Shell编程：Linux系统环境程序设计之路

定义函数的格式
function_name(){...}
例子：
//~ fun_s
show(){
echo "show $*"
}
echo $*
echo "after function"
show c d
echo $*
exit 0
/////////////////////////////
$./fun_s a b
结果是
a b
after function
c d
a b

return：

//~ return_s
#!/bin/bash
first(){
echo "is return"
}
second(){
echo "before return"
return "0"
echo "after return"
}
return_value="$(first)"
echo $return_value
second&&echo "return 0"||echo "return other"
exit 0
//////////////////////////////////////

输出 
is return
before return
return 0

eval： 
例子：
//~ eval_s 
#!/bin/bash
var1=abcd
var2=var1
eval var3=\$$var2
echo $var3
exit 0
///////////////////////////

//~ export1_s
#!/bin/bash
var1="this is var1"
var2="this is var2"
export var2
./export2_s
exit 0
///////////////////////////

//~ export2_s
#!/bin/bash
echo "$var1"
echo "$var2"
exit 0
/////////////////////////

输出：

this is var2

#!/bin/bash
echo $var1
echo $var2
echo $var3
exit 0
//////////////////////////

//~ set-a_s
#!/bin/bash
set -a
var1="var1"
var2="var2"
var3="var3"
./set-a2_s
exit 0
//////////////////////////

//~ set-a2_s
输出：
var1
var2
var3

set：

//~ set_s
#!/bin/bash
fun1()
{
echo "a b c d"
}
set $(fun1)
echo $1
echo $(date)
set $(date)
echo $1
exit 0
///////////////////////

//~ trap_s
#!/bin/bash
trap var=2 INT
echo "please enter ctrl+c"
var=1
while [ $var = 1 ]
do
echo "in while"
sleep 1
done
exit 0
/////////////////////////