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Using the date program, how can I calculate the number of seconds since midnight?

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date "+(%H*60+%M)*60+%S" | bc – groxxda Jul 25 '14 at 13:42
echo $(($(date '+(%H*60+%M)*60+%S'))) – groxxda Jul 25 '14 at 13:59
up vote 10 down vote accepted

To avoid race conditions, still assuming GNU date:

eval "$(date +'today=%F now=%s')"
midnight=$(date -d "$today 0" +%s)
echo "$((now - midnight))"

With zsh, you can do it internally:

zmodload zsh/datetime
strftime -s today %F $now
strftime -rs midnight %F $today
echo $((now - midnight))

Portably, in timezones where there's no daylight saving switch, you could do:

set -- $(date +%T)
echo "$(($1 * 3600 + $2 * 60 + $3))"
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Very clever and good use of eval – Ulrich Dangel Jul 25 '14 at 13:14

Based on bash, get current time in milliseconds since midnight, on a GNU system, it can be done like this:

$ now=$(date '+%s')
$ midnight=$(date -d 'today 00:00:00' '+%s')
$ echo $(( now - midnight ))
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You want to make sure you don't do that at 23:59:59 – Stéphane Chazelas Jul 25 '14 at 13:02
And to convert back: date -d @$seconds – choroba Jul 25 '14 at 13:05

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