kensaii kensaii - 2 months ago 6
Bash Question

Calculate 15 minutes ago in shell

I have a time-stamp like 7:00:00, which means 7am.

I would like to write a short command that returns 06:45:00, or simply 06:45, preferably using date command so that I can avoid long shell script. Do you have any elegant solution?

Answer

With GNU date, use 7:00:00 AM - 15 minutes as d (--date) string :

% date -d '7:00:00 AM - 15 minutes' '+%H:%M'
06:45

+%H:%M sets the output format as HH:MM.

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