Command Line Tricks: How To Identify Date and Time of a Unix Command Execution

Question: How do I find out what time I executed a command previously on Unix OS? The history command doesn’t display timestamp.

Answer: Set HISTTIMEFORMAT as shown below. Please note that there is a space before the last single-quotes.

$ export HISTTIMEFORMAT='%F %T '

After the above setting, history command will display timestamp in front of all commands. You can also search the history as shown below.

$ history | less
search for the required command

  351  2009-09-08 09:53:47 ls -lrt
  352  2009-09-08 09:53:49 cd ..
  353  2009-09-08 09:55:39 wget -mk -w 20 -P top5-1 -N
  354  2009-09-08 10:00:04 gk
  355  2009-09-08 10:00:07 cd Bash/Wget/
  356  2009-09-08 10:00:07 ls
/wget

Note: For a full list of history command hacks, refer to: Mastering Linux command line history.

How to view the output in other time formats ?

To view all available date formats do the following.

$ man strftime

Based on the definition from strftime, following are few examples of date and time format that you can use in your history command.

To display AM / PM:

$ export HISTTIMEFORMAT='%F %r '

$ history
  351  2009-09-08 09:53:47 PM ls -lrt
  352  2009-09-08 09:53:49 PM cd ..

To display in dd-MON-YY time format:

$ export HISTTIMEFORMAT='%d-%b-%Y %r '

$ history
  351  08-Sep-2009 09:53:47 PM ls -lrt
  352  08-Sep-2009 09:53:49 PM cd ..

To display timezone:

$ export HISTTIMEFORMAT='%d-%b-%Y %r %Z'

$ history
  351  08-Sep-2009 09:53:47 PM PDT ls -lrt
  352  08-Sep-2009 09:53:49 PM PDT cd ..

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