Unexpected heading and trailing symbols in logfile's string

edit

I'm wondering why are these symbols appended to the string in log file [..]

They are ANSI escape codes, used by ROS logging to add colours and font weights (such as boldface) to logging lines.

When output is set to "screen" no extra symbols is shown.

That is because the terminal driver knows how to interprete these sequences and uses them to set font properties for the logging lines.

is there any chance to get rid of the(m)?

If you just want to view a file with embedded escape sequences, you can use less -r /path/to/your/file.log. less will interprete the escape codes then and show you the text as it was printed to the console.

To actually remove them from the file seems to be not so straightforward (see here).

Some options however:

• how can I strip escape sequences from a text file?: uses sed
• Remove color codes (special characters) with sed: also sed
• Remove ANSI codes when storing script output: doesn't really remove them, but tries to avoid them being added in the first place by forcing the terminal to report it doesn't support colours.