Is there any way to convert a putty "All session output" log, with control characters, to a more human readable "Printable output" log?

Question

We had a contractor in-house to help with some configuration of a product and we're trying to look through the putty logs he set up for us, but instead of using "printable output" he used "all session output" which includes every keystroke including "BS", etc. making the logs very difficult to read as he had many, many typos. ie:

[ESC]]0;root@host:~[BEL][root@host ~]# itm,cm[BS][BS][ESC][K[BS][ESC][Kcmd agent starp[BS]t

Is there some way to strip these control characters out, intelligently, so that the end result is a human readable file much like what you'd see in "printable output" format?

Thank you for the below suggestion. Our major painpoint is the [BS] control characters, which would turn this:

ls -pg[BS][BS]al P[BS]| greu[BS]p dr

into:

ls -al | grep dr

Any idea how that could be accomplished?

Answer 1

Enable a very large scrollback in putty, cat the log file, and copy and paste the result into a new file.

Answer 2

While not perfect, this sed filter will give you a starting point.

sed -r 's/(\[[A-Z]+\]?|\]0;)//g' escapes.log > noescapes.log

If I pipe your sample through that filter, I get:

root@host:~[root@host ~]# itm,cmcmd agent starpt

A solution that relies on a command/script to parse out the actual terminal codes would be more elegant, this is more of a "quick fix".

Regex breakdown for those who are trying to learn them:

• outer parenthesis for purposes of alternation (the | character is OR)
• \[ and \] are escaped square brackets, so that they won't be interpreted as a character class.
• [ ] contain a character class. [A-Z] is a class for matching any uppercase letter.
• + indicates to match "one or more of the previous atom". The previous atom was the character class, so "one or more uppercase letters".
• ? indicates that the previous atom is optional. In this case, the optional atom is \].
• Combined meaning at this point: "an occurrence of one or more uppercase characters preceded by a literal [, optionally suffixed by a literal ]"
• The | character is the start of the OR.
• \]0; matches 'a literal ] suffixed by 0;`.

The replacement string is empty, so they get removed. /g tells sed to not stop at the first match.