#!/bin/bash
a=10
b=20
echo "a + b = `expr $a + $b`"
echo "a - b = `expr $a - $b`"
echo "a * b = `expr $a \* $b`"
echo "a / b = `expr $a / $b`"
echo "a % b = `expr $a % $b`"
if [ $a == $b ]; then
echo "a == b"
else
echo "a != b"
fi
输出:
a + b = 30
a - b = -10
a * b = 200
a / b = 0
a % b = 10
a != b
#!/bin/bash
a=10
b=20
if [ $a -eq $b ]; then
echo "a == b"
else
echo "a != b"
fi
3 逻辑运算符
运算符
说明|
&&
逻辑的 AND
||
逻辑的 OR
#!/bin/bash
a=10
b=20
if [[ $a -gt 5 && $b -le 20 ]]; then
echo "a > 5 and b <= 20"
else :
fi
4 字符串运算符
运算符
说明|
=
两个字符串是否相等
!=
两个字符串是否不相等
-z
字符串长度是否为 0
-N
字符串长度是否不为 0
str
字符串是否不为空
#!/bin/bash
a="abc"
b="edf"
c=""
if [ $a = $b ]; then
echo "$a = $b : a == b"
fi
if [ -n $a ]; then
echo "-n $a: The string $a's length is not 0"
fi
if [ !$c ]; then
echo "$c: The string $c is empty"
fi