Sleep until a specific time/date
BashSleepWaitBash Problem Overview
I want my bash script to sleep until a specific time. So, I want a command like "sleep" which takes no interval but an end time and sleeps until then.
The "at"-daemon is not a solution, as I need to block a running script until a certain date/time.
Is there such a command?
Bash Solutions
Solution 1 - Bash
As mentioned by Outlaw Programmer, I think the solution is just to sleep for the correct number of seconds.
To do this in bash, do the following:
current_epoch=$(date +%s)
target_epoch=$(date -d '01/01/2010 12:00' +%s)
sleep_seconds=$(( $target_epoch - $current_epoch ))
sleep $sleep_seconds
To add precision down to nanoseconds (effectively more around milliseconds) use e.g. this syntax:
current_epoch=$(date +%s.%N)
target_epoch=$(date -d "20:25:00.12345" +%s.%N)
sleep_seconds=$(echo "$target_epoch - $current_epoch"|bc)
sleep $sleep_seconds
Note that macOS / OS X does not support precision below seconds, you would need to use coreutils from brew instead → see these instructions
Solution 2 - Bash
Sample edited: Wed Apr 22 2020, something between 10:30 and 10h:55
(Important for reading samples)
General method (Avoid useless forks!)
As this question was asked 4 years ago, this first part concerns old bash versions:
(Nota: this method use date -f wich is no POSIX and don't work under MacOS! If under Mac, goto my pure [tag:bash] function)
In order to reduce forks, instead of running date two times, I prefer to use this:
Simple starting sample
sleep $(( $(date -f - +%s- <<< "tomorrow 21:30"$'\nnow') 0 ))
where tomorrow 21:30 could be replaced by any kind of date and format recognized by date, in the future .
if read -rp "Sleep until: " targetTime ;then
sleep $(( $(date -f - +%s- <<< "$targetTime"$'\nnow') 0 ))
fi
With high precision (nanosec)
Nearly same:
sleep $(bc <<<s$(date -f - +'t=%s.%N;' <<<$'07:00 tomorrow\nnow')'st-t')
Reaching next time
For reaching next HH:MM meaning today if possible, tomorrow if too late:
sleep $((($(date -f - +%s- <<<$'21:30 tomorrow\nnow')0)%86400))
This works under [tag:bash], [tag:ksh] and other modern shells, but you have to use:
sleep $(( ( $(printf 'tomorrow 21:30\nnow\n' | date -f - +%s-)0 )%86400 ))
under lighter shells like [tag:ash] or [tag:dash].
Pure [tag:bash] way, no fork!!
Tested under MacOS!
I wrote one two little functions: sleepUntil and sleepUntilHires
Syntax:
sleepUntil [-q] <HH[:MM[:SS]]> [more days]
-q Quiet: don't print sleep computed argument
HH Hours (minimal required argument)
MM Minutes (00 if not set)
SS Seconds (00 if not set)
more days multiplied by 86400 (0 by default)
As new versions of bash do offer a printf option to retrieve date, for this new way to sleep until HH:MM whithout using date or any other fork, I've build a little [tag:bash] function. Here it is:
sleepUntil() { # args [-q] <HH[:MM[:SS]]> [more days]
local slp tzoff now quiet=false
[ "$1" = "-q" ] && shift && quiet=true
local -a hms=(${1//:/ })
printf -v now '%(%s)T' -1
printf -v tzoff '%(%z)T\n' $now
tzoff=$((0${tzoff:0:1}(3600*${tzoff:1:2}+60*${tzoff:3:2})))
slp=$((
( 86400+(now-now%86400) + 10#$hms*3600 + 10#${hms[1]}*60 +
${hms[2]}-tzoff-now ) %86400 + ${2:-0}*86400
))
$quiet || printf 'sleep %ss, -> %(%c)T\n' $slp $((now+slp))
sleep $slp
}
Then:
sleepUntil 10:37 ; date +"Now, it is: %T"
sleep 49s, -> Wed Apr 22 10:37:00 2020
Now, it is: 10:37:00
sleepUntil -q 10:37:44 ; date +"Now, it is: %T"
Now, it is: 10:37:44
sleepUntil 10:50 1 ; date +"Now, it is: %T"
sleep 86675s, -> Thu Apr 23 10:50:00 2020
^C
If target is before this will sleep until tomorrow:
sleepUntil 10:30 ; date +"Now, it is: %T"
sleep 85417s, -> Thu Apr 23 10:30:00 2020
^C
sleepUntil 10:30 1 ; date +"Now, it is: %T"
sleep 171825s, -> Fri Apr 24 10:30:00 2020
^C
HiRes time with [tag:bash] under GNU/Linux
Recent [tag:bash], from version 5.0 add new $EPOCHREALTIME variable with microseconds. From this there is a sleepUntilHires function.
