param_test.sh

Linux 的shell编程小程序

#!/bin/bash
#param_test.sh
#[e-mail]
echo "1: "
A=1234
B=$A
echo $A
echo $B

echo "2: "
unset A
B=${A-2345}
echo $A
echo $B


echo "3: "
A=
B=${A-3456}
echo $A
echo $B


echo "4: "
A=
B=${A:-4567}
echo $A
echo $B

echo "5: "
A=
B=${A+5678}
echo $A
echo $B

echo "6: "
unset A
B=${A+6789}
echo $A
echo $B


echo "7: "
A=
B=${A?7890}
echo $A
echo $B

echo "8: "
unset A
B=${A?8901}
echo $A
echo $B