流程控制：
顺序执行
选择执行
循环执行
循环执行：
将某代码段重复运行多次
重复运行多少次：
循环次数事先已知
循环次数事先未知
有进入条件和退出条件
for循环
for 变量名 in 列表;do 循环体 done
执行机制：
依次将列表中的元素赋值给“变量名”;每次赋值后即执行一次循环体;直到列表中的元素耗尽，循环结束
列表生成方式：
(1)直接给出列表
(2)整数列表：
(a){start..end}：
以start开始，end结束
{start..end..step}：
step：步长
以start开始，end结束，每次start加step,而不是加1
(b)$(seq [start [step]] end)
(3)返回列表的命令
$(COMMAND)
(4)使用glob，如：*.sh
(5)变量引用；
$@, $*
练习: 用for实现
1、判断/var/目录下所有文件的类型
#!/bin/bash #description Input /var file type #version 0.1 #author gaomeng #date 20160816 for file in /var/* ;do if [ -h $file ] ;then echo "$file is link file." elif [ -f $file ] ;then echo "$file is common file." elif [ -d $file ] ;then echo "$file is dir file" elif [ -b $file ] ;then echo "$file is block file." elif [ -c $file ] ;then echo "$file is char file." elif [ -S $file ] ;then echo "$file is socket file." elif [ -p $file ] ;then echo "$file is pipe file." else echo "$file is other file." fi done
[root@CentOS6 bin]# varfiletype.sh /var/account is dir file /var/cache is dir file /var/crash is dir file /var/cvs is dir file /var/db is dir file /var/empty is dir file /var/games is dir file /var/gdm is dir file /var/l8i8m is common file. /var/lib is dir file /var/local is dir file /var/lock is dir file /var/log is dir file /var/lte1l is common file. /var/lte4l is common file. /var/mail is link file. /var/nis is dir file /var/opt is dir file /var/preserve is dir file /var/run is dir file /var/spool is dir file /var/tmp is dir file /var/www is dir file /var/yp is dir file
2、 添加10个用户user1-user10 ，密码同用户名
#!/bin/bash
#description add 10 new users
#version 0.1
#author gaomeng
#date 20160816
for id in {1..10};do
if id user$id &> /dev/null ;then
echo "user$id is exist."
else
useradd user$id
echo user$id | passwd --stdin user$id &> /dev/null
echo "Add user$id succeed."
fi
done
[root@CentOS6 bin]# adduser10num.sh Add user1 succeed. Add user2 succeed. Add user3 succeed. Add user4 succeed. Add user5 succeed. Add user6 succeed. Add user7 succeed. Add user8 succeed. Add user9 succeed. Add user10 succeed.
3、/etc/rc.d/rc3.d 目录下分别有多个以K开头和以S开头的文件；分别读取每个文件，以K 开头的文件输出为文件加stop，以S 开头的文件输出为文件名加start；“ “K34filename stop”，“S66filename start”
#!/bin/bash #description #version 0.1 #author gaomeng #date 20160816 for file in `ls /etc/rc.d/rc3.d`;do if echo $file | grep -q "^S" ;then echo "$file start" elif echo $file | grep -q "^K" ;then echo "$file stop" fi done
[root@CentOS6 bin]# file-rc3.sh K01smartd stop K02oddjobd stop K05wdaemon stop K10psacct stop K10saslauthd stop K15htcacheclean stop S01sysstat start S02lvm2-monitor start S03vmware-tools start S08ip6tables start S10network start S11auditd start S11portreserve start
4、写一个脚本，提示输入正整数n的值，计算1+2+3+…n的总和
#!/bin/bash #desvription Input 1-N sum #version 0.1 #author gaomeng #date 20160816 read -p "Input one number: " id for num in $(seq $id) ;do let sum+=num done echo "1 and $id sum: $sum"
[root@CentOS6 bin]# sum1-N.sh Input one number: 20 1 and 20 sum: 210
5、写一个脚本，提示请输入网络地址，如192.168.0.0 ，判断输入的网段中主机在线状态
#!/bin/bash
#description
#version 0.1
#author gm
#date 20160815
#read -p "Input one ip address: " ip_addr
ip_addr=$1
echo $ip_addr | grep -qE "^(\<([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\>.){3}\<([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\>$"
