shell 编程for循环总结

for 变量名 in 变量取值列表；do

指令…

done

其中取值列表通常又有5种方式：

(1)直接给出列表，列表中间用空格隔开

[root@centos7 ~]#for i in 1 3 5;do echo $i;done

1

3

5

(2)整数列表

(a) {start..end}

[root@centos7 ~]#for i in {1..5..2};do echo $i;done

1

3

5

(b)$(seq start step end)

[root@centos7 ~]#for i in $(seq 1 2 5);do echo $i;done

1

3

5

(3)返回命令列表

[root@centos7 ~]#mkdir test

[root@centos7 ~]#cd test/

[root@centos7 ~/test]#touch 1.sh

[root@centos7 ~/test]#touch 3.sh

[root@centos7 ~/test]#touch 5.sh

[root@centos7 ~/test]#for i in $(ls);do echo $i;done

1.sh

3.sh

5.sh

(4)使用glob，如：*.sh

[root@centos7 ~/test]#for i in *.sh; do echo $i;done #选择当前目录下满足*.sh

1.sh

3.sh

5.sh

(5)使用变量引用如$@,$*

[root@centos7 ~/test]#vim 1

[root@centos7 ~/test]#chmod +x 1

1 #!/bin/bash

2 for i in $@;do

3 rm -rf $i

4 done

[root@centos7 ~/test]#./1 1.sh 3.sh 5.sh

[root@centos7 ~/test]#ls

1 #验证1.sh 3.sh 5.sh已经删除

for ((exp1; exp2; exp3))

do

指令

done

[root@centos7 ~/test]#for ((i=1; i<=5; i=i+2));do echo $i;done

1 #注意：a=a++ 和 a=a+2的区别，a=a+2是表达式，=号的优先级较低，因此先+后赋值

3

5

[root@centos7 ~/scripts]#vim sufakoujue.sh
#!/bin/bash
for i in $(seq 9);do
 for j in $(seq $i);do
 let sum=$i*$j
 echo -n "$j*$i=$sum "
 done
echo #打印换行，每循环一次进行一次换行
done
[root@centos7 ~/scripts]#chmod +x sufakoujue.sh
[root@centos7 ~/scripts]#./suanfakoujue.sh 
1*1=1 
1*2=2 2*2=4 
1*3=3 2*3=6 3*3=9 
1*4=4 2*4=8 3*4=12 4*4=16 
1*5=5 2*5=10 3*5=15 4*5=20 5*5=25 
1*6=6 2*6=12 3*6=18 4*6=24 5*6=30 6*6=36 
1*7=7 2*7=14 3*7=21 4*7=28 5*7=35 6*7=42 7*7=49 
1*8=8 2*8=16 3*8=24 4*8=32 5*8=40 6*8=48 7*8=56 8*8=64 
1*9=9 2*9=18 3*9=27 4*9=36 5*9=45 6*9=54 7*9=63 8*9=72 9*9=81

[root@centos7~/test]#vim panduan.sh 
 #!/bin/bash
 for filename in *;do  #利用for语句列表中第四种方式使用通配符glob
  if[ -f $filename ];then
   echo $filename is file
  else [ -d $filename ]
   echo$filename is directory
  fi
 done
[root@centos7 ~/test]#chmod+x panduan.sh 
[root@centos7 ~/test]#./panduan.sh 
1 is file
1.sh is file
2 is file
3 is directory
3.sh is file
5 is directory
5.sh is file
panduan.sh is file

[root@centos7~/test]#vim sum.sh
#!/bin/bash
 read-p "please inputyour inter: " inter
 #+++++++++++++Makesure the parameter is not empty++++++++
 [-z $inter ] && echo "you must input a inter!" && exit1
 #+++++++++++++Makesure the parameter is integer++++++++++
 if[[ $inter =~ ^[0-9]+$ ]];then
   for i in $(seq $inter);do
    let sum=$sum+i
   done
   echo"1+2+..+$i=$sum"
  else
   echo"you must input a inter!"
 fi  
[root@centos7 ~/test]#chmod+x sum.sh
[root@centos7 ~/test]#./sum.sh
please input your inter: 4
1+2+..+4=10

[root@centos7~/test]#vim 3sum.sh
#!/bin/bash
 for i in $(seq 3 3 100);do    #利用整数列表步进的方式
  let sum=$sum+i
 done
 echo "3+6+...99=$sum"
 [root@centos7 ~/test]#chmod +x 3sum.sh
[root@centos7 ~/test]#./3sum.sh 
3+6+...99=1683

[root@centos7 ~/test]#vim hostping.sh
 net=192.168.1
  for i in {1..255};do
  {
  if ping -c1 -w1 $net.$i &>/dev/null;then
  echo "$net.$i is exsit"
  fi
  }&       #通过放入后台并行执行提高执行效率，避免顺序执行
 done
 wait       #避免敲回车退出脚本，可以通过help wait查看帮助
[root@centos7 ~/test]#chmod +x hostping.sh
[root@centos7 ~/test]#./hostping.sh
192.168.1.48 is exsit

[root@centos7 ~/test]vim dengyao.sh

read -p "please input a inter: " a

for i in $(seq$a);do

let j=$a-$i+1

let k=2*$i-1

#++++++++打印每行等腰三角的空白字符+++++

for l in $(seq $j);do

echo -n " "

done

#++++++++打印等腰三角形的构成图形+++++++

for n in $(seq $k);do

echo -n ""

done

#++++++++每一行结束后进行换行+++++++++++

echo

done

[root@centos7 ~/test]./dengyao.sh