shell [ trap / unset 的用法]

trap 的初步应用

#!/bin/bash

trap 'rm -f fred1' INT

touch fred1

echo "Print Ctrl + C "
while [ -f fred1 ]; do
	echo "File exist!"
	sleep 1
done

echo "the file no longer exists"

trap INT
echo create file
echo > fred1

while [ -f fred1 ]; do
	echo "File exists too!"
	sleep 1
done

echo we never get here

exit 0

unset 的初步应用

#!/bin/bash

foo="Hello World!"
echo $foo

unset foo
echo $foo

exit 0