Shell: is it possible to delay a command without using `sleep`?

up vote
13
down vote

favorite

Are there any substitutes, alternatives or bash tricks for delaying commands without using sleep? For example, performing the below command without actually using sleep:

$ sleep 10 && echo "This is a test"

edited 23 hours ago

Fabby

2,94411125

asked yesterday

user321697

764

New contributor

28

What's wrong with sleep?
– muru
yesterday

2

There's no real reason other than curiosity. I thought it would be interesting to learn some alternative solutions. I think at might be one, but I couldn't find any usage examples.
– user321697
yesterday

What do you want to wait for? If there’s an event you’re waiting for, you’d typically use a while loop, testing for the condition and sleeping for one second (or whatever makes sense). If you’re waiting for a child process to finish, then you can use the wait builtin. If it’s something else, do elaborate, please.
– Grega Bremec
23 hours ago

@user321697 “at” is to schedule single jobs. they are executed by the atd service, so they won’t pause your shell script. one use case for at would be to have it do something at a specified time (async) and create a marker file when it’s finished, while your script is waiting for that file to appear in a while loop. you could achieve a similar effect by scheduling a job to send your script a SIGCONT and then freezing your script by sending yourself a SIGSTOP.
– Grega Bremec
23 hours ago

1

I came here expecting everyone to suggest a spinlock. I'm pleasantly surprised by all the answers.
– Daan van Hoek
19 hours ago

|
show 3 more comments

up vote
13
down vote

favorite

Are there any substitutes, alternatives or bash tricks for delaying commands without using sleep? For example, performing the below command without actually using sleep:

$ sleep 10 && echo "This is a test"

edited 23 hours ago

Fabby

2,94411125

asked yesterday

user321697

764

New contributor

28

What's wrong with sleep?
– muru
yesterday

2

There's no real reason other than curiosity. I thought it would be interesting to learn some alternative solutions. I think at might be one, but I couldn't find any usage examples.
– user321697
yesterday

What do you want to wait for? If there’s an event you’re waiting for, you’d typically use a while loop, testing for the condition and sleeping for one second (or whatever makes sense). If you’re waiting for a child process to finish, then you can use the wait builtin. If it’s something else, do elaborate, please.
– Grega Bremec
23 hours ago

@user321697 “at” is to schedule single jobs. they are executed by the atd service, so they won’t pause your shell script. one use case for at would be to have it do something at a specified time (async) and create a marker file when it’s finished, while your script is waiting for that file to appear in a while loop. you could achieve a similar effect by scheduling a job to send your script a SIGCONT and then freezing your script by sending yourself a SIGSTOP.
– Grega Bremec
23 hours ago

1

I came here expecting everyone to suggest a spinlock. I'm pleasantly surprised by all the answers.
– Daan van Hoek
19 hours ago

|
show 3 more comments

up vote
13
down vote

favorite

Are there any substitutes, alternatives or bash tricks for delaying commands without using sleep? For example, performing the below command without actually using sleep:

$ sleep 10 && echo "This is a test"

edited 23 hours ago

Fabby

2,94411125

asked yesterday

user321697

764

New contributor

Are there any substitutes, alternatives or bash tricks for delaying commands without using sleep? For example, performing the below command without actually using sleep:

$ sleep 10 && echo "This is a test"

linux bash shell-script shell sleep

edited 23 hours ago

Fabby

2,94411125

asked yesterday

user321697

764

New contributor

edited 23 hours ago

Fabby

2,94411125

asked yesterday

user321697

764

New contributor

edited 23 hours ago

Fabby

2,94411125

edited 23 hours ago

Fabby

2,94411125

edited 23 hours ago

Fabby

2,94411125

asked yesterday

user321697

764

New contributor

asked yesterday

user321697

764

asked yesterday

user321697

764

New contributor

user321697 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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28

What's wrong with sleep?
– muru
yesterday

2

There's no real reason other than curiosity. I thought it would be interesting to learn some alternative solutions. I think at might be one, but I couldn't find any usage examples.
– user321697
yesterday

What do you want to wait for? If there’s an event you’re waiting for, you’d typically use a while loop, testing for the condition and sleeping for one second (or whatever makes sense). If you’re waiting for a child process to finish, then you can use the wait builtin. If it’s something else, do elaborate, please.
– Grega Bremec
23 hours ago

@user321697 “at” is to schedule single jobs. they are executed by the atd service, so they won’t pause your shell script. one use case for at would be to have it do something at a specified time (async) and create a marker file when it’s finished, while your script is waiting for that file to appear in a while loop. you could achieve a similar effect by scheduling a job to send your script a SIGCONT and then freezing your script by sending yourself a SIGSTOP.
– Grega Bremec
23 hours ago

1

I came here expecting everyone to suggest a spinlock. I'm pleasantly surprised by all the answers.
– Daan van Hoek
19 hours ago

|
show 3 more comments

28

What's wrong with sleep?
– muru
yesterday

2

There's no real reason other than curiosity. I thought it would be interesting to learn some alternative solutions. I think at might be one, but I couldn't find any usage examples.
– user321697
yesterday

What do you want to wait for? If there’s an event you’re waiting for, you’d typically use a while loop, testing for the condition and sleeping for one second (or whatever makes sense). If you’re waiting for a child process to finish, then you can use the wait builtin. If it’s something else, do elaborate, please.
– Grega Bremec
23 hours ago

@user321697 “at” is to schedule single jobs. they are executed by the atd service, so they won’t pause your shell script. one use case for at would be to have it do something at a specified time (async) and create a marker file when it’s finished, while your script is waiting for that file to appear in a while loop. you could achieve a similar effect by scheduling a job to send your script a SIGCONT and then freezing your script by sending yourself a SIGSTOP.
– Grega Bremec
23 hours ago

1

I came here expecting everyone to suggest a spinlock. I'm pleasantly surprised by all the answers.
– Daan van Hoek
19 hours ago

What's wrong with sleep?
– muru
yesterday

There's no real reason other than curiosity. I thought it would be interesting to learn some alternative solutions. I think at might be one, but I couldn't find any usage examples.
– user321697
yesterday

