[~/shell/function]# cat factorial.sh 

#!/bin/bash

function factorial

{

factorial=1

for (( i=1;i <= $1;i++ ))

        do

        factorial=$[ $factorial * $i ]

        done

echo $1的階乘是:$factorial

}

echo '程序名':$0,用于求階乘

factorial $1

[~/shell/function]# ./factorial.sh 10

程序名:./factorial.sh,用于求階乘
10的階乘是:3628800

2.返回值

函數(shù)返回碼是指函數(shù)最后一條命令的狀態(tài)碼,可以用于函數(shù)返回值
使用return命令手動指定返回值：

復(fù)制代碼代碼如下:

[~/shell/function]# cat return.sh 

#!/bin/bash

function fun1 {

  read -p "enter a: " a

  echo -n "print 2a: "

  return $[ $a * 2 ]

}

fun1

echo "return value $?"

[~/shell/function]# ./return.sh 

enter a: 100

print 2a: return value 200

由于shell狀態(tài)碼最大是255，所以當(dāng)返回值大于255時(shí)會出錯(cuò)。

復(fù)制代碼代碼如下:

[~/shell/function]# ./return.sh 

enter a: 200

print 2a: return value 144

3.函數(shù)輸出

為了返回大于255的數(shù)、浮點(diǎn)數(shù)和字符串值，最好用函數(shù)輸出到變量：

復(fù)制代碼代碼如下:

[~/shell/function]# cat ./fun_out.sh 

#!/bin/bash

function fun2 {

  read -p "enter a: " a

  echo -n "print 2a: "

  echo $[ $a * 2 ]

}

result=`fun2`

echo "return value $result"

[~/shell/function]# ./fun_out.sh     

enter a: 400

return value print 2a: 800

4.向函數(shù)傳遞參數(shù)(使用位置參數(shù))：

復(fù)制代碼代碼如下:

[~/shell/function]# cat ./parameter.sh 

#!/bin/bash

if [ $# -ne 3 ]

then

    echo "usage: $0 a b c"

    exit

fi

fun3() {

    echo $[ $1 * $2 * $3 ]

}

result=`fun3 $1 $2 $3`

echo the result is $result

[~/shell/function]# ./parameter.sh  1 2 3

the result is 6

[~/shell/function]# ./parameter.sh  1 2

usage: ./parameter.sh a b c

5.全局變量與局部變量

默認(rèn)條件下，在函數(shù)和shell主體中建立的變量都是全局變量，可以相互引用，當(dāng)shell主體部分與函數(shù)部分擁有名字相同的變量時(shí)，可能會相互影響，例如:

復(fù)制代碼代碼如下:

[~/shell/function]# cat ./variable.sh    

#!/bin/bash

if [ $# -ne 3 ]

then

    echo "usage: $0 a b c"

    exit

fi

temp=5

value=6

echo temp is: $temp

echo value is: $value

fun3() {

    temp=`echo "scale=3;$1*$2*$3" | bc -ql`   

    result=$temp

}

fun3 $1 $2 $3

echo "the result is $result"

if [ `echo "$temp > $value" | bc -ql` -ne 0 ]

then 

    echo "temp is larger"

else

    echo "temp is still smaller"

fi

[~/shell/function]# ./variable.sh  12 3 2

temp is: 5

value is: 6

the result is 72

temp is larger

在這種情況下，在函數(shù)內(nèi)部最好使用局部變量，消除影響。

復(fù)制代碼代碼如下:

[~/shell/function]# cat ./variable.sh 

#!/bin/bash

if [ $# -ne 3 ]

then

    echo "usage: $0 a b c"

    exit

fi

temp=5

value=6

echo temp is: $temp

echo value is: $value

fun3() {

    local temp=`echo "scale=3;$1*$2*$3" | bc -ql`   

    result=$temp

}

fun3 $1 $2 $3

echo "the result is $result"

if [ `echo "$temp > $value" | bc -ql` -ne 0 ]

then 

    echo "temp is larger"

else

    echo "temp is still smaller"

fi

[~/shell/function]# ./variable.sh  12 3 2

temp is: 5

value is: 6

the result is 72

temp is still smaller

6.向函數(shù)傳遞數(shù)組變量：

復(fù)制代碼代碼如下:

[~/shell/function]# cat array.sh 

#!/bin/bash

a=(11 12 13 14 15)

echo ${a[*]}

function array(){

  echo parameters : "$@" 

  local factorial=1

  for value in "$@"

  do

    factorial=$[ $factorial * $value ]

  done

  echo $factorial

}

array ${a[*]}

[~/shell/function]# ./array.sh 

11 12 13 14 15

parameters : 11 12 13 14 15

360360

7.函數(shù)返回?cái)?shù)組變量

復(fù)制代碼代碼如下:

[~/shell/function]# cat array1.sh 

#!/bin/bash

a=(11 12 13 14 15)

function array(){

  echo parameters : "$@" 

  local newarray=(`echo "$@"`)

  local element="$#"

  local i

  for (( i = 0; i < $element; i++ ))

  {

    newarray[$i]=$[ ${newarray[$i]} * 2 ]    

  }

  echo  new value:${newarray[*]}

}

result=`array ${a[*]}`

echo ${result[*]}

[~/shell/function]# ./array1.sh 

parameters : 11 12 13 14 15 new value:22 24 26 28 30