if [ $? -eq 0 ];then
echo "this is a useful ip"
else
echo "this is not useful ip"
exit 20
fi
ip=`echo $ip_addr | cut -d. -f1,2,3 `
for IP in {0..255};do
ping -c1 -W1 $ip.$IP &> /dev/null && echo "$ip.$IP is up"
done
[root@CentOS6 bin]# ping-ip.sh please input one useful ip:10.1.1.0 this is a useful ip [root@CentOS6 bin]# ping-ip.sh please input one useful ip:1.1.1.1. this is not useful ip
6、打印九九乘法表
#!/bin/bash
#description Input 9*9
#version 0.1
#author gaomeng
#date 20160816
for i in {1..9};do
for j in $(seq 1 $i) ;do
echo -n -e "$j*$i=$[i*j]\t"
done
echo
done
[root@CentOS6 bin]# 9and9.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
while循环
while CONDITION; do 循环体 done
CONDITION：
循环控制条件；进入循环之前，先做一次判断
每一次循环之后会再次做判断；条件为“true” ，则执行一次循环
直到条件测试状态为“false” 终止循环
因此：CONDTION 一般应该有循环控制变量；而此变量的值会在循环体中不断地被修改
进入条件：CONDITION为true
退出条件：CONDITION为false
练习：用while实现
1 、求100 以内所有正整数之和
#!/bin/bash #description sum 1 to 100 #version 0.1 #author gaomeng #date 20160816 i=100 while [ $i -gt 0 ] ; do let sum+=i let i-- done echo "sum=$sum"
[root@CentOS6 bin]# while1-100.sh sum=5050
2 、通过ping 命令探测10.1.251.1-254 范围内的所有主机的在线状态，统计在线主机和离线主机各多少。
#!/bin/bash #description ping network ip #version 0.1 #author gaomeng #date 20160816 ip=`echo $1 | cut -d. -f1-3` i=254 while [ $i -gt 0 ] ; do ping -c1 -W1 $ip.$i &> /dev/null && let up++ let i-- done let down=254-up echo "up is $up, down is $down"
[root@CentOS6 bin]# whileping.sh 10.1.252.0 up is 32, down is 222
3、打印九九乘法表
#!/bin/bash #description Input 9*9 #version 0.1 #author gaomeng #date 20160816 i=1 while [ $i -le 9 ] ; do j=1 while [ $j -le $i ] ; do echo -ne "$j*$i=$[$j*$i]\t" let j++ done echo let i++ done
[root@CentOS6 bin]# while9and9.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
4、利用变量RANDOM 生成10 个随机数字，输出这个10 数字，并显示其中的最大者和最小者
#!/bin/bash #author goameng #version 0.2 #description: random 10 number. Input max min number #date 20160816 max=$RANDOM min=$max echo $max i=9 while [ $i -gt 0 ];do num=$RANDOM echo $num if [ $num -gt $max ];then max=$num; elif [ $num -lt $min ];then min=$num; fi let i-- done echo "max number is: $max" echo "min number is: $min"
[root@CentOS6 bin]# random.sh 32734 1975 15773 12190 25136 26654 6478 26146 23956 12014 max number is: 32734 min number is: 1975
5、打印国际象棋棋盘
#!/bin/bash #version 0.1 #author gaomeng #description pintf chess #date 20160816 i=8 while [ $i -gt 0 ];do j=8 while [ $j -gt 0 ];do sum=$[$i+$j] if `let sum%=2`;then echo -ne "\033[41m \033[0m" else echo -ne "\033[42m \033[0m" fi let j-- done echo let i-- done
until循环
until CONDITION; do 循环体 done
进入条件：CONDITION为false
退出条件：CONDITION为true
用于循环体中
循环控制语句continue
continue [N]
提前结束N层循环，而直接进入当前层+N层的循环进行条件判断；不写默认为跳过本次循环
while CONDTIITON1; do CMD1 ... if CONDITION2; then continue fi CMDn ... done
循环控制语句break
break [N]
提前跳出N层循环，不写默认为跳出当前循环
while CONDTIITON1; do CMD1 ... if CONDITION2; then break fi CMDn ... done
创建无限循环
while true; do 循环体 doneuntil false; do 循环体 Done
一、用until实现下列作业
1、每隔3秒钟到系统上获取已经登录的用户的信息；如果发现用户hacker登录，则将登录时间和主机记录于日志/var/log/login.log
#!/bin/bash
#description
#version 0.1
#author gaomeng
#date 20160816
read -p "please one username: " user
until who | grep "^$user\>" &> /dev/null ;do
sleep 3
done
echo "$user is logining system."
