Timestamp bash_history with every command

When working on Linux it is often very helpful to review the commands that you have entered. For example, you may want to paste some of the commands into a script or may want to recreate the steps to solve the problem you were working on.

Here is how I do it:

## Modify History for Current Session
# Add Timestamp to .bash_history
HISTTIMEFORMAT="%d/%m/%y %T "
# Write Current History to .bash_history
history -a
# Update .bash_history with every command
export PROMPT_COMMAND='history -a'

## Add to .bash_profile to make changes permanent
echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> $HOME/.bashrc
echo "export PROMPT_COMMAND='history -a'" >> $HOME/.bashrc

## Save the last 10,000 lines to disk and keep 5000 lines in memory
cat $HOME/.bashrc | sed 's/#\?\(HISTSIZE\s*=\s*\).*$/\15000/' | \
    sed 's/#\?\(HISTFILESIZE\s*=\s*\).*$/\110000/' > temp.txt
mv -f temp.txt $HOME/.bashrc
source ~/.bashrc

See also https://www.digitalocean.com/community/tutorials/how-to-use-bash-history-commands-and-expansions-on-a-linux-vps

NOTE: if you want to display the recent history without timestamps, just use fc -ln

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