Wait until specified time has been reached. Time format is exactly the same as the format accepted by "date -d time". (bash shell) (see example in comment) Usage: $ . wait_until.sh time

wait_until.sh

##set -- "$(( `date -d "$1" +%s`-`date +%s` ))"
#set -- "$(( `date -d "$1" +%s`-`date +%s` ))" "$2"
#[[ "$2" == "" ]] || set -- "$(( $1+$2*60 ))"
##echo "$1"
#set -- "$(( $1>=0 ? $1 : 0 ))"
#. /dev/null
##echo "$1"
#sleep -- "$1"
# * the above not work after suspend or hibernate

#set -- "$(( `date -d "$1" +%s`-`date +%s` ))" "$2"
#set -- "`date -d "$1" +%s`" "$2"
# * when system running into low resource, execution of date will error like unable to fork, so retry until success
set -- "`until date -d "$1" +%s ; do sleep 5 ; done`" "$2"
#[[ "$2" == "" ]] || set -- "$(( $1+$2*60 ))"
#set -- "$(( $1>=0 ? $1 : 0 ))"
# * need this to make "$@" be local to this script when use the script via sourcing like ". wait_until.sh ...",
#   this will avoid "$@" of the caller being overwritten
# ** sourcing consume less resources and less overhead than executing the script
. /dev/null
#sleep -- "$1"
# * '10:00' --> '09:59:55'
#while (( "$1"-5 > "`date +%s`" )) ; do sleep 5 ; done
##while (( "$1" > "`date +%s`" )) ; do sleep 5 ; done
#while (( "$1" > "`date +%s`" )) ; do sleep 1 ; done
# * use "until" instead of "while" to retry execute date when low resource
# ** as both (( "" >= "0" )) and (( "" < "0" )) is false
until (( "`date +%s`" >= "$1"-5 )) ; do sleep 5 ; done
#until (( "`date +%s`" >= "$1" )) ; do sleep 5 ; done
until (( "`date +%s`" >= "$1" )) ; do sleep 1 ; done

More description in th_TH language,
https://m.facebook.com/story.php?story_fbid=10156426462221192&id=705691191&refid=17&__tn__=*s-R

Example: $ { . wait_until.sh '+1day 16:00' ; wget http://... ; xmessage done wget ; } &

It is designed to support continued operation after resuming from hibernate.
To ensure correct behavior after hibernation, the script needs to poll every 5 seconds, and during the last 5 seconds, it will poll every 1 second.
Although it doesn't ensure 100% correct behavior, the maximum error is no more than +5 seconds.