Editing Sleep (section)

== 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]