Editing Sleep

Sleep random seconds in programming

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== MS-DOS on Windows ==
=== Approach 1: %RANDOM% + ping local ===
Purpose
* Sleep random seconds between 5 ~ 60 seconds

BAT file:
<syntaxhighlight lang="Windows batch files">
REM print current date & time
ECHO %date% %time%

REM sleep 5 ~ 60 seconds
SET /a timeout=%RANDOM% * 55 / 32767 + 5
ping 127.0.0.1 -n %timeout% > nul

REM print current date & time
ECHO %date% %time%
</syntaxhighlight>

Instruction<ref>[https://stackoverflow.com/questions/8258087/bat-random-timeout batch file - .bat random timeout - Stack Overflow]</ref>
* {{kbd | key=<nowiki>%RANDOM%</nowiki>}} returns an integer between 0 and 32767<ref>[https://ss64.com/nt/syntax-random.html Random Numbers - Windows CMD - SS64.com]</ref>.
* 55 is the range of values you want: 5 to 60.
* 32767 is the range of values returned by {{kbd | key=<nowiki>%RANDOM%</nowiki>}} (0 to 32767).
* 5 is the minimum value you want. The original range of values is '0 to 55'. After plus 5 the range became '5 ~ 65'.
* ping local address: {{kbd | key=<nowiki>/n <Count></nowiki>}} "Specifies the number of echo Request messages sent. The default is 4."<ref>[https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/ping time]</ref><ref>[https://stackoverflow.com/questions/735285/how-to-wait-in-a-batch-script windows xp - How to wait in a batch script? - Stack Overflow]</ref>

=== Approach 2: sleep package of CygWin ===
Requirement: Install [https://cygwin.com/install.html Cygwin] on {{Win}} & install {{kbd | key=<nowiki>sleep</nowiki>}} package (How-to: [https://x.cygwin.com/docs/ug/setup.html Setting Up Cygwin/X])

Verify the installation of {{kbd | key=<nowiki>sleep</nowiki>}} package<ref>[https://stackoverflow.com/questions/9260014/how-do-i-install-cygwin-components-from-the-command-line How do I install cygwin components from the command line? - Stack Overflow]</ref><ref>[http://polarhome.com/service/man/?qf=SLEEP&af=0&tf=2&of=Cygwin SLEEP man page on Cygwin]</ref>
# Key-in {{kbd | key=<nowiki>cmd</nowiki>}} to open command prompt ([https://www.lifewire.com/how-to-open-command-prompt-2618089 How to Open Command Prompt (Windows 10, 8, 7, Vista, XP)])
# Key-in one of following commands
#* Key-in {{kbd | key=<nowiki>where sleep</nowiki>}} if you add installation path of CygWin to system path ([[How to setup my system path]]). Or
#* Key-in {{kbd | key=<nowiki>dir C:\cygwin64\bin\sleep.exe</nowiki>}} if the installation path of CygWin is {{kbd | key=<nowiki>C:\cygwin64\</nowiki>}}.
<pre>
C:\Users\user>dir C:\cygwin64\bin\sleep.exe

# successful condition
C:\cygwin64\bin\sleep.exe

# failed condition
File Not Found
</pre>

BAT file:
<pre>
REM print current date & time
ECHO %date% %time%

REM sleep 5 ~ 60 seconds
SET /a timeout=%RANDOM% * 55 / 32767 + 5
C:\cygwin64\bin\sleep.exe %timeout%

REM print current date & time
ECHO %date% %time%
</pre>

=== Approach 3: TIMEOUT ===
Alternative command: {{exclaim}} The following command {{kbd | key=<nowiki>ECHO %date% %time%</nowiki>}} will not be executed after {{kbd | key=<nowiki>TIMEOUT %timeout%</nowiki>}} was executed.

BAT file:
<pre>
SET /a timeout=%RANDOM% * 55 / 32767 + 5
TIMEOUT %timeout%

ECHO %date% %time%
</pre>

== BASH ==

=== Approach1: sleep ===
Tested on {{Linux}} & {{Mac}}<ref>[https://bash.cyberciti.biz/guide/Perform_arithmetic_operations Perform arithmetic operations - Linux Shell Scripting Tutorial - A Beginner's handbook]</ref><ref>[https://linuxize.com/post/how-to-use-linux-sleep-command-to-pause-a-bash-script/ Linux Sleep Command (Pause a Bash Script) | Linuxize]</ref>
<pre>
# print current date & time
echo $(date '+%Y-%m-%d %H:%M:%S')

# sleep 5 ~ 65 seconds
timeout=$(($RANDOM * 60 / 32768 + 5))
sleep $timeout

# print current date & time
echo $(date '+%Y-%m-%d %H:%M:%S')
</pre>

Sleep couple [https://en.wikipedia.org/wiki/Microsecond microsecond]s<ref>[https://serverfault.com/questions/151109/how-do-i-get-the-current-unix-time-in-milliseconds-in-bash How do I get the current Unix time in milliseconds in Bash? - Server Fault]</ref>. Tested on {{Linux}}