sleepUntilHires () { # args [-q] <HH[:MM[:SS]]> [more days]
local slp tzoff now quiet=false musec musleep;
[ "$1" = "-q" ] && shift && quiet=true;
local -a hms=(${1//:/ });
printf -v now '%(%s)T' -1;
IFS=. read now musec <<< $EPOCHREALTIME;
musleep=$[2000000-10#$musec];
printf -v tzoff '%(%z)T\n' $now;
tzoff=$((0${tzoff:0:1}(3600*${tzoff:1:2}+60*${tzoff:3:2})));
slp=$(((( 86400 + ( now - now%86400 ) +
10#$hms*3600+10#${hms[1]}*60+10#${hms[2]} -
tzoff - now - 1
) % 86400 ) + ${2:-0} * 86400
)).${musleep:1};
$quiet || printf 'sleep %ss, -> %(%c)T\n' $slp $((now+${slp%.*}+1));
read -t $slp foo
}
Please note: this use read -t wich is built-in, instead of sleep. Unfortunely, this won't work when running in background, without real TTY. Feel free to replace read -t by sleep if you
plan to run this in background scripts... (But for background process, consider using cron and/or at instead of all this)
Skip next paragraph for tests and warning about $ËPOCHSECONDS!
Older method using /proc/timer_list, avoided to normal user, by recent Kernel!!
Under Linux kernel, you will find a variables file named /proc/timer_list where you could read an offset and a now variable, in nanoseconds. So we may compute sleep time to reach the very top desired time.
(I wrote this to generate and track specific events on very big log files, containing thousand line for one second).
mapfile </proc/timer_list _timer_list
for ((_i=0;_i<${#_timer_list[@]};_i++));do
[[ ${_timer_list[_i]} =~ ^now ]] && TIMER_LIST_SKIP=$_i
[[ ${_timer_list[_i]} =~ offset:.*[1-9] ]] && \
TIMER_LIST_OFFSET=${_timer_list[_i]//[a-z.: ]} && \
break
done
unset _i _timer_list
readonly TIMER_LIST_OFFSET TIMER_LIST_SKIP
sleepUntilHires() {
local slp tzoff now quiet=false nsnow nsslp
[ "$1" = "-q" ] && shift && quiet=true
local hms=(${1//:/ })
mapfile -n 1 -s $TIMER_LIST_SKIP nsnow </proc/timer_list
printf -v now '%(%s)T' -1
printf -v tzoff '%(%z)T\n' $now
nsnow=$((${nsnow//[a-z ]}+TIMER_LIST_OFFSET))
nsslp=$((2000000000-10#${nsnow:${#nsnow}-9}))
tzoff=$((0${tzoff:0:1}(3600*${tzoff:1:2}+60*${tzoff:3:2})))
slp=$(( ( 86400 + ( now - now%86400 ) +
10#$hms*3600+10#${hms[1]}*60+${hms[2]} -
tzoff - now - 1
) % 86400)).${nsslp:1}
$quiet || printf 'sleep %ss, -> %(%c)T\n' $slp $((now+${slp%.*}+1))
sleep $slp
}
After defining two read-only variables, TIMER_LIST_OFFSET and TIMER_LIST_SKIP, the function will access very quickly the variable file /proc/timer_list for computing sleep time:
Little test function
tstSleepUntilHires () {
local now next last
printf -v next "%(%H:%M:%S)T" $((${EPOCHREALTIME%.*}+1))
sleepUntilHires $next
date -f - +%F-%T.%N < <(echo now;sleep .92;echo now)
printf -v next "%(%H:%M:%S)T" $((${EPOCHREALTIME%.*}+1))
sleepUntilHires $next
date +%F-%T.%N
}
May render something like:
sleep 0.244040s, -> Wed Apr 22 10:34:39 2020
2020-04-22-10:34:39.001685312
2020-04-22-10:34:39.922291769
sleep 0.077012s, -> Wed Apr 22 10:34:40 2020
2020-04-22-10:34:40.004264869
- At begin of next second,
- print time, then
- wait 0.92 seccond, then
- print time, then
- compute 0.07 seconds left, to next second
- sleep 0.07 seconds, then
- print time.