logintime=`date +%F-%T`
host_ip=`who | grep "^$user\>" | cut -d"(" -f2 | cut -d")" -f1`
echo "$user is login on $host_ip,time is $logintime." >> /var/log/login.log
ttynum=`who | grep "^$user\>" | tr -s ' '| cut -d' ' -f2`
until ! who | grep "^$user\>" &> /dev/null ;do
echo "please logout system." > /dev/$ttynum
sleep 1
done
echo "$user is logout system."
第1个root终端 [root@CentOS6 ~]# who root pts/0 2016-08-17 17:46 (10.1.250.25) root pts/1 2016-08-17 18:15 (10.1.250.25) [root@CentOS6 bin]# untillogin.sh please one username: gao gao is logining system. gao is logout system. 第2个root终端： [root@CentOS6 ~]# who root pts/0 2016-08-17 17:46 (10.1.250.25) root pts/1 2016-08-17 18:15 (10.1.250.25) gao pts/2 2016-08-17 18:15 (10.1.250.25) [root@CentOS6 ~]# who root pts/0 2016-08-17 17:46 (10.1.250.25) root pts/1 2016-08-17 18:15 (10.1.250.25)
普通用户终端
2、随机生成10以内的数字，实现猜字游戏，提示比较大或小，相等则退出
#!/bin/bash #description #version 0.1 #author gaomeng #date 20160816 real_num=$[$RANDOM%10] read -p "please one number on 1 to 10: " num until [ $num -eq $real_num ] ;do if [ $num -gt $real_num ] ;then echo "your number > realnum." else echo "your number < realnum." fi read -p "please one number on 1 to 10: " num done echo "you are good."
[root@CentOS6 bin]# until2.sh please one number on 1 to 10: 5 your number < realnum. please one number on 1 to 10: 8 your number > realnum. please one number on 1 to 10: 6 you are good.
3、编写脚本，求100以内所有正整数之和
#!/bin/bash #description sum 1 to 100 #version 0.1 #author gaomeng #date 20160816 i=100 until [ $i -eq 0 ] ; do let sum+=i let i-- done echo "1 to 100 sum=$sum"
[root@CentOS6 bin]# until1-100.sh 1 to 100 sum=5050
4、编写脚本，通过ping命令探测10.1.252.1-254范围内的所有主机的在线状态，统计在线主机和离线主机各多少。
#!/bin/bash #description ping network ip #version 0.1 #author gaomeng #date 20160816 ip=`echo $1 | cut -d. -f1-3` i=254 until [ $i -eq 0 ]; do ping -c1 -w1 $ip.$i &> /dev/null && let up-ip++ let i-- done let down-ip=254-upip echo "up host is $up-ip. down host is $down-ip"
[root@CentOS6 bin]# untilping.sh 10.1.252.0 up host is 23. down host is 231
5、编写脚本，打印九九乘法表
#!/bin/bash #description Input 9*9 #version 0.1 #author gaomeng #date 20160816 i=1 until [ $i -eq 10 ]; do j=1 until [ $j -gt $i ];do echo -en "$j*$i=$[$i*$j]\t" let j++ done echo let i++ done
[root@CentOS6 ~]# until9and9.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
6、编写脚本，利用变量RANDOM生成10个随机数字，输出这个10数字，并显示其中的最大者和最小者
#!/bin/bash #description random 10 number, Input max number and min number #version 0.1 #author gaomeng #date 20160816 max=$RANDOM min=$max i=9 echo "RANDOM 10 number is:" echo "$max" until [ $i -eq 0 ];do num=$RANDOM echo "$num" if [ $num -gt $max ]; then max=$num elif [ $num -lt $min ]; then min=$num fi let i-- done echo "max number is: $max . min number is $min ."
