Bash date/time arithmetic

Question

I have a little Bash script which suspends the computer after a given number of minutes. However, I'd like to extend it to tell me what the time will be when it will be suspended, so I can get a rough idea of how long time I have left so to speak.

#!/bin/sh
let SECS=$1*60
echo "Sleeping for" $1 "minutes, which is" $SECS "seconds."
sleep $SECS &&
pm-suspend

The only argument to the script will be how many minutes from now the computer should be suspended. All I want to add to this script is basically an echo saying e.g. "Sleeping until HH:nn:ss!". Any ideas?

score 10 · Accepted Answer · answered Jun 09 '09 at 01:41

10

Found out how.

echo "The computer will be suspended at" $(date --date "now $1 minutes")

answered Jun 09 '09 at 01:41

Deniz Dogan

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admit it; you just asked this question so you could answer it and get the "self-learner" badge. :-) – glenra Jun 09 '09 at 02:44
Haha, no, seriously. I think I already have that badge anyways? No, I didn't. No, but I just didn't think it was this easy. – Deniz Dogan Jun 10 '09 at 10:57
The first pair of quotes is superfluous – darw Dec 27 '20 at 21:00
Shorter: `date --date "$1 minutes" +'The computer will be suspended at %c'` – darw Dec 27 '20 at 21:18

score 3 · Answer 2 · answered Nov 01 '09 at 19:01

3

On BSD-derived systems, you'd use

date -r $(( $(date "+%s") + $1 * 60 ))

i.e. get the current date in seconds, add the number of minutes, and feed it back to date.
Yeah, it's slightly less elegant.

answered Nov 01 '09 at 19:01

Michiel Buddingh

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@Chris I think formatting screwed you up there... there's no ending ` – lmat - Reinstate Monica Nov 15 '13 at 15:46
deleted my back-ticks comment since it's part of an answer below – Chris Nov 16 '13 at 17:05
more interesting to me is the use of the $ syntax to execute the date function instead of single back quotes. – Chris Nov 16 '13 at 17:06

score 1 · Answer 3 · edited Nov 16 '13 at 17:06

1

on linux

SECS=`date "+$s"`
SECS=$(( SECS + $1 * 60 ))
date --date $SECS

edited Nov 16 '13 at 17:06

gniourf_gniourf

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answered Jul 24 '13 at 03:29

Chris

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I think formatting screwed you up there... there's no ending ` – lmat - Reinstate Monica Nov 15 '13 at 15:46
I added backslashes to escape the backticks. fixed. – Chris Nov 16 '13 at 17:03

Bash date/time arithmetic

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