sleep.md

🔹 1. Using sleep in terminal

• Linux commands can run one after another or at the same time, but sometimes a delay is needed between commands.
• The sleep command pauses command execution for a specified time, which is useful when timing affects the correctness or success of subsequent operations.
• The command accepts delays in seconds (s), minutes (m), hours (h), or days (d), providing flexibility.
• By using sleep in scripts, users can automate tasks more effectively and prevent system overloads or command failures due to premature execution.

sleep pauses execution for a given amount of time.

Examples:

sleep 5        # sleep for 5 seconds
sleep 2m       # sleep for 2 minutes
sleep 1h       # sleep for 1 hour
sleep 0.5      # sleep for half a second

You can test it by running:

echo "Start"; sleep 3; echo "End"

👉 Output:

Start
(3 sec pause…)
End

---

🔹 2. Using sleep inside a Bash script

Example script (myscript.sh):

#!/bin/bash
echo "Step 1"
sleep 2
echo "Step 2 (after 2 seconds)"
sleep 3
echo "Step 3 (after 3 more seconds)"

Run it:

bash myscript.sh

---

🔹 3. Sleep in loops

sleep is often used inside loops to slow down execution:

#!/bin/bash
for i in {1..5}
do
    echo "Iteration $i"
    sleep 1   # wait 1 second before next iteration
done

Output:

Iteration 1
(wait 1 sec)
Iteration 2
(wait 1 sec)
...

---

🔹 4. Sleep with fractional seconds

Bash supports floating-point sleeps:

sleep 0.2   # 200 milliseconds

sleep 7h 30m && mplayer alarm.mp3

sleep 1 && echo "one" && sleep 1 && echo "two"

#!/bin/bash
SLEEP_INTERVAL="30"
CURRENT_TIME=$(date +"%T")
echo "Time before sleep: ${CURRENT_TIME}"
echo "Sleeping for ${SLEEP_INTERVAL} seconds"
sleep ${SLEEP_INTERVAL}
CURRENT_TIME=$(date +"%T")
echo "Time after sleep: ${CURRENT_TIME}"

#!/bin/bash
while :
    do
        if ping -c 1 www.google.com &> /dev/null
        then
        echo "Google is online"
        break
        fi
    sleep 10
done

while kill -0 $BACK_PID ; do
    echo "Waiting for the process to end"
    sleep 1
done

for (( i = 1 ; i <= 250 ; i++ ));
    do
    sleep 1
    qsub computation"${i}".pbs
done

References

• https://phoenixnap.com/kb/linux-sleep