shell 学习（四）【if语法 for循环控制】

语法：
if[ condition ] #conditon 值为true offalse
  then
   commands 代码块
fi

#!/bin/bash
#创建一个目录 假如没有就创建
if [ ! -d /opt/www ]
   then
    mkdir /opt/www
   if [ $? == 0 ] 
     then echo '创建成功'     
   else 
      echo '失败'
   fi
else
   echo '文件存在'       
fi

if  [ condition ]  
  then echo '11'
elif [ condition ]
  then echo '22'
else
  then echo '33'
fi

#1. for直接赋值
for var in 1 2 3 4 5 6 7 8 9
 do
  echo $var
  sleep 1
 done

for var in `seq 1 9`
    do
        echo $var
    done

for var in wo ai tian an men  
  do
    echo "word: $var"
  done

#!/bin/bash
if(( 100%3+1>10 ));then
  echo "yes"
else
  echo "no"
fi
for i in r1 r2 r3 cc
  do 
  if [[ $i == r* ]];then
    echo $i
  fi  
done

#!/bin/bash
echo "c格式语法"
for (( i=1;i<10;i++ ))
do
  echo  $i
done
echo "多变量c格式语法"
for (( n=0,m=10;n<10,m>0;n++,m--))
do
        echo $n*$m
done