What do you want to wait for? If there’s an event you’re waiting for, you’d typically use a while loop, testing for the condition and sleeping for one second (or whatever makes sense). If you’re waiting for a child process to finish, then you can use the wait builtin. If it’s something else, do elaborate, please.
– Grega Bremec
23 hours ago

@user321697 “at” is to schedule single jobs. they are executed by the atd service, so they won’t pause your shell script. one use case for at would be to have it do something at a specified time (async) and create a marker file when it’s finished, while your script is waiting for that file to appear in a while loop. you could achieve a similar effect by scheduling a job to send your script a SIGCONT and then freezing your script by sending yourself a SIGSTOP.
– Grega Bremec
23 hours ago

I came here expecting everyone to suggest a spinlock. I'm pleasantly surprised by all the answers.
– Daan van Hoek
19 hours ago

|
show 3 more comments

9 Answers
9

active

oldest

votes

up vote
8
down vote

accepted

You have alternatives to sleep: They are at and cron. Contrary to sleep these need you to provide the time at which you need them to run.

Make sure the atd service is running by executing service atd status.

Now let's say the date is 11:17 am UTC; if you need to execute a command at 11:25 UTC, the syntax is: echo "This is a test" | at 11:25.

Now keep in mind that atd by default will not be logging the completion of the jobs. For more refer this link. It's better that your application has its own logging.

You can schedule jobs in cron, for more refer : man cron to see its options or crontab -e to add new jobs. /var/log/cron can be checked for the info on execution on jobs.

FYI sleep system call suspends the current execution and schedules it w.r.t. the argument passed to it.

EDIT:

As @Gaius mentioned , you can also add minutes time to at command.But lets say time is 12:30:30 and now you ran the scheduler with now +1 minutes. Even though 1 minute, which translates to 60 seconds was specified , the at doesn't really wait till 12:31:30 to execute the job, rather it executes the job at 12:31:00. The time-units can be minutes, hours, days, or weeks. For more refer man at

e.g: echo "ls" | at now +1 minutes

edited 17 hours ago

answered 23 hours ago

sai sasanka

64919

4

This is not true, you can schedule an at job for say now +1 minute, to run in a minutes time
– Gaius
18 hours ago

add a comment |

up vote
16
down vote

With bash builtins, you can do:

coproc read -t 10 && wait "$!" || true

To sleep for 10 seconds without using sleep. The coproc is to make so that read's stdin is a pipe where nothing will ever come out from. || true is because wait's exit status will reflect a SIGALRM delivery which would cause the shell to exit if the errexit option is set.

In other shells:

mksh and ksh93 have sleep built-in, no point in using anything else there (though they both also support read -t).

zsh also supports read -t, but also has a builtin wrapper around select(), so you can also use:

zmodload zsh/zselect

zselect -t 1000 # centiseconds

If what you want is schedule things to be run from an interactive shell session, see also the zsh/sched module in zsh.

edited 22 hours ago

answered 23 hours ago

Stéphane Chazelas

294k54551893

Would you consider read -t 10 < /dev/zero || true ?
– Jeff Schaller
20 hours ago

5

@JeffSchaller I would avoid it as that's a busy loop.
– Stéphane Chazelas
20 hours ago

@StéphaneChazelas I wouldn't expect that to be a busy loop – I'd expect any shell's read to be implemented using select(2) or something similar (implying that read-with-timeout would be a good answer to this question). I'm expressing surprise rather than contradicting you, but can you point to further discussion of this?
– Norman Gray
19 hours ago

2

@NormanGray, /dev/zero is a file that contains an infinite amount of data (NUL bytes). So read will read as much as it can during those 10 seconds. Thankfully, in the case of bash which doesn't support storing NUL bytes in its variables, that won't use up any memory, but that will still hog CPU resources.
– Stéphane Chazelas
19 hours ago

1

@NormanGray, if run from a terminal, /dev/stdout would be the tty device, so it would have side effects (like stopping the script if run in background) and would return if the user presses enter for instance. read -t 10 /dev/stdout | : would work on Linux, but on Linux only, while coproc should work regardless of the OS.
– Stéphane Chazelas
19 hours ago

|
show 1 more comment

up vote
5
down vote

Using the bash built-in variable $SECONDS and a busy-loop:

for((target=$((SECONDS + 10)); SECONDS < target; true)); do :; done

answered 21 hours ago

Jeff Schaller

36.1k952119

2

That would in effect pause for a duration ranging somewhere in between 9 and 10 seconds though (due to a bug in bash; zsh and mksh had similar issues but have been fixed since)
– Stéphane Chazelas
21 hours ago

4

A good way to make heat.
– ctrl-alt-delor
20 hours ago

4

won't be the first time I'm accused of being full of hot air! :)
– Jeff Schaller
20 hours ago

add a comment |

up vote
5
down vote

Since there are answers which are suggesting to use the non-standard -t delay option of read, here is a way to do a timed-out read in a standard shell:

{ ss=`stty -g`; stty -icanon min 0 time 20; read foo; stty "$ss"; }

The argument to stty time is in tenths of second.

answered 17 hours ago

mosvy

4,323221

add a comment |

up vote
3
down vote

There is no built-in, that does the same as sleep (unless sleep is built-in). However there are some other commands that will wait.