Care to not mix $EPOCHSECOND and $EPOCHREALTIME!
Read my warning about difference between $EPOCHSECOND and $EPOCHREALTIME
This function use $EPOCHREALTIME so don't use $EPOCHSECOND for establishing next second:
Sample issue: Trying to print time next rounded by 2 seconds:
for i in 1 2;do
printf -v nextH "%(%T)T" $(((EPOCHSECONDS/2)*2+2))
sleepUntilHires $nextH
IFS=. read now musec <<<$EPOCHREALTIME
printf "%(%c)T.%s\n" $now $musec
done
May produce:
sleep 0.587936s, -> Wed Apr 22 10:51:26 2020
Wed Apr 22 10:51:26 2020.000630
sleep 86399.998797s, -> Thu Apr 23 10:51:26 2020
^C
Solution 3 - Bash
Use sleep, but compute the time using date. You'll want to use date -d for this. For example, let's say you wanted to wait until next week:
expr `date -d "next week" +%s` - `date -d "now" +%s`
Just substitute "next week" with whatever date you'd like to wait for, then assign this expression to a value, and sleep for that many seconds:
startTime=$(date +%s)
endTime=$(date -d "next week" +%s)
timeToWait=$(($endTime- $startTime))
sleep $timeToWait
All done!
Solution 4 - Bash
Here is a simple Bash one-liner:
sleep $(expr $(date -d "03/21/2014 12:30" +%s) - $(date +%s))
Solution 5 - Bash
Here is a solution that does the job AND informs the user about how much time is remaining.
I use it almost everyday to run scripts during the night (using cygwin, as I couldn't get cron to work on windows)
Features
- Precise down to the second
- Detects system time changes and adapts
- Intelligent output telling how much time is left
- 24-hour input format
- returns true to be able to chain with
&&
Sample run
$ til 13:00 && date
1 hour and 18 minutes and 26 seconds left...
1 hour and 18 minutes left...
1 hour and 17 minutes left...
1 hour and 16 minutes left...
1 hour and 15 minutes left...
1 hour and 14 minutes left...
1 hour and 10 minutes left...
1 hour and 5 minutes left...
1 hour and 0 minutes left...
55 minutes left...
50 minutes left...
45 minutes left...
40 minutes left...
35 minutes left...
30 minutes left...
25 minutes left...
20 minutes left...
15 minutes left...
10 minutes left...
5 minutes left...
4 minutes left...
3 minutes left...
2 minutes left...
1 minute left...
Mon, May 18, 2015 1:00:00 PM
(The date at the end is not part of the function, but due to the && date)
Code
til(){
local hour mins target now left initial sleft correction m sec h hm hs ms ss showSeconds toSleep
showSeconds=true
[[ $1 =~ ([0-9][0-9]):([0-9][0-9]) ]] || { echo >&2 "USAGE: til HH:MM"; return 1; }
hour=${BASH_REMATCH[1]} mins=${BASH_REMATCH[2]}
target=$(date +%s -d "$hour:$mins") || return 1
now=$(date +%s)
(( target > now )) || target=$(date +%s -d "tomorrow $hour:$mins")
left=$((target - now))
initial=$left
while (( left > 0 )); do
if (( initial - left < 300 )) || (( left < 300 )) || [[ ${left: -2} == 00 ]]; then
# We enter this condition:
# - once every 5 minutes
# - every minute for 5 minutes after the start
# - every minute for 5 minutes before the end
# Here, we will print how much time is left, and re-synchronize the clock
hs= ms= ss=
m=$((left/60)) sec=$((left%60)) # minutes and seconds left
h=$((m/60)) hm=$((m%60)) # hours and minutes left
# Re-synchronise
now=$(date +%s) sleft=$((target - now)) # recalculate time left, multiple 60s sleeps and date calls have some overhead.
correction=$((sleft-left))
if (( ${correction#-} > 59 )); then
echo "System time change detected..."
