•‘Printable output’. In this mode, a log file will be created and written to, but only printable text will be saved into it. The various terminal control codes that are typically sent down an interactive session alongside the printable text will be omitted. This might be a useful mode if you want to read a log file in a text editor and hope to be able to make sense of it.
•‘All session output’. In this mode, everything sent by the server into your terminal session is logged. If you view the log file in a text editor, therefore, you may well find it full of strange control characters. This is a particularly useful mode if you are experiencing problems with PuTTY's terminal handling: you can record everything that went to the terminal, so that someone else can replay the session later in slow motion and watch to see what went wrong.
•‘SSH packets’. In this mode (which is only used by SSH connections), the SSH message packets sent over the encrypted connection are written to the log file (as well as Event Log entries). You might need this to debug a network-level problem, or more likely to send to the PuTTY authors as part of a bug report. BE WARNED that if you log in using a password, the password can appear in the log file; see
section 4.2.4
for options that may help to remove sensitive material from the log
file before you send it to anyone else.
•‘SSH packets and raw data’. In this mode, as well as the decrypted packets (as in the previous mode), the raw (encrypted, compressed, etc) packets are also logged. This could be useful to diagnose corruption in transit. (The same caveats as the previous mode apply, of course.)
Note that the non-SSH logging options (‘Printable output’ and ‘All session output’) only work with PuTTY proper; in programs without terminal emulation (such as Plink), they will have no effect, even if enabled via saved settings.
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4.2.1 ‘Log file name’
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4.2.2 ‘What to do if the log file already exists’
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4.2.3 ‘Flush log file frequently’
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4.2.4 Options specific to SSH packet logging
o
4.2.4.1 ‘Omit known password fields’
o
4.2.4.2 ‘Omit session data’
4.2.1 ‘Log file name’
In this edit box you enter the name of the file you want to log the session to. The ‘Browse’ button will let you look around your file system to find the right place to put the file; or if you already know exactly where you want it to go, you can just type a pathname into the edit box.
There are a few special features in this box. If you use the & character in the file name box, PuTTY will insert details of the current session in the name of the file it actually opens. The precise replacements it will do are:
•&Y will be replaced by the current year, as four digits.
•&M will be replaced by the current month, as two digits.
•&D will be replaced by the current day of the month, as two digits.
•&T will be replaced by the current time, as six digits (HHMMSS) with no punctuation.
•&H will be replaced by the host name you are connecting to.
•&P will be replaced by the port number you are connecting to on the target host.
For example, if you enter the host name c:\puttylogs\log-&h-&y&m&d-&t.dat, you will end up with files looking like
log-server1.example.com-20010528-110859.dat
log-unixbox.somewhere.org-20010611-221001.dat
4.2.2 ‘What to do if the log file already exists’
This control allows you to specify what PuTTY should do if it tries to start writing to a log file and it finds the file already exists. You might want to automatically destroy the existing log file and start a new one with the same name. Alternatively, you might want to open the existing log file and add data to the end of it. Finally (the default option), you might not want to have any automatic behaviour, but to ask the user every time the problem comes up.
4.2.3 ‘Flush log file frequently’
This option allows you to control how frequently logged data is flushed to disc. By default, PuTTY will flush data as soon as it is displayed, so that if you view the log file while a session is still open, it will be up to date; and if the client system crashes, there's a greater chance that the data will be preserved.