Shell脚本day3~echo命令/数组/传递参数/基本运算符/流程控制（下）

if [条件]
then
代码
fi

a="iOS"
b="HR"
if [ $a = $b ]
then
  echo "字符串a等于字符串b"
fi

if [条件]
then
代码
else
代码
fi

a="iOS"
b="HR"
if [ $a = $b ]
then
echo "字符串a等于字符串b"
else
echo "字符串a不等于字符串b"
fi

if [条件]
then
代码
elif [条件]
then
代码
else
代码
fi

a="iOS"
b="HR"
if [ $a = $b ]
then
echo "字符串a等于字符串b"
elif [ $a ]
then
echo "字符串a不为空"
else
echo "字符串a不等于字符串b"
fi

for 变量名 in item1 item2 item3 …
do
  代码
done

for name in "a" "b" "c" "d"
do
   echo ${name}
done

for name in "I don\`t know"
do
   echo ${name}
done

value="I don\`t know"
for name in ${value}
do
   echo ${name}
done

file="/Users/wangchong/Desktop/*"
for name in ${file}
do
   echo ${name}
done

for ((a=1;a < 7; a++))
do
   echo ${a}
done

while(条件)
  do
  代码
  done

a=1
while(($a<10))
 do
  echo ${a}
  a=`expr $a + 1`
 done

a=1
while :
 do
  echo "hello"
 done

for((::))
do
  echo "hello"
done

case 值 in
  模式1)
      代码
      ;;
  模式2)
      代码
      ;;
  模式3)
      代码
      ;;
  sac

number=1
case $number in
  1) echo "等于1"
      ;;
  2) echo "等于2"
      ;;
  3) echo "等于3"
      ;;
  esac

until 条件
do
   逻辑代码
done

i=1
until (($i > 1))
do
   echo "i小于等于1"
done

for ((i=0;i<10;i++))
do
   echo "i的值是 $[i]"
   if [ $i -eq 5 ]
   then
      echo "退出循环"
   break
   fi
done

for ((i=0;i<10;i++))
do
   echo "i的值是 $[i]"
   for ((j=0;j<10;j++))
   do
      echo "j的值是 $[j]"
      if [ $j -eq 5 ]
      then
        echo "退出内层循环，i的值：$[i]，j的值：$[j]"
        break
      fi
   done
done

for ((i=0;i<10;i++))
do
   echo "i的值是 $[i]"
   for ((j=0;j<10;j++))
   do
      echo "j的值是 $[j]"
      if [ $j -eq 5 ]
      then
        echo "退出内层循环，i的值：$[i]，j的值：$[j]"
        break 2
      fi
   done
done

for ((i=0;i<5;i++))
do
  if [ $i -eq 3 ]
  then
    echo "结束当前循环的值 i=$[i]"
    continue
  fi
    echo "i的值是 $[i]"
done

i的值是 0
i的值是 1
i的值是 2
结束当前循环的值 i=3
i的值是 4