1. 在shell文件内部定义函数并引用:
[~/shell/function]# cat factorial.sh #!/bin/bash function factorial { factorial=1 for (( i=1;i <= $1;i++ )) do factorial=$[ $factorial * $i ] done echo $1的阶乘是:$factorial } echo '程序名':$0,用于求阶乘 factorial $1 [~/shell/function]# ./factorial.sh 10
程序名:./factorial.sh,用于求阶乘
10的阶乘是:3628800
2.返回值
函数返回码是指函数最后一条命令的状态码,可以用于函数返回值
使用return命令手动指定返回值:
[~/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状态码最大是255,所以当返回值大于255时会出错。
[~/shell/function]# ./return.sh enter a: 200 print 2a: return value 144
3.函数输出
为了返回大于255的数、浮点数和字符串值,最好用函数输出到变量:
[~/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.向函数传递参数(使用位置参数):
[~/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.全局变量与局部变量
默认条件下,在函数和shell主体中建立的变量都是全局变量,可以相互引用,当shell主体部分与函数部分拥有名字相同的变量时,可能会相互影响,例如:
[~/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
在这种情况下,在函数内部最好使用局部变量,消除影响。
[~/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.向函数传递数组变量:
[~/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 ${a[*]} [~/shell/function]# ./array.sh 11 12 13 14 15 parameters : 11 12 13 14 15 360360
7.函数返回数组变量
[~/shell/function]# cat array1.sh #!/bin/bash a=(11 12 13 14 15) function array(){ echo parameters : "$@" 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