Log support for console apps that use \r to update line (e.g.: progress bars)

[fishnux]

Log support for console apps that use \r to update line (e.g.: progress bars)

Some console apps use \r to move the cursor to the beginning of the current line in order to update progress (e.g.: progress bar). In Dagu, a \r doesn't work, and a new line is printed instead, so the log file is spammed with progress updates.

In order to fix this in Dagu, there would be a need of a buffer to hold the last printed line, so it can be manipulated (with \r) before being written to a file. The web interface should show this last line, even if not written to the log file already (so we can see the progress).

Example script to be used for testing:

#!/usr/bin/env python3
import time
import sys

def simulate_progress_bar(total_steps):
    bar_size = 20  # The size of the progress bar in characters
    for step in range(total_steps + 1):
        progress = step / total_steps  # Calculate the progress as a fraction
        completed_chars = int(bar_size * progress)  # Calculate how many characters to fill based on progress
        # Create the progress bar string: [=====>        ]
        bar = '[' + '=' * completed_chars + ' ' * (bar_size - completed_chars) + ']'
        # Use \r to overwrite the current line with the updated progress bar and percentage
        sys.stdout.write('\r' + bar + f' {progress:.1%}')
        sys.stdout.flush()  # Flush the output to ensure it's immediately visible
        time.sleep(0.1)  # Simulate a process delay for demonstration purposes
    sys.stdout.write('\n')  # Print a newline when the progress is complete

if __name__ == "__main__":
    total_steps = 50  # Total number of steps for the progress
    simulate_progress_bar(total_steps)

[fishnux]

This is more complex than I thought. Some apps won't output progress bars if the terminal is not a "TTY". In some cases progress bars are useful to be logged as they're the only way to keep track of a long running task, but not more than once a second (and in reality a progress bar may be updated many times per second, potentially spamming the log file [like I mentioned in the first post])