<pre>
# print current unix timestamp e.g. 1598346362244
date +%s%N

# sleep 1 millisecond = 0.001 seconds
sleep 0.001s

# print current unix timestamp
date +%s%N
</pre>


Sleep couple microseconds. Tested on {{Mac}}

<pre>
# print current unix timestamp e.g. 1598346362244
php -r 'echo microtime(TRUE) . PHP_EOL;'

# sleep 1 millisecond = 0.001 seconds
sleep 0.001s

# print current unix timestamp
php -r 'echo microtime(TRUE) . PHP_EOL;'
</pre>


Sleep couple microseconds. Tested on {{Mac}}

<pre>
# print current unix timestamp e.g. 1598346362244
Sleep couple microseconds. Tested on {{Mac}}

<pre>
# print current unix timestamp e.g. 1598346362244
php -r 'echo microtime(TRUE) . PHP_EOL;'

# sleep 1 millisecond = 0.001 seconds
sleep 0.001s

# print current unix timestamp
php -r 'echo microtime(TRUE) . PHP_EOL;'
</pre>


Sleep couple milliseconds (1 seconds = 1000 milliseconds) e.g. 1671090194.136471987<ref>[https://apple.stackexchange.com/questions/135742/time-in-milliseconds-since-epoch-in-the-terminal macos - Time in milliseconds since epoch in the terminal - Ask Different]</ref>
<pre>
# print current unix timestamp in milliseconds e.g. 1671090194.136471987
perl -MTime::HiRes=time -e 'printf "%.9f\n", time'

# sleep 1 millisecond = 0.001 seconds
sleep 0.001s

# print current unix timestamp
perl -MTime::HiRes=time -e 'printf "%.9f\n", time'
</pre>

=== Approach2: ping ===
Tested on {{Linux}} & {{Mac}}

ping local address: {{kbd | key=<nowiki>-c <Count></nowiki>}} "Stop after sending (and receiving) count ECHO_RESPONSE packets."<ref>[https://linux.die.net/man/8/ping ping(8) - Linux man page]</ref>

<pre>
# print current date & time
echo $(date '+%Y-%m-%d %H:%M:%S')

# sleep 5 ~ 65 seconds
timeout=$(($RANDOM * 60 / 32768 + 5))
ping 127.0.0.1 -c $timeout > nul

# print current date & time
echo $(date '+%Y-%m-%d %H:%M:%S')
</pre>

=== Approach3: usleep ===
[https://linux.die.net/man/3/usleep usleep(3) - Linux man page] "suspend execution for microsecond intervals" (1 second = 1 000 000 microsecond). Tested on {{Linux}}

<pre>
# print current date, time & nanoseconds
echo $(date '+%Y-%m-%d %H:%M:%S')$(date '+.%N')

# sleep 0.2 ~ 1.2 seconds
timeout=$(($RANDOM * 1000000 / 32768 + 200000))
echo $timeout
usleep $timeout

# print current date, time & nanoseconds
echo $(date '+%Y-%m-%d %H:%M:%S')$(date '+.%N')

</pre>

=== BASH example: download file and sleep random seconds between 1 ~ 7 seconds ===

The following script checks if a specific file exists in a defined path. If the file doesn't exist, it downloads the file from a provided URL and then pauses for a random duration between 1 and 7 seconds. If the file already exists, it simply prints a message stating that the file was found and the download was skipped.

<pre>
if [ ! -f /path/to/paper.pdf ]
then
    curl "https://website/to/pdf" -L -o /path/to/paper.pdf
    sleep $((1 + RANDOM % 7))
else
    echo "File found. Download skipped."
fi
</pre>

The same command can be written on one line:
<pre>
if [ ! -f /path/to/paper.pdf ]; then curl "https://website/to/pdf" -L -o /path/to/paper.pdf; sleep $((1 + RANDOM % 7)); else echo "File found. Download skipped."; fi
</pre>

References

* [https://www.cyberciti.biz/faq/bash-check-if-file-does-not-exist-linux-unix/ How to check if file does not exist in Bash - nixCraft]

== PHP ==
* [http://php.net/manual/en/function.sleep.php PHP: sleep - Manual]
* [http://php.net/manual/en/function.usleep.php PHP: usleep - Manual]

== JavaScript ==
* [https://www.w3schools.com/js/js_timing.asp JavaScript Timing Events]
* [https://www.educative.io/edpresso/what-is-the-javascript-alternative-to-the-sleep-function What is the Javascript alternative to the sleep function?]

== References ==

<References />

== Related ==

* [https://en.wikipedia.org/wiki/Sleep_(system_call) Sleep (system call) - Wikipedia]
* [https://blog.gtwang.org/windows/excel-random-number-generation-formula/ Excel 產生各種亂數的公式整理與函數教學 - G. T. Wang]
* [https://blog.miniasp.com/post/2009/06/24/Sleep-command-in-Batch 如何在批次檔(Batch)中實現 sleep 命令讓任務暫停執行 n 秒 | The Will Will Web]
* [https://errerrors.blogspot.com/2024/02/implement-randbetween-using-round.html Excel 使用 RAND 函數實作 RANDBETWEEN 函數]

[[Category:Programming]] [[Category:PHP]] [[Category:MS-DOS]] [[Category:Bash]] [[Category:Tool]]