(( sleft <= 0 )) && return # terminating as the desired time passed already
til "$1" && return # resuming the timer anew with the new time
fi
# plural calculations
(( sec > 1 )) && ss=s
(( hm != 1 )) && ms=s
(( h > 1 )) && hs=s
(( h > 0 )) && printf %s "$h hour$hs and "
(( h > 0 || hm > 0 )) && printf '%2d %s' "$hm" "minute$ms"
if [[ $showSeconds ]]; then
showSeconds=
(( h > 0 || hm > 0 )) && (( sec > 0 )) && printf %s " and "
(( sec > 0 )) && printf %s "$sec second$ss"
echo " left..."
(( sec > 0 )) && sleep "$sec" && left=$((left-sec)) && continue
else
echo " left..."
fi
fi
left=$((left-60))
sleep "$((60+correction))"
correction=0
done
}
Solution 6 - Bash
You can stop a process from executing, by sending it a SIGSTOP signal, and then get it to resume executing by sending it a SIGCONT signal.
So you could stop your script by sending is a SIGSTOP:
kill -SIGSTOP <pid>
And then use the at deamon to wake it up by sending it a SIGCONT in the same way.
Presumably, your script will inform at of when it wanted to be woken up before putting itself to sleep.
Solution 7 - Bash
I wanted an script that only checked the hours and minutes so I could run the script with the same parameters every day. I don't want to worry about which day will be tomorrow. So I used a different approach.
target="$1.$2"
cur=$(date '+%H.%M')
while test $target != $cur; do
sleep 59
cur=$(date '+%H.%M')
done
the parameters to the script are the hours and minutes, so I can write something like:
til 7 45 && mplayer song.ogg
(til is the name of the script)
no more days late at work cause you mistyped the day. cheers!
Solution 8 - Bash
To follow on SpoonMeiser's answer, here's a specific example:
$cat ./reviveself
#!/bin/bash
# save my process ID
rspid=$$
# schedule my own resuscitation
# /bin/sh seems to dislike the SIGCONT form, so I use CONT
# at can accept specific dates and times as well as relative ones
# you can even do something like "at thursday" which would occur on a
# multiple of 24 hours rather than the beginning of the day
echo "kill -CONT $rspid"|at now + 2 minutes
# knock myself unconscious
# bash is happy with symbolic signals
kill -SIGSTOP $rspid
# do something to prove I'm alive
date>>reviveself.out
$
Solution 9 - Bash
> timeToWait = $(( $end - $start ))
Beware that "timeToWait" could be a negative number! (for example, if you specify to sleep until "15:57" and now it's "15:58"). So you have to check it to avoid strange message errors:
#!/bin/bash
set -o nounset
### // Sleep until some date/time.
# // Example: sleepuntil 15:57; kdialog --msgbox "Backup needs to be done."
error() {
echo "$@" >&2
exit 1;
}
NAME_PROGRAM=$(basename "$0")
if [[ $# != 1 ]]; then
error "ERROR: program \"$NAME_PROGRAM\" needs 1 parameter and it has received: $#."
fi
current=$(date +%s.%N)
target=$(date -d "$1" +%s.%N)
seconds=$(echo "scale=9; $target - $current" | bc)
signchar=${seconds:0:1}
if [ "$signchar" = "-" ]; then
error "You need to specify in a different way the moment in which this program has to finish, probably indicating the day and the hour like in this example: $NAME_PROGRAM \"2009/12/30 10:57\"."
fi
sleep "$seconds"
# // End of file
Solution 10 - Bash
I actually wrote https://tamentis.com/projects/sleepuntil/ for this exact purpose. It's a bit over-kill most of the code comes from BSD 'at' so it's fairly standard-compliant:
$ sleepuntil noon && sendmail something
Solution 11 - Bash
You can calculate the number of seconds between now and the wake-up time and use the existing 'sleep' command.