A few include.

at and cron: used to schedule tasks at a specific time.

inotifywait: used to wait for a file, or files to be modified/removed/added/etc

edited 23 hours ago

Fabby

2,94411125

answered 23 hours ago

ctrl-alt-delor

9,96331954

Thanks for this. Could you provide an example for performing a scheduled task (10 seconds from now) with at?
– user321697
23 hours ago

1

an edit and an upvote! ;-)
– Fabby
23 hours ago

cron store tasks in crontab, right? Where does at store the scheduled data?
– user321697
23 hours ago

@user321697 Already answered here
– Fabby
23 hours ago

Sorry for reverting back your edit to the Q: you changed the OPs question's main purpose which would invalidate the simplest answer of all... ¯_(ツ)_/¯
– Fabby
23 hours ago

|
show 1 more comment

up vote
2
down vote

the oldest trick in the book:

read && echo "This is a test"

Just hit Enter and it'll continue!

answered 23 hours ago

Fabby

2,94411125

This wont if the process needs to be run interaction free or in the background right?
– sai sasanka
23 hours ago

@saisasanka Deleted my superfluous comments please ping me in chat after you've done the same, so I can remove this last one... ;-)
– Fabby
22 hours ago

add a comment |

up vote
2
down vote

Back in the days of microcomputers running BASIC, delays were usually accomplished with an empty loop:

FOR I = 1 TO 10000:NEXT

The same principle could be used to insert a delay in a shell script:

COUNTER=0; while [ $COUNTER -lt 10000 ]; do :; let COUNTER=COUNTER+1; done

Of course, the problem with this approach is that the length of the delay will vary from machine to machine according to its processor speed (or even on the same machine under different loads). Unlike sleep, it will probably also max out your CPU (or one of its cores).

answered 22 hours ago

Psychonaut

314212

2

A good way to make heat.
– ctrl-alt-delor
20 hours ago

Delay-loops are a terrible idea for anything except the very shortest of sleeps (a couple nanoseconds or clock cycles in a device driver) on any modern CPU that can run a Unix-like OS. i.e. a sleep so short you can't usefully have the CPU do anything else while waiting, like schedule another process or enter a low-power sleep state before waking on a timer interrupt. Dynamic CPU-frequency makes it impossible to even calibrate a delay loop for counts per second, except as a minimum delay potentially sleeping a lot longer at low clock speeds before ramping up.
– Peter Cordes
12 hours ago

Ancient computers had a power consumption that was much less dependent on workload. Modern CPUs need to dynamically power down different parts of the chip as much as possible to not melt (e.g. power down parts of the FPU or SIMD execution units while only integer code is running, or at least gate the clock signal to parts of the chip that don't need to be switching). And entering a low-power sleep state when idle (instead of spinning in an infinite loop waiting for timer interrupts) is also more recent than the ancient computers you mention.
– Peter Cordes
12 hours ago

For more about CPU history, see Modern Microprocessors A 90-Minute Guide! - lighterra.com/papers/modernmicroprocessors.
– Peter Cordes
12 hours ago

add a comment |

up vote
1
down vote

Some other ideas.

top -d10 -n2 >/dev/null



vmstat 10 2 >/dev/null



sar 10 1 >/dev/null



timeout 10s tail -f /dev/null

answered 12 hours ago

steve

13.6k22452

add a comment |

up vote
0
down vote

A classic from the Land of Windows and Batches:

ping -c 11 localhost >/dev/null && echo "This is a test"

answered 2 hours ago

Joker_vD

101

New contributor

add a comment |

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9 Answers
9

active

oldest

votes

9 Answers
9

active

oldest

votes

up vote
8
down vote

accepted

You have alternatives to sleep: They are at and cron. Contrary to sleep these need you to provide the time at which you need them to run.

Make sure the atd service is running by executing service atd status.

Now let's say the date is 11:17 am UTC; if you need to execute a command at 11:25 UTC, the syntax is: echo "This is a test" | at 11:25.

Now keep in mind that atd by default will not be logging the completion of the jobs. For more refer this link. It's better that your application has its own logging.

You can schedule jobs in cron, for more refer : man cron to see its options or crontab -e to add new jobs. /var/log/cron can be checked for the info on execution on jobs.

FYI sleep system call suspends the current execution and schedules it w.r.t. the argument passed to it.

EDIT:

e.g: echo "ls" | at now +1 minutes

edited 17 hours ago

answered 23 hours ago

sai sasanka

64919

4

This is not true, you can schedule an at job for say now +1 minute, to run in a minutes time
– Gaius
18 hours ago

add a comment |

up vote
8
down vote

accepted

You have alternatives to sleep: They are at and cron. Contrary to sleep these need you to provide the time at which you need them to run.

Make sure the atd service is running by executing service atd status.

Now let's say the date is 11:17 am UTC; if you need to execute a command at 11:25 UTC, the syntax is: echo "This is a test" | at 11:25.

Now keep in mind that atd by default will not be logging the completion of the jobs. For more refer this link. It's better that your application has its own logging.

You can schedule jobs in cron, for more refer : man cron to see its options or crontab -e to add new jobs. /var/log/cron can be checked for the info on execution on jobs.

FYI sleep system call suspends the current execution and schedules it w.r.t. the argument passed to it.

EDIT:

e.g: echo "ls" | at now +1 minutes

edited 17 hours ago

answered 23 hours ago

sai sasanka

64919

4

This is not true, you can schedule an at job for say now +1 minute, to run in a minutes time
– Gaius
18 hours ago

add a comment |

up vote
8
down vote

accepted

You have alternatives to sleep: They are at and cron. Contrary to sleep these need you to provide the time at which you need them to run.

Make sure the atd service is running by executing service atd status.

Now let's say the date is 11:17 am UTC; if you need to execute a command at 11:25 UTC, the syntax is: echo "This is a test" | at 11:25.

Now keep in mind that atd by default will not be logging the completion of the jobs. For more refer this link. It's better that your application has its own logging.

You can schedule jobs in cron, for more refer : man cron to see its options or crontab -e to add new jobs. /var/log/cron can be checked for the info on execution on jobs.

FYI sleep system call suspends the current execution and schedules it w.r.t. the argument passed to it.

EDIT:

e.g: echo "ls" | at now +1 minutes

edited 17 hours ago

answered 23 hours ago

sai sasanka

64919

You have alternatives to sleep: They are at and cron. Contrary to sleep these need you to provide the time at which you need them to run.

Make sure the atd service is running by executing service atd status.

Now let's say the date is 11:17 am UTC; if you need to execute a command at 11:25 UTC, the syntax is: echo "This is a test" | at 11:25.

Now keep in mind that atd by default will not be logging the completion of the jobs. For more refer this link. It's better that your application has its own logging.

