shell 函数

1 shell函数的定义及其调用

2 函数返回值

#! /bin/bash
# testing the exit status of a function
#

function func1 {
echo "This is the first form of defining a function:"
ls -l badfile   # badfile is not exist
}

func2() {
echo "This is the second form of defining a function:"
date            #
}

echo "Testing the function and exit status"
echo
func1
echo "The exit status of func1 is: $?"
echo
func2
echo "The exit status of func2 is: $?"

[root@benxintuzi shell]# ./35.sh
Testing the function and exit status

This is the first form of defining a function:
ls: cannot access badfile: No such file or directory
The exit status of func1 is: 2

This is the second form of defining a function:
Tue Aug 11 22:43:48 PDT 2015
The exit status of func2 is: 0

#! /bin/bash
# testing the exit status of a function
#

func() {
read -p "Please enter a value: " value
echo "doubling the input value..."
return $[ $value * 2 ]
}

func
echo "The exit status of func is: $?"

[root@benxintuzi shell]# ./36.sh
Please enter a value: 50
doubling the input value...
The exit status of func is: 100
[root@benxintuzi shell]# ./36.sh
Please enter a value: 200
doubling the input value...
The exit status of func is: 144

#! /bin/bash
# testing the exit status of a function
#

func() {
read -p "Please enter a value: " value
echo $[ $value * 2 ]
echo "hello, I come"
}

result=`func`
echo "The exit status of func is: $result"

[root@benxintuzi shell]# ./37.sh
Please enter a value: 500
The exit status of func is: 1000
hello, I come

3 函数参数

函数可以利用标准的环境变量参数，$0表示函数名，$1表示第一个参数，$2表示第二个参数，...，$#表示参数个数。

#! /bin/bash
# access script parameters inside a function
#

func() {
echo $[ $1 * $2 ]
}

if [ $# -eq 2 ]
then
value=`func $1 $2`
echo "The result is $value"
else
echo "Usage: func a b"
fi

[root@benxintuzi shell]# ./38.sh 55 66
The result is 3630

4 函数变量

#! /bin/bash
# local and global variable
#

func() {
local temp=$[ $value + 5 ]
result=$[ $temp * 2 ]
}

value=10
temp=20
func

echo "$temp"
echo "$result"

[root@benxintuzi shell]# ./39.sh
20
30

5 数组变量

#! /bin/bash
# array variable to function

func() {
local newarray
newarray=(`echo "$@"`)
echo "The new array value is: ${newarray[*]}"

local sum=0
for value in ${newarray[*]}
do
sum=$[ $sum + $value ]
done
echo "The sum of newarray is: $sum"
}

myarray=(1 2 3 4 5)
echo "The original array is ${myarray[*]}"
func ${myarray[*]}

[root@benxintuzi shell]# ./41.sh
The original array is 1 2 3 4 5
The new array value is: 1 2 3 4 5
The sum of newarray is: 15

#! /bin/bash
# function return array

func() {
local oriarray
local newarray
local elements
local i

oriarray=(`echo "$@"`)
newarray=(`echo "$@"`)
elements=$[ $# - 1 ]

for (( i = 0; i <= $elements; i++ ))
{
newarray[$i]=$[ ${oriarray[$i]} * 2 ]
}
echo ${newarray[*]}
}

myarray=(1 2 3 4 5)
echo "The original array is ${myarray[*]}"
arg1=`echo ${myarray[*]}`
result=(`func $arg1`)
echo "The new array is: ${result[*]}"

[root@benxintuzi shell]# ./42.sh
The original array is 1 2 3 4 5
The new array is: 2 4 6 8 10

6 创建库文件

[root@benxintuzi shell]# cat myfuncs
# my script functions

addem() {
echo $[ $1 + $2 ]
}

minusem() {
echo $[ $1 - $2 ]
}

multiem() {
echo $[ $1 * $2 ]
}

divem() {
if [ $2 -eq 0 ]
then
-1
else
echo $[ $1 / $2 ]
fi
}

[root@benxintuzi shell]# cat 40.sh
#! /bin/bash
# using functions defined in a library file

# excute library file in the context
. ./myfuncs     # source ./myfuncs

value1=10
value2=4

result1=`addem $value1 $value2`
result2=`minusem $value1 $value2`
result3=`multiem $value1 $value2`
result4=`divem $value1 $value2`

echo "addem($value1, $value2): $result1"
echo "minusem($value1, $value2): $result2"
echo "multiem($value1, $value2): $result3"
echo "divem($value1, $value2): $result4"

[root@benxintuzi shell]# ./40.sh
addem(10, 4): 14
minusem(10, 4): 6
multiem(10, 4): 40
divem(10, 4): 2

7 在命令行中使用shell函数

[root@benxintuzi shell]# addem() { val1=5; val2=10; echo $[ val1 + $val2 ]; }
[root@benxintuzi shell]# addem
15

[root@benxintuzi shell]# addem() {
> val1=5
> val2=10
> echo $[ $val1 + $val2 ]
> }
[root@benxintuzi shell]# addem
15