#! /bin/sh

# Example to show signal handling

for (( i = 1; i < 32; ++i ))
do
    trap "echo caught signal $i" $i
done

echo My process ID is $$
echo "Now copy and paste the following into another window:"
echo 'for ((i=0;i < 32; ++i));do if ((i==9 || i==19));then let ++i;fi;echo Sending signal $i:;kill -$i '$$';sleep 1;done'
echo Then try pasting this code, and understand why this process terminates:
echo 'for ((i=0;i < 32; ++i));do echo Sending signal $i:;kill -$i '$$';sleep 1;done'

# So how can we terminate it?

# Note:
# The colon `:' is the null statement that can be used wherever the
# syntax requires a statement.  It returns the value 0 (i.e., true).
# In this case, it gives us an infinite loop.

# Try:
# $ help :

while :
do
    sleep 1
done

# Try running this in one window, and in another window, type this:
# for ((i=0;i < 32; ++i));do if ((i==9 || i==19));then let ++i;fi;echo Sending signal $i:;kill -$i 21306;sleep 1;done
# Of course, instead of 21306, put the process ID of this process.

# Then try removing the "if ((i==9 || i==19));then let ++i;fi;" statement,
# and run it again.