You can schedule jobs in cron, for more refer : man cron to see its options or crontab -e to add new jobs. /var/log/cron can be checked for the info on execution on jobs.

FYI sleep system call suspends the current execution and schedules it w.r.t. the argument passed to it.

EDIT:

e.g: echo "ls" | at now +1 minutes

edited 17 hours ago

answered 23 hours ago

sai sasanka

64919

edited 17 hours ago

answered 23 hours ago

sai sasanka

64919

answered 23 hours ago

sai sasanka

64919

answered 23 hours ago

sai sasanka

64919

4

This is not true, you can schedule an at job for say now +1 minute, to run in a minutes time
– Gaius
18 hours ago

add a comment |

4

This is not true, you can schedule an at job for say now +1 minute, to run in a minutes time
– Gaius
18 hours ago

This is not true, you can schedule an at job for say now +1 minute, to run in a minutes time
– Gaius
18 hours ago

add a comment |

up vote
16
down vote

With bash builtins, you can do:

coproc read -t 10 && wait "$!" || true

In other shells:

mksh and ksh93 have sleep built-in, no point in using anything else there (though they both also support read -t).

zsh also supports read -t, but also has a builtin wrapper around select(), so you can also use:

zmodload zsh/zselect

zselect -t 1000 # centiseconds

If what you want is schedule things to be run from an interactive shell session, see also the zsh/sched module in zsh.

edited 22 hours ago

answered 23 hours ago

Stéphane Chazelas

294k54551893

Would you consider read -t 10 < /dev/zero || true ?
– Jeff Schaller
20 hours ago

5

@JeffSchaller I would avoid it as that's a busy loop.
– Stéphane Chazelas
20 hours ago

@StéphaneChazelas I wouldn't expect that to be a busy loop – I'd expect any shell's read to be implemented using select(2) or something similar (implying that read-with-timeout would be a good answer to this question). I'm expressing surprise rather than contradicting you, but can you point to further discussion of this?
– Norman Gray
19 hours ago

2

@NormanGray, /dev/zero is a file that contains an infinite amount of data (NUL bytes). So read will read as much as it can during those 10 seconds. Thankfully, in the case of bash which doesn't support storing NUL bytes in its variables, that won't use up any memory, but that will still hog CPU resources.
– Stéphane Chazelas
19 hours ago

1

@NormanGray, if run from a terminal, /dev/stdout would be the tty device, so it would have side effects (like stopping the script if run in background) and would return if the user presses enter for instance. read -t 10 /dev/stdout | : would work on Linux, but on Linux only, while coproc should work regardless of the OS.
– Stéphane Chazelas
19 hours ago

|
show 1 more comment

up vote
16
down vote

With bash builtins, you can do:

coproc read -t 10 && wait "$!" || true

In other shells:

mksh and ksh93 have sleep built-in, no point in using anything else there (though they both also support read -t).

zsh also supports read -t, but also has a builtin wrapper around select(), so you can also use:

zmodload zsh/zselect

zselect -t 1000 # centiseconds

If what you want is schedule things to be run from an interactive shell session, see also the zsh/sched module in zsh.

edited 22 hours ago

answered 23 hours ago

Stéphane Chazelas

294k54551893

Would you consider read -t 10 < /dev/zero || true ?
– Jeff Schaller
20 hours ago

5

@JeffSchaller I would avoid it as that's a busy loop.
– Stéphane Chazelas
20 hours ago

@StéphaneChazelas I wouldn't expect that to be a busy loop – I'd expect any shell's read to be implemented using select(2) or something similar (implying that read-with-timeout would be a good answer to this question). I'm expressing surprise rather than contradicting you, but can you point to further discussion of this?
– Norman Gray
19 hours ago

2

@NormanGray, /dev/zero is a file that contains an infinite amount of data (NUL bytes). So read will read as much as it can during those 10 seconds. Thankfully, in the case of bash which doesn't support storing NUL bytes in its variables, that won't use up any memory, but that will still hog CPU resources.
– Stéphane Chazelas
19 hours ago

1

@NormanGray, if run from a terminal, /dev/stdout would be the tty device, so it would have side effects (like stopping the script if run in background) and would return if the user presses enter for instance. read -t 10 /dev/stdout | : would work on Linux, but on Linux only, while coproc should work regardless of the OS.
– Stéphane Chazelas
19 hours ago

|
show 1 more comment

up vote
16
down vote

With bash builtins, you can do:

coproc read -t 10 && wait "$!" || true

In other shells:

mksh and ksh93 have sleep built-in, no point in using anything else there (though they both also support read -t).

zsh also supports read -t, but also has a builtin wrapper around select(), so you can also use:

zmodload zsh/zselect

zselect -t 1000 # centiseconds

If what you want is schedule things to be run from an interactive shell session, see also the zsh/sched module in zsh.

edited 22 hours ago

answered 23 hours ago

Stéphane Chazelas

294k54551893

With bash builtins, you can do:

coproc read -t 10 && wait "$!" || true

In other shells:

mksh and ksh93 have sleep built-in, no point in using anything else there (though they both also support read -t).

zsh also supports read -t, but also has a builtin wrapper around select(), so you can also use:

zmodload zsh/zselect

zselect -t 1000 # centiseconds

If what you want is schedule things to be run from an interactive shell session, see also the zsh/sched module in zsh.

edited 22 hours ago

answered 23 hours ago

Stéphane Chazelas

294k54551893

edited 22 hours ago

answered 23 hours ago

Stéphane Chazelas

294k54551893

answered 23 hours ago

Stéphane Chazelas

294k54551893

answered 23 hours ago

Stéphane Chazelas

294k54551893

Would you consider read -t 10 < /dev/zero || true ?
– Jeff Schaller
20 hours ago

5

@JeffSchaller I would avoid it as that's a busy loop.
– Stéphane Chazelas
20 hours ago

@StéphaneChazelas I wouldn't expect that to be a busy loop – I'd expect any shell's read to be implemented using select(2) or something similar (implying that read-with-timeout would be a good answer to this question). I'm expressing surprise rather than contradicting you, but can you point to further discussion of this?
– Norman Gray
19 hours ago

