#1 2021-03-26 19:09:46

Colonel Panic

Member

Registered: 2018-11-13

Posts: 1,429

Countdown timer in a terminal

Hi everybody,

I know that some people here write or use bash scripts, and there's recently been a thread about alarm clock scripts.

https://forums.bunsenlabs.org/viewtopic.php?id=6257

Here's something similar; I've been looking for a way to have a simple, unobtrusive countdown timer, and came across this script (which works in a terminal and counts down 20 seconds at a time);

seconds=20; date1=$((`date +%s` + $seconds));
while [ "$date1" -ge `date +%s` ]; do
  echo -ne "$(date -u --date @$(($date1 - `date +%s` )) +%H:%M:%S)\r";
done

I'm using it now and can testify that it works.

Here's a thread with some more and similar ideas in it;

https://superuser.com/questions/611538/ … a-terminal

Last edited by Colonel Panic (2021-03-26 19:11:15)

Obadobo

Member

Registered: 2015-10-26

Posts: 14

Re: Countdown timer in a terminal

Thanks

ohnonot

...again

Registered: 2015-09-29

Posts: 5,592

Re: Countdown timer in a terminal

... bash ... works in a terminal and counts down 20 seconds at a time ...

seconds=20; date1=$((`date +%s` + $seconds));
while [ "$date1" -ge `date +%s` ]; do
  echo -ne "$(date -u --date @$(($date1 - `date +%s` )) +%H:%M:%S)\r";
done

This is actually pretty resource intensive; adding a "sleep 0.1" already reduces the strain significantly.
But why call date twice in a loop over and over when all you want is to count down seconds...

seconds=20
end_seconds=$((SECONDS+seconds))
while ((SECONDS<end_seconds)); do
    printf ' %2d\r' "$((end_seconds-SECONDS))"
    sleep 0.1
done

see 'man bash' => Shell variables => SECONDS.

brontosaurusrex

Middle Office

Registered: 2015-09-29

Posts: 2,746

Re: Countdown timer in a terminal

1. An zsh oneliner attempt

c=20; repeat c {(( c-- )); sleep 1; echo $c}

2. Similar, but countdown in single line

c=20; d="$c"; echo -ne "$c\r"; repeat c {(( c-- )); sleep 1; echo -ne "${(l(2)(0))c}\r"} && echo "$d seconds has passe
d."

3. A fun one that draws a little reverse staircase using perc2 script

c=20; set +m; perc=$(( 100.0/c )); perc2 100 & repeat c {(( c-- )); sleep 1 & var="$(perc2 $(( perc * c )))" ; wait; echo "$var" }

Note: set +m disables shell monitoring, so that it will not report subshell returns.

███████████████████████████████████████████████████████████████████████████▎
█████████████████████████████████████████████████████████████████▊
████████████████████████████████████████████████████████▍
███████████████████████████████████████████████
█████████████████████████████████████▋
████████████████████████████▎
██████████████████▊
█████████▍

p.s. Both examples will not achieve millisecond precision. To test:

time ( c=20; set +m; perc=$(( 100.0/c )); perc2 100 & repeat c {(( c-- )); sleep 1 & var="$(perc2 $(( perc * c )))" ; wait; echo "$var" } )
# returns: 20.156 total on this machine.

Last edited by brontosaurusrex (2021-04-11 09:05:09)

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ohnonot

...again

Registered: 2015-09-29

Posts: 5,592

Re: Countdown timer in a terminal

p.s. Both examples will not achieve millisecond precision.

Because you rely on the sleep command to measure time; the other examples above actually measure the time (one with `date`, the other with the bash builtin SECONDS) while counting down.

brontosaurusrex

Middle Office

Registered: 2015-09-29

Posts: 2,746

Re: Countdown timer in a terminal

Your version takes 19 seconds, so I guess It's superluminal?
edit: The ops version takes 20.238s
I win. 
Prettyfied script version (zsh) of my 2nd example. And a progress-bar version (also zsh).

Last edited by brontosaurusrex (2021-04-11 13:08:51)

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My website full of interesting stuff.

ohnonot

...again

Registered: 2015-09-29

Posts: 5,592

Re: Countdown timer in a terminal

Your version takes 19 seconds, so I guess It's superluminal?
edit: The ops version takes 20.238s
I win. 
Prettyfied script version (zsh) of my 2nd example. And a progress-bar version (also zsh).

My version takes 19s because it stops 1s early.

But the logic of my argument stands: since you never know how long actual script execution takes, you cannot rely solely on the sleep delays to measure time. It will get less precise the longer it runs.
(My version also uses sleep, but only to keep it from taking 100% CPU, not to measure time.)

But whatever, just continue faffing around with your version. It sure is prettier.

Last edited by ohnonot (2021-04-12 04:45:24)

brontosaurusrex

Middle Office

Registered: 2015-09-29

Posts: 2,746

Re: Countdown timer in a terminal

Uhmm, ok, still you two are doing low-level stuff in bash script, my 1st script reports 0% cpu usage for example. I'am fine with tie, little reluctant, but ok

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brontosaurusrex

Middle Office

Registered: 2015-09-29

Posts: 2,746

Re: Countdown timer in a terminal

Doing some 'research', this one is neat (and correct and low cpu)
https://github.com/trehn/termdown (pip install termdown)

Similar in go (super correct)
https://github.com/antonmedv/countdown

time countdown 25s -up
countdown 25s -up  0.02s user 0.00s system 0% cpu 25.011 total

Last edited by brontosaurusrex (2021-04-13 09:23:28)

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My website full of interesting stuff.

Colonel Panic

Member

Registered: 2018-11-13

Posts: 1,429

Re: Countdown timer in a terminal

Good to see this thread's still going although I don't have the knowledge to contribute further. I haven't read all the posts yet but I like the two (termdown and countdown) brontosaurusrex has just mentioned.

Last edited by Colonel Panic (2021-04-17 23:53:24)