Solution 12 - Bash
You could perhaps use 'at' to send a signal to your script, which sat waiting for that signal.
Solution 13 - Bash
Here's something I wrote just now to synchronise multiple test clients:
#!/usr/bin/python
import time
import sys
now = time.time()
mod = float(sys.argv[1])
until = now - now % mod + mod
print "sleeping until", until
while True:
delta = until - time.time()
if delta <= 0:
print "done sleeping ", time.time()
break
time.sleep(delta / 2)
This script sleeps until next "rounded" or "sharp" time.
A simple use case is to run ./sleep.py 10; ./test_client1.py in one terminal and ./sleep.py 10; ./test_client2.py in another.
Solution 14 - Bash
function sleepuntil() {
local target_time="$1"
today=$(date +"%m/%d/%Y")
current_epoch=$(date +%s)
target_epoch=$(date -d "$today $target_time" +%s)
sleep_seconds=$(( $target_epoch - $current_epoch ))
sleep $sleep_seconds
}
target_time="11:59"; sleepuntil $target_time
Solution 15 - Bash
I put together a small utility called Hypnos to do this. It's configured using the crontab syntax and blocks until that time.
#!/bin/bash
while [ 1 ]; do
hypnos "0 * * * *"
echo "running some tasks..."
# ...
done
Solution 16 - Bash
To extend the main answer, here is some valid examples regarding the date string manipulation:
sleep $(($(date -f - +%s- <<< $'+3 seconds\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'3 seconds\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'3 second\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'+2 minute\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'tomorrow\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'tomorrow 21:30\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'3 weeks\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'3 week\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'next Friday 09:00\nnow')0)) && ls
sleep $(($(date -f - +%s- <<< $'2027-01-01 00:00:01 UTC +5 hours\nnow')0)) && ls
Solution 17 - Bash
Consider also this concise Bash one-liner:
sleep $((`date -d "22:00" +%s`-`date +%s`))
This is a Bash v4.4.20(1) arithmetic expression, consisting of two date command substitutions. The first date command outputs your target until time in seconds (since 1970) and the latter the respective current time. These two numbers are separated by a minus sign for the arithmetic. As a result, you get seconds as a parameter for the sleep command.
Solution 18 - Bash
On OpenBSD, the following could be used to compact a */5 5-minute crontab(5) job into an 00 hourly one (to make sure fewer emails are generated, all whilst performing the same task at exact intervals):
#!/bin/sh -x
for k in $(jot 12 00 55)
do
echo $(date) doing stuff
sleep $(expr $(date -j +%s $(printf %02d $(expr $k + 5))) - $(date -j +%s))
done
Note that the date(1) would also break the sleep(1) by design on the final iteration, as 60 minutes is not a valid time (unless it is!), thus we won't have to wait any extra time prior to getting our email report.
Also note that should one of the iterations take more than 5 minutes allotted to it, the sleep would likewise graciously fail by design by not sleeping at all (due to what is a negative number interpreted as a command-line option, instead of wrapping around to the next hour or even eternity), thus making sure your job could still complete within the hour allotted (e.g., if only one of the iterations takes a little bit more than 5 minutes, then we would still have the time to catch up, without anything wrapping around to the next hour).
The printf(1) is needed because date expects exactly two digits for the minute specification.
Solution 19 - Bash
Use tarry. It's a tool I wrote to specifically do this.
https://github.com/metaphyze/tarry/
This is a simple command line tool for waiting until a specific time. This is not the same as "sleep" which will wait for a duration of time. This is useful if you want to execute something at a specific time or more likely execute several things at exactly the same time such as testing if a server can handle multiple very simultaneous requests. You could use it like this with "&&" on Linux, Mac, or Windows:
tarry -until=16:03:04 && someOtherCommand
This would wait until 4:03:04 PM and then execute someOtherCommand. Here's a Linux/Mac example of how to run multiple requests all scheduled to start at the same time:
for request in 1 2 3 4 5 6 7 8 9 10
do
tarry -until=16:03:04 && date > results.$request &
done
Ubuntu, Linux, and Windows binaries are available through links on the page.