shell选择和循环语句

调用脚本$();

if语句：

if[ -d ];then

xxx

else

xxx

fi

case语句：

case xxx in

xx)

xxx

;;

esac

while语句

while((xx))

do 

xxx

done

demo：

#!/bin/bash
a=$(uname -r)
echo $a
function test_if
{
if [ -d /root ];then
result=""ok""
printf "ok "
else
printf "error "
result=error
fi
}

function test_if_ret
{
printf "%s " $1
printf "%d " 0xff
}

function test_case
{
case $1 in
"ok")
printf "ok in case "
;;
"error")
printf "error in case "
;;
esac
}
function test_for
{
i=0
while((i<25))
do
echo i=$((i++))
done

}
test_if
ret_if="data"
ret_if=$(test_if_ret $result)
echo $result