The function of 'Ctrl-d'(^D) key is to exit the shell. If IGNOREEOF variable does not exist in your shell a single ^D will exit from the shell (this is the default behavior).
What is this $IGNOREEOF ?
It controls the action of the shell on receipt of an EOF character as the sole input.
If set, the value is the number of consecutive EOF characters typed as the first characters on an input line before bash exits.
If the variable exists but does not have a numeric value, or has no value, the default value is 10.
Now if you set the following:
This will prevent the shell to exit with a single press of 'Ctrl d' and will require two consecutive 'Ctrl d' (^D) to exit the session. You can also add it to your '~/.bashrc'.
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