2

@NormanGray, /dev/zero is a file that contains an infinite amount of data (NUL bytes). So read will read as much as it can during those 10 seconds. Thankfully, in the case of bash which doesn't support storing NUL bytes in its variables, that won't use up any memory, but that will still hog CPU resources.
– Stéphane Chazelas
19 hours ago

1

@NormanGray, if run from a terminal, /dev/stdout would be the tty device, so it would have side effects (like stopping the script if run in background) and would return if the user presses enter for instance. read -t 10 /dev/stdout | : would work on Linux, but on Linux only, while coproc should work regardless of the OS.
– Stéphane Chazelas
19 hours ago

|
show 1 more comment

Would you consider read -t 10 < /dev/zero || true ?
– Jeff Schaller
20 hours ago

5

@JeffSchaller I would avoid it as that's a busy loop.
– Stéphane Chazelas
20 hours ago

@StéphaneChazelas I wouldn't expect that to be a busy loop – I'd expect any shell's read to be implemented using select(2) or something similar (implying that read-with-timeout would be a good answer to this question). I'm expressing surprise rather than contradicting you, but can you point to further discussion of this?
– Norman Gray
19 hours ago

2

@NormanGray, /dev/zero is a file that contains an infinite amount of data (NUL bytes). So read will read as much as it can during those 10 seconds. Thankfully, in the case of bash which doesn't support storing NUL bytes in its variables, that won't use up any memory, but that will still hog CPU resources.
– Stéphane Chazelas
19 hours ago

1

@NormanGray, if run from a terminal, /dev/stdout would be the tty device, so it would have side effects (like stopping the script if run in background) and would return if the user presses enter for instance. read -t 10 /dev/stdout | : would work on Linux, but on Linux only, while coproc should work regardless of the OS.
– Stéphane Chazelas
19 hours ago

Would you consider read -t 10 < /dev/zero || true ?
– Jeff Schaller
20 hours ago

@JeffSchaller I would avoid it as that's a busy loop.
– Stéphane Chazelas
20 hours ago

@StéphaneChazelas I wouldn't expect that to be a busy loop – I'd expect any shell's read to be implemented using select(2) or something similar (implying that read-with-timeout would be a good answer to this question). I'm expressing surprise rather than contradicting you, but can you point to further discussion of this?
– Norman Gray
19 hours ago

@NormanGray, /dev/zero is a file that contains an infinite amount of data (NUL bytes). So read will read as much as it can during those 10 seconds. Thankfully, in the case of bash which doesn't support storing NUL bytes in its variables, that won't use up any memory, but that will still hog CPU resources.
– Stéphane Chazelas
19 hours ago

@NormanGray, if run from a terminal, /dev/stdout would be the tty device, so it would have side effects (like stopping the script if run in background) and would return if the user presses enter for instance. read -t 10 /dev/stdout | : would work on Linux, but on Linux only, while coproc should work regardless of the OS.
– Stéphane Chazelas
19 hours ago

|
show 1 more comment

up vote
5
down vote

Using the bash built-in variable $SECONDS and a busy-loop:

for((target=$((SECONDS + 10)); SECONDS < target; true)); do :; done

answered 21 hours ago

Jeff Schaller

36.1k952119

2

That would in effect pause for a duration ranging somewhere in between 9 and 10 seconds though (due to a bug in bash; zsh and mksh had similar issues but have been fixed since)
– Stéphane Chazelas
21 hours ago

4

A good way to make heat.
– ctrl-alt-delor
20 hours ago

4

won't be the first time I'm accused of being full of hot air! :)
– Jeff Schaller
20 hours ago

add a comment |

up vote
5
down vote

Using the bash built-in variable $SECONDS and a busy-loop:

for((target=$((SECONDS + 10)); SECONDS < target; true)); do :; done

answered 21 hours ago

Jeff Schaller

36.1k952119

2

That would in effect pause for a duration ranging somewhere in between 9 and 10 seconds though (due to a bug in bash; zsh and mksh had similar issues but have been fixed since)
– Stéphane Chazelas
21 hours ago

4

A good way to make heat.
– ctrl-alt-delor
20 hours ago

4

won't be the first time I'm accused of being full of hot air! :)
– Jeff Schaller
20 hours ago

add a comment |

up vote
5
down vote

Using the bash built-in variable $SECONDS and a busy-loop:

for((target=$((SECONDS + 10)); SECONDS < target; true)); do :; done

answered 21 hours ago

Jeff Schaller

36.1k952119

Using the bash built-in variable $SECONDS and a busy-loop:

for((target=$((SECONDS + 10)); SECONDS < target; true)); do :; done

answered 21 hours ago

Jeff Schaller

36.1k952119

answered 21 hours ago

Jeff Schaller

36.1k952119

answered 21 hours ago

Jeff Schaller

36.1k952119

answered 21 hours ago

Jeff Schaller

36.1k952119

2

That would in effect pause for a duration ranging somewhere in between 9 and 10 seconds though (due to a bug in bash; zsh and mksh had similar issues but have been fixed since)
– Stéphane Chazelas
21 hours ago

4

A good way to make heat.
– ctrl-alt-delor
20 hours ago

4

won't be the first time I'm accused of being full of hot air! :)
– Jeff Schaller
20 hours ago

add a comment |

2

That would in effect pause for a duration ranging somewhere in between 9 and 10 seconds though (due to a bug in bash; zsh and mksh had similar issues but have been fixed since)
– Stéphane Chazelas
21 hours ago

4

A good way to make heat.
– ctrl-alt-delor
20 hours ago

4

won't be the first time I'm accused of being full of hot air! :)
– Jeff Schaller
20 hours ago

That would in effect pause for a duration ranging somewhere in between 9 and 10 seconds though (due to a bug in bash; zsh and mksh had similar issues but have been fixed since)
– Stéphane Chazelas
21 hours ago

A good way to make heat.
– ctrl-alt-delor
20 hours ago

won't be the first time I'm accused of being full of hot air! :)
– Jeff Schaller
20 hours ago

add a comment |

up vote
5
down vote

Since there are answers which are suggesting to use the non-standard -t delay option of read, here is a way to do a timed-out read in a standard shell:

{ ss=`stty -g`; stty -icanon min 0 time 20; read foo; stty "$ss"; }

The argument to stty time is in tenths of second.

answered 17 hours ago

mosvy

4,323221

add a comment |

up vote
5
down vote

Since there are answers which are suggesting to use the non-standard -t delay option of read, here is a way to do a timed-out read in a standard shell:

{ ss=`stty -g`; stty -icanon min 0 time 20; read foo; stty "$ss"; }

The argument to stty time is in tenths of second.

answered 17 hours ago

mosvy

4,323221

add a comment |

up vote
5
down vote

Since there are answers which are suggesting to use the non-standard -t delay option of read, here is a way to do a timed-out read in a standard shell:

{ ss=`stty -g`; stty -icanon min 0 time 20; read foo; stty "$ss"; }

The argument to stty time is in tenths of second.

answered 17 hours ago

mosvy

4,323221

Since there are answers which are suggesting to use the non-standard -t delay option of read, here is a way to do a timed-out read in a standard shell:

{ ss=`stty -g`; stty -icanon min 0 time 20; read foo; stty "$ss"; }

The argument to stty time is in tenths of second.

answered 17 hours ago

mosvy

4,323221

answered 17 hours ago

mosvy

4,323221

answered 17 hours ago

mosvy

4,323221

answered 17 hours ago

mosvy

4,323221

add a comment |

up vote
3
down vote

There is no built-in, that does the same as sleep (unless sleep is built-in). However there are some other commands that will wait.

A few include.

at and cron: used to schedule tasks at a specific time.

inotifywait: used to wait for a file, or files to be modified/removed/added/etc

edited 23 hours ago

Fabby

2,94411125

answered 23 hours ago

ctrl-alt-delor

9,96331954

Thanks for this. Could you provide an example for performing a scheduled task (10 seconds from now) with at?
– user321697
23 hours ago

1

an edit and an upvote! ;-)
– Fabby
23 hours ago

cron store tasks in crontab, right? Where does at store the scheduled data?
– user321697
23 hours ago

@user321697 Already answered here
– Fabby
23 hours ago

Sorry for reverting back your edit to the Q: you changed the OPs question's main purpose which would invalidate the simplest answer of all... ¯_(ツ)_/¯
– Fabby
23 hours ago

|
show 1 more comment

up vote
3
down vote

There is no built-in, that does the same as sleep (unless sleep is built-in). However there are some other commands that will wait.

A few include.

at and cron: used to schedule tasks at a specific time.

inotifywait: used to wait for a file, or files to be modified/removed/added/etc

edited 23 hours ago

Fabby

2,94411125

answered 23 hours ago

ctrl-alt-delor

9,96331954

Thanks for this. Could you provide an example for performing a scheduled task (10 seconds from now) with at?
– user321697
23 hours ago

1

an edit and an upvote! ;-)
– Fabby
23 hours ago

cron store tasks in crontab, right? Where does at store the scheduled data?
– user321697
23 hours ago

@user321697 Already answered here
– Fabby
23 hours ago

Sorry for reverting back your edit to the Q: you changed the OPs question's main purpose which would invalidate the simplest answer of all... ¯_(ツ)_/¯
– Fabby
23 hours ago

|
show 1 more comment

up vote
3
down vote

There is no built-in, that does the same as sleep (unless sleep is built-in). However there are some other commands that will wait.

A few include.

at and cron: used to schedule tasks at a specific time.

inotifywait: used to wait for a file, or files to be modified/removed/added/etc

edited 23 hours ago

Fabby

2,94411125

answered 23 hours ago

ctrl-alt-delor

9,96331954

There is no built-in, that does the same as sleep (unless sleep is built-in). However there are some other commands that will wait.

A few include.

at and cron: used to schedule tasks at a specific time.

inotifywait: used to wait for a file, or files to be modified/removed/added/etc

edited 23 hours ago

Fabby

2,94411125

answered 23 hours ago

ctrl-alt-delor

9,96331954

edited 23 hours ago

Fabby

2,94411125

edited 23 hours ago

Fabby

2,94411125

edited 23 hours ago

Fabby

2,94411125

answered 23 hours ago

ctrl-alt-delor

9,96331954

answered 23 hours ago

ctrl-alt-delor

9,96331954

answered 23 hours ago

ctrl-alt-delor

9,96331954

Thanks for this. Could you provide an example for performing a scheduled task (10 seconds from now) with at?
– user321697
23 hours ago

1

an edit and an upvote! ;-)
– Fabby
23 hours ago

cron store tasks in crontab, right? Where does at store the scheduled data?
– user321697
23 hours ago

@user321697 Already answered here
– Fabby
23 hours ago

Sorry for reverting back your edit to the Q: you changed the OPs question's main purpose which would invalidate the simplest answer of all... ¯_(ツ)_/¯
– Fabby
23 hours ago

|
show 1 more comment

Thanks for this. Could you provide an example for performing a scheduled task (10 seconds from now) with at?
– user321697
23 hours ago

1

an edit and an upvote! ;-)
– Fabby
23 hours ago

cron store tasks in crontab, right? Where does at store the scheduled data?
– user321697
23 hours ago

@user321697 Already answered here
– Fabby
23 hours ago

Sorry for reverting back your edit to the Q: you changed the OPs question's main purpose which would invalidate the simplest answer of all... ¯_(ツ)_/¯
– Fabby
23 hours ago

Thanks for this. Could you provide an example for performing a scheduled task (10 seconds from now) with at?
– user321697
23 hours ago

an edit and an upvote! ;-)
– Fabby
23 hours ago

cron store tasks in crontab, right? Where does at store the scheduled data?
– user321697
23 hours ago

@user321697 Already answered here
– Fabby
23 hours ago

Sorry for reverting back your edit to the Q: you changed the OPs question's main purpose which would invalidate the simplest answer of all... ¯_(ツ)_/¯
– Fabby
23 hours ago

|
show 1 more comment

up vote
2
down vote

the oldest trick in the book:

read && echo "This is a test"

