Learn Linux Shell Scripting - Fundamentals of Bash 4.4

The history command

A very powerful and cool command in Bash is history. Simply put, by default, Bash will store a history of all the commands you type. These are saved up to a certain threshold, and for our Ubuntu 18.04 installation this is 1,000 commands in memory and 2,000 commands on disk. Every time you do a clean exit/logout of your terminal, Bash will write the command history from memory to disk, taking both limits into account.

Before we dive (a little) deeper, let's take a look at our personal history for the reader user:

reader@ubuntu:~$ history 1013  date 1014  at 11:49 << wall "Hi" 1015  at 11:49 <<< wall "Hi" 1016  echo 'wall "Hi"' | at 11:49<SNIPPED> 1998  array=("This" "is" "an" "array") 1999  echo ${array[0]} 2000 echo ${array[1]} ...