Putty Log filename

Automatically logging SSH and serial sessions in PuTTY is essential for auditing, troubleshooting, and compliance. Instead of manually specifying a static filename or overwriting previous session captures, PuTTY supports built-in wildcard variables to dynamically generate unique, structured log paths based on target hosts, timestamps, and connection ports.

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Configuring Dynamic Log File Names

In PuTTY, navigate to Session > Logging in the left sidebar. Under Session logging, select "All session output" (or "Printable output only"), then configure the Log file name field.

When defining your path, use the & parameter prefix to automatically inject real-time session metadata into the filename.

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Supported Substitution Variables

Variable	Replacement Description	Example Output
&H	Target Host Name / IP Address	web01.example.internal
&P	Destination Port Number	22
&Y	Current Year (4 digits)	2026
&M	Current Month (2 digits)	08
&D	Current Day of Month (2 digits)	31
&T	Current Time (6 digits: HHMMSS)	143015

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Practical Path Examples

1. Standard Host and Timestamp Template

To organize session captures by target server name and full timestamp, enter the following pattern in the Log file name box:

C:\puttylogs\&H_&Y-&M-&D_&T.log

PuTTY automatically resolves this into clean, chronological log files:

C:\puttylogs\srv-db01.internal_2026-08-31_125405.log
C:\puttylogs\192.168.1.10_2026-08-31_130522.log

2. Dedicated Port and Daily File Naming

If connecting to non-standard ports or consolidating daily sessions into one log per host:

C:\puttylogs\&H_port&P_&Y&M&D.log

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Best Practice: Saving to Default Settings

To ensure every future connection is logged automatically without setting this per profile:

1. Open PuTTY and go to Session > Logging.
2. Set the desired logging method and dynamic file path.
3. Select "Always append to the end of it" under What to do if the log file already exists.
4. Click back to Session in the left pane, click Default Settings, and hit Save.