What was that Linux command I issued yesterday about tea time?

With the Linux history command you can display the commands that have been issued. 

For example

history |grep route

Displays all the commands (in the history file) containing the word route.

It displays output like

 15  traceroute 2001:db8:8::9
 16  sudo ip -6 route add fd00::6:1:1/128 dev tap2
 18  sudo ip -6 route add 2001:db8:8::9/128 dev tap2
 30  grep route /home/zPDT/*.sh 
 40  ip -6 route 

This page has some good examples of history usage

• !?route displays the lines in the history file which include route
• !5 executes the 5th line in the history file

I wanted to find the command I issued yesterday around 4PM. You can display the dates and times of the history records.

Setting the environment variable

HISTTIMEFORMAT="%d/%m/%y %T "
history |grep route

gave me

  30  12/02/24 07:58:50 grep route /home/zPDT/*.sh 
  40  12/02/24 07:58:50 ip -6 route 
  46  12/02/24 07:58:50 traceroute 2001:db8:8::9 
  74  12/02/24 07:58:50 traceroute 2001:db8::3 

Using

HISTTIMEFORMAT="%T "
history |grep route

gave just the time of day.

30 07:58:50 grep route /home/zPDT/*.sh
40 07:58:50 ip -6 route
46 07:58:50 traceroute 2001:db8:8::9
74 07:58:50 traceroute 2001:db8::3
86 07:58:50 traceroute 192.168.1.74

To keep this, you should put

export HISTTIMEFORMAT=”%T “

in the .bashrc file

You can also set in .bashrc

• export HISTSIZE=50 The maximum number of entries displayed with the history list.
• export HISTFILESIZE=5000 The maximum number of entries in the .bash_history file.