编写shell函数的几个方法

代码:

function functname()
{
shell commands
}

functname()
{
shell commands
}

下面是一个简单函数的脚本(ex1)示例:

代码:

message()
{
echo "message"
}

let i=1
while [ $i -le 3 ]
do
message
let i=$i+1
done

函数同样可以接受参数,$1存放第一个参数,$2存放第二个参数,$*存放输入参数的列表,...

代码:

$ more ex2
power()
{
x=$1
y=$2
count=1
result=1
while [ $count -le $y ]
do
result=`expr ${result} * $x`
count=`expr ${count} + 1`
done
echo $result
}
echo "Enter two numbers"
read num1 num2
echo -n "power is: "
power $num1 $num2

$ ex2
Enter two numbers
3 4
power is: 81

函数同样也可以返回值,使用return语句,在主程序(块)中,在调用函数之后保存返回状态$?的值.

代码:

power()
{
x=$1
y=$2
count=1
result=1
while [ $count -le $y ]
do
result=`expr ${result} * $x`
count=`expr ${count} + 1`
done
return $result
}
echo "Enter two numbers"
read num1 num2
power $num1 $num2
answer=$?
echo "$num1 to $num2 is $answer"

你也可以编写递归函数:

代码:

power()
{
x=$1
y=$2
if [ $y -eq 1 ]
then
return $x
else
y=`expr $y - 1`
power $x $y
result=`expr $? * $x`
return $result
fi
}
echo "Enter two numbers"
read num1 num2
power $num1 $num2
answer=$?
echo "$num1 to $num2 is $answer"

默认情况下,所有函数的变量都是全局变量.你可以用typeset去声明一个局部变量:

代码:

easy()
{
typeset a
a=`expr $1 + $2`
b=`expr $1 + $2`
echo "easy a is " $a
echo "easy b is " $b
}
a=10
b=20
easy $a $b
echo "global a is " $a
echo "global b is " $b

Output:
easy a is 30
easy b is 30
global a is 10
global b is 30

如果要在脚本中多次使用函数,可以把它放在一个函数目录中,像一个普通文件一样,使用的时候把它放在脚本开始的地方:
. functionfile

$ more power

代码:

power()
{
x=$1
y=$2
if [ $y -eq 1 ]
then
return $x
else
y=`expr $y - 1`
power $x $y
result=`expr $? * $x`
return $result
fi
}

$ more small
代码:

. power
echo "Enter two numbers:"
read x y
power $x $y
result=$?
echo "Answer is:" $result

$ small.ksh
2 5
Answer is: 32