bash Cookbook

Disconnecting Inactive Sessions

Problem

You’d like to be able to automatically log out inactive users, especially root.

Solution

Set the $TMOUT environment variable in /etc/bashrc or ~/.bashrc to the number of seconds of inactivity before ending the session. In interactive mode, once a prompt is issued, if the user does not enter a command in $TMOUT seconds, bash will exit.

Discussion

$TMOUT is also used in the read built-in and the select command in scripts.

Don’t forget to set this as a read-only variable in a system-level file such as /etc/profile or /etc/bashrc to which users have no write access if you don’t want them to be able to change it.

declare -r TMOUT=3600

# Or:
readonly TMOUT=3600

Warning

Since the user has control over their own environment, you cannot totally rely on $TMOUT, even if you set it as read-only, since the user could just run a different shell. Think of it as a helpful reminder to cooperative users, especially knowledgeable and interrupt-driven system administrators who may get distracted (constantly).

See Also

• Creating Self-Contained, Portable RC Files