[root@CentOS6 ~]# untilrandom.sh RANDOM 10 number is: 23336 10054 3863 28020 25654 8438 31203 14681 15475 22924 max number is: 31203 . min number is 3863 .
7、编写脚本，实现打印国际象棋棋盘
#!/bin/bash #description Input chess #version 0.1 #author goameng #date 20160816 i=8 until [ $i -eq 0 ];do j=8 until [ $j -eq 0 ];do sum=$[i+j] if `let sum%=2` ;then echo -en "\033[41m \033[0m" else echo -en "\033[42m \033[0m" fi let j-- done echo let i-- done
8、打印等腰三角形
#!/bin/bash #description #version 0.1 #author gaomeng #date 20160816 read -p "please input line number: " sumline line=1 num=$sumline until [ $num -eq 0 ] ;do num1=$[sumline-line] until [ $num1 -eq 0 ]; do echo -n " " let num1-- done num2=$[2*line-1] until [ $num2 -eq 0 ]; do echo -n "*" let num2-- done echo let line++ let num-- done line=$[sumline-1] num=$[sumline-1] until [ $num -eq 0 ] ;do num1=$[sumline-line] until [ $num1 -eq 0 ]; do echo -n " " let num1-- done num2=$[2*line-1] until [ $num2 -eq 0 ]; do echo -n "*" let num2-- done echo let line-- let num-- done
[root@CentOS6 bin]# until3.sh please input line number: 4 * *** ***** ******* ***** *** * [root@CentOS6 bin]# until3.sh please input line number: 7 * *** ***** ******* ********* *********** ************* *********** ********* ******* ***** *** *
9、安装centos6.7,用centos6.8kernel升级
原内核：
[root@CentOS6 ~]# uname -r 2.6.32-642.el6.x86_64
下载kernel镜像：
[root@CentOS6 ~]# lftps cd ok, cwd=/pub lftp 10.1.0.1:/pub> cd Sources/6.x86_64/kernel(CentOS6.5)/ lftp 10.1.0.1:/pub/Sources/6.x86_64/kernel(CentOS6.5)> ls -rwxr--r-- 1 500 500 29038424 Nov 24 2013 kernel-2.6.32-431.el6.x86_64.rpm -rwxr--r-- 1 500 500 2235524 Nov 24 2013 kernel-abi-whitelists-2.6.32-431.el6.noarch.rpm -rwxr--r-- 1 500 500 9167492 Nov 24 2013 kernel-devel-2.6.32-431.el6.x86_64.rpm -rwxr--r-- 1 500 500 11015536 Nov 24 2013 kernel-doc-2.6.32-431.el6.noarch.rpm -rwxr--r-- 1 500 500 13601072 Nov 24 2013 kernel-firmware-2.6.32-431.el6.noarch.rpm -rwxr--r-- 1 500 500 2970072 Nov 24 2013 kernel-headers-2.6.32-431.el6.x86_64.rpm lftp 10.1.0.1:/pub/Sources/6.x86_64/kernel(CentOS6.5)> get kernel-2.6.32-431.el6.x86_64.rpm 29038424 bytes transferred in 2 seconds (11.13M/s) lftp 10.1.0.1:/pub/Sources/6.x86_64/kernel(CentOS6.5)> bye
安装kernel：
[root@CentOS6 ~]# rpm -ivh --force kernel-2.6.32-431.el6.x86_64.rpm Preparing... ########################################### [100%] 1:kernel ########################################### [100%]
重启电脑：
安装成功，多个内核可以在启动时选择
原创文章，作者：megedugao，如若转载，请注明出处：http://www.178linux.com/36923
