, it starts a new shell session for that command, which doesn't have the same command history as your interactive terminal session. Therefore, the history command doesn't return anything because, from the perspective of that new shell session, no commands have been executed.

If you want to access the command history in a script, you might consider reading the history file directly. For bash, this is typically ~/.bash_history, and for zsh, it's ~/.zsh_history. You can read this file from Python to get the command history. Here's how you could do it for bash:

history_file = '~/.bash_history'

# Expand the path to the user's home directory
full_path = os.path.expanduser(history_file)

try:
    with open(full_path, 'r') as file:
        history = file.readlines()
    print("Command executed successfully!")
    print("Output:")
    for command in history:
        print(command.strip())
except Exception as e:
    print(f"Error reading history file: {e}")

Adjust the history_file variable if you're using a different shell. Thanks