Just hit Enter and it'll continue!

answered 23 hours ago

Fabby

2,94411125

This wont if the process needs to be run interaction free or in the background right?
– sai sasanka
23 hours ago

@saisasanka Deleted my superfluous comments please ping me in chat after you've done the same, so I can remove this last one... ;-)
– Fabby
22 hours ago

add a comment |

up vote
2
down vote

the oldest trick in the book:

read && echo "This is a test"

Just hit Enter and it'll continue!

answered 23 hours ago

Fabby

2,94411125

This wont if the process needs to be run interaction free or in the background right?
– sai sasanka
23 hours ago

@saisasanka Deleted my superfluous comments please ping me in chat after you've done the same, so I can remove this last one... ;-)
– Fabby
22 hours ago

add a comment |

up vote
2
down vote

the oldest trick in the book:

read && echo "This is a test"

Just hit Enter and it'll continue!

answered 23 hours ago

Fabby

2,94411125

the oldest trick in the book:

read && echo "This is a test"

Just hit Enter and it'll continue!

answered 23 hours ago

Fabby

2,94411125

answered 23 hours ago

Fabby

2,94411125

answered 23 hours ago

Fabby

2,94411125

answered 23 hours ago

Fabby

2,94411125

This wont if the process needs to be run interaction free or in the background right?
– sai sasanka
23 hours ago

@saisasanka Deleted my superfluous comments please ping me in chat after you've done the same, so I can remove this last one... ;-)
– Fabby
22 hours ago

add a comment |

This wont if the process needs to be run interaction free or in the background right?
– sai sasanka
23 hours ago

@saisasanka Deleted my superfluous comments please ping me in chat after you've done the same, so I can remove this last one... ;-)
– Fabby
22 hours ago

This wont if the process needs to be run interaction free or in the background right?
– sai sasanka
23 hours ago

@saisasanka Deleted my superfluous comments please ping me in chat after you've done the same, so I can remove this last one... ;-)
– Fabby
22 hours ago

add a comment |

up vote
2
down vote

Back in the days of microcomputers running BASIC, delays were usually accomplished with an empty loop:

FOR I = 1 TO 10000:NEXT

The same principle could be used to insert a delay in a shell script:

COUNTER=0; while [ $COUNTER -lt 10000 ]; do :; let COUNTER=COUNTER+1; done

answered 22 hours ago

Psychonaut

314212

2

A good way to make heat.
– ctrl-alt-delor
20 hours ago

Delay-loops are a terrible idea for anything except the very shortest of sleeps (a couple nanoseconds or clock cycles in a device driver) on any modern CPU that can run a Unix-like OS. i.e. a sleep so short you can't usefully have the CPU do anything else while waiting, like schedule another process or enter a low-power sleep state before waking on a timer interrupt. Dynamic CPU-frequency makes it impossible to even calibrate a delay loop for counts per second, except as a minimum delay potentially sleeping a lot longer at low clock speeds before ramping up.
– Peter Cordes
12 hours ago

Ancient computers had a power consumption that was much less dependent on workload. Modern CPUs need to dynamically power down different parts of the chip as much as possible to not melt (e.g. power down parts of the FPU or SIMD execution units while only integer code is running, or at least gate the clock signal to parts of the chip that don't need to be switching). And entering a low-power sleep state when idle (instead of spinning in an infinite loop waiting for timer interrupts) is also more recent than the ancient computers you mention.
– Peter Cordes
12 hours ago

For more about CPU history, see Modern Microprocessors A 90-Minute Guide! - lighterra.com/papers/modernmicroprocessors.
– Peter Cordes
12 hours ago

add a comment |

up vote
2
down vote

Back in the days of microcomputers running BASIC, delays were usually accomplished with an empty loop:

FOR I = 1 TO 10000:NEXT

The same principle could be used to insert a delay in a shell script:

COUNTER=0; while [ $COUNTER -lt 10000 ]; do :; let COUNTER=COUNTER+1; done

answered 22 hours ago

Psychonaut

314212

2

A good way to make heat.
– ctrl-alt-delor
20 hours ago

Delay-loops are a terrible idea for anything except the very shortest of sleeps (a couple nanoseconds or clock cycles in a device driver) on any modern CPU that can run a Unix-like OS. i.e. a sleep so short you can't usefully have the CPU do anything else while waiting, like schedule another process or enter a low-power sleep state before waking on a timer interrupt. Dynamic CPU-frequency makes it impossible to even calibrate a delay loop for counts per second, except as a minimum delay potentially sleeping a lot longer at low clock speeds before ramping up.
– Peter Cordes
12 hours ago

Ancient computers had a power consumption that was much less dependent on workload. Modern CPUs need to dynamically power down different parts of the chip as much as possible to not melt (e.g. power down parts of the FPU or SIMD execution units while only integer code is running, or at least gate the clock signal to parts of the chip that don't need to be switching). And entering a low-power sleep state when idle (instead of spinning in an infinite loop waiting for timer interrupts) is also more recent than the ancient computers you mention.
– Peter Cordes
12 hours ago

For more about CPU history, see Modern Microprocessors A 90-Minute Guide! - lighterra.com/papers/modernmicroprocessors.
– Peter Cordes
12 hours ago

add a comment |

up vote
2
down vote

Back in the days of microcomputers running BASIC, delays were usually accomplished with an empty loop:

FOR I = 1 TO 10000:NEXT

The same principle could be used to insert a delay in a shell script:

COUNTER=0; while [ $COUNTER -lt 10000 ]; do :; let COUNTER=COUNTER+1; done

answered 22 hours ago

Psychonaut

314212

Back in the days of microcomputers running BASIC, delays were usually accomplished with an empty loop:

FOR I = 1 TO 10000:NEXT

The same principle could be used to insert a delay in a shell script:

