S&P 4 – loops in backgrond

Came to know recently that even loops, similar to running a command, can run on background.

Adding a "&" makes a command to run in background.                                                                     Similar to that, even loops can be run on background.

#!/bin/bash

# background-loop.sh

for i in 1 2 3 4 5 6 7 8 9 10 # First loop.

  do

    echo -n “$i “

    sleep 1 # we will need to test with this sleep and without this sleep

done & # Run this loop in background.

# Will sometimes execute after second loop.

 echo first loop # This ‘echo’ sometimes will not display.

 

 for i in 11 12 13 14 15 16 17 18 19 20 # Second loop.

    do

       echo -n “$i “

       sleep 1  # we will need to test with this sleep and without this sleep

    done

echo # This ‘echo’ sometimes will not display.

 

# ======================================================

# without the sleep 1, the expected output from the script:

# 1 2 3 4 5 6 7 8 9 10

# 11 12 13 14 15 16 17 18 19 20

 

# Sometimes, though, you get:

# 11 12 13 14 15 16 17 18 19 20

# 1 2 3 4 5 6 7 8 9 10 bozo $

# (The second ‘echo’ doesn’t execute. Why?)

 

# Occasionally also:

# 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

# (The first ‘echo’ doesn’t execute. Why?)

 

# Very rarely something like:

# 11 12 13 1 2 3 4 5 6 7 8 9 10 14 15 16 17 18 19 20

# The foreground loop preempts the background one.

exit 0

 

with that sleep 1, its really funny.