The proper way to achieve this is to set TMOUT variable to the number of seconds to wait for an user input using global profile.
Execute following commands to define 120 seconds timeout.
$ cat << EOF | sudo tee /etc/profile.d/tmout.sh
# Execute only outside of X-terminal
[ -z "\$DISPLAY" ] || return 0
export TMOUT=120
EOF
$ sudo chmod 644 /etc/profile.d/tmout.sh
Changes will take place after user re-login. Bash will simply terminate after timeout.
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