COUNTER=0; while [ $COUNTER -lt 10000 ]; do :; let COUNTER=COUNTER+1; done

answered 22 hours ago

Psychonaut

314212

answered 22 hours ago

Psychonaut

314212

answered 22 hours ago

Psychonaut

314212

answered 22 hours ago

Psychonaut

314212

2

A good way to make heat.
– ctrl-alt-delor
20 hours ago

Delay-loops are a terrible idea for anything except the very shortest of sleeps (a couple nanoseconds or clock cycles in a device driver) on any modern CPU that can run a Unix-like OS. i.e. a sleep so short you can't usefully have the CPU do anything else while waiting, like schedule another process or enter a low-power sleep state before waking on a timer interrupt. Dynamic CPU-frequency makes it impossible to even calibrate a delay loop for counts per second, except as a minimum delay potentially sleeping a lot longer at low clock speeds before ramping up.
– Peter Cordes
12 hours ago

Ancient computers had a power consumption that was much less dependent on workload. Modern CPUs need to dynamically power down different parts of the chip as much as possible to not melt (e.g. power down parts of the FPU or SIMD execution units while only integer code is running, or at least gate the clock signal to parts of the chip that don't need to be switching). And entering a low-power sleep state when idle (instead of spinning in an infinite loop waiting for timer interrupts) is also more recent than the ancient computers you mention.
– Peter Cordes
12 hours ago

For more about CPU history, see Modern Microprocessors A 90-Minute Guide! - lighterra.com/papers/modernmicroprocessors.
– Peter Cordes
12 hours ago

add a comment |

2

A good way to make heat.
– ctrl-alt-delor
20 hours ago

Delay-loops are a terrible idea for anything except the very shortest of sleeps (a couple nanoseconds or clock cycles in a device driver) on any modern CPU that can run a Unix-like OS. i.e. a sleep so short you can't usefully have the CPU do anything else while waiting, like schedule another process or enter a low-power sleep state before waking on a timer interrupt. Dynamic CPU-frequency makes it impossible to even calibrate a delay loop for counts per second, except as a minimum delay potentially sleeping a lot longer at low clock speeds before ramping up.
– Peter Cordes
12 hours ago

Ancient computers had a power consumption that was much less dependent on workload. Modern CPUs need to dynamically power down different parts of the chip as much as possible to not melt (e.g. power down parts of the FPU or SIMD execution units while only integer code is running, or at least gate the clock signal to parts of the chip that don't need to be switching). And entering a low-power sleep state when idle (instead of spinning in an infinite loop waiting for timer interrupts) is also more recent than the ancient computers you mention.
– Peter Cordes
12 hours ago

For more about CPU history, see Modern Microprocessors A 90-Minute Guide! - lighterra.com/papers/modernmicroprocessors.
– Peter Cordes
12 hours ago

A good way to make heat.
– ctrl-alt-delor
20 hours ago

Delay-loops are a terrible idea for anything except the very shortest of sleeps (a couple nanoseconds or clock cycles in a device driver) on any modern CPU that can run a Unix-like OS. i.e. a sleep so short you can't usefully have the CPU do anything else while waiting, like schedule another process or enter a low-power sleep state before waking on a timer interrupt. Dynamic CPU-frequency makes it impossible to even calibrate a delay loop for counts per second, except as a minimum delay potentially sleeping a lot longer at low clock speeds before ramping up.
– Peter Cordes
12 hours ago

Ancient computers had a power consumption that was much less dependent on workload. Modern CPUs need to dynamically power down different parts of the chip as much as possible to not melt (e.g. power down parts of the FPU or SIMD execution units while only integer code is running, or at least gate the clock signal to parts of the chip that don't need to be switching). And entering a low-power sleep state when idle (instead of spinning in an infinite loop waiting for timer interrupts) is also more recent than the ancient computers you mention.
– Peter Cordes
12 hours ago

For more about CPU history, see Modern Microprocessors A 90-Minute Guide! - lighterra.com/papers/modernmicroprocessors.
– Peter Cordes
12 hours ago

add a comment |

up vote
1
down vote

Some other ideas.

top -d10 -n2 >/dev/null



vmstat 10 2 >/dev/null



sar 10 1 >/dev/null



timeout 10s tail -f /dev/null

answered 12 hours ago

steve

13.6k22452

add a comment |

up vote
1
down vote

Some other ideas.

top -d10 -n2 >/dev/null



vmstat 10 2 >/dev/null



sar 10 1 >/dev/null



timeout 10s tail -f /dev/null

answered 12 hours ago

steve

13.6k22452

add a comment |

up vote
1
down vote

Some other ideas.

top -d10 -n2 >/dev/null



vmstat 10 2 >/dev/null



sar 10 1 >/dev/null



timeout 10s tail -f /dev/null

answered 12 hours ago

steve

13.6k22452

Some other ideas.

top -d10 -n2 >/dev/null



vmstat 10 2 >/dev/null



sar 10 1 >/dev/null



timeout 10s tail -f /dev/null

answered 12 hours ago

steve

13.6k22452

answered 12 hours ago

steve

13.6k22452

answered 12 hours ago

steve

13.6k22452

answered 12 hours ago

steve

13.6k22452

add a comment |

up vote
0
down vote

A classic from the Land of Windows and Batches:

ping -c 11 localhost >/dev/null && echo "This is a test"

answered 2 hours ago

Joker_vD

101

New contributor

add a comment |

up vote
0
down vote

A classic from the Land of Windows and Batches:

ping -c 11 localhost >/dev/null && echo "This is a test"

answered 2 hours ago

Joker_vD

101

New contributor

add a comment |

up vote
0
down vote

A classic from the Land of Windows and Batches:

ping -c 11 localhost >/dev/null && echo "This is a test"

answered 2 hours ago

Joker_vD

101

New contributor

A classic from the Land of Windows and Batches:

ping -c 11 localhost >/dev/null && echo "This is a test"

answered 2 hours ago

Joker_vD

101

New contributor

answered 2 hours ago

Joker_vD

101

New contributor

answered 2 hours ago

Joker_vD

101

answered 2 hours ago

Joker_vD

101

New contributor

Joker_vD is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment |

user321697 is a new contributor. Be nice, and check out our Code of Conduct.

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