shell---条件语句练习

1、ping主机测试,查看主机是否存活;

        脚本如下所示：

read -p "please input your hostname:" hostname
ping -c2 $hostname &> /dev/null
if [ $? = 0 ]
then
  echo "host $hostname is ok"
else
  echo "host $hostname is fail"
fi

        结果如下所示：

[[email protected] ~]# ./ping.sh 
please input your hostname:www.baidu.com
host www.baidu.com is ok
[[email protected] ~]# ./ping.sh 
please input your hostname:192.168.188.200
host 192.168.188.200 is fail
[[email protected] ~]# 

2、判断一个用户是否存在;

#!/bin/bash
##############################################################
# File Name: 2.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 16:44:24
# Description:
##############################################################

read -p "please input username:" username
grep "$username" /etc/passwd  &> /dev/null
if [ $? -eq 0 ];then
			echo "$username is already exist"
else
			echo "$username is not exist"
fi

3、判断当前内核主版本是否为3，且次版本是否大于10;

#!/bin/bash
##############################################################
# File Name: kernal_num.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 17:46:08
# Description:
##############################################################

ker_num=`uname -r | awk -F . '{print $1}'`
sec_num=`uname -r | awk -F . '{print $2}'`
if [ "$ker_num" -eq 3 ];then
	if [ "$sec_num" -le 10 ];then
		echo "the most kernel is $ker_num"		
		echo "the second version no more than 10"
	else
		echo "the most kernel is $ker_num"
		echo "the second version more than 10"
	fi
fi

4、判断vsftpd软件包是否安装，如果没有则自动安装;

#rpm -qa | grep vsftpd;echo $?
rpm -q vsftpd
#yun list vsftpd
if [ $? -eq 0 ];then
        echo "package is alread exist"
else
        echo "the package is installing"
        `yum install vsftpd` &> /dev/null
fi

5、判断httpd是否运行;  

#!/bin/bash
##############################################################
# File Name: http_jun.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 18:09:47
# Description:
##############################################################

httpd_jun=`ps -ef | grep httpd | grep -v grep | wc -l`
if [ "$httpd_jun" -ge 1 ];then
		echo "the httpd is running"
else
		echo "the httpd is not running"
fi

6、判断指定的主机是否能ping通，必须使用$1变量;

[[email protected] ~]# ./ping.sh www.baidu.com
www.baidu.com is ok
[[email protected] ~]# cat ping.sh 
#!/bin/bash
##############################################################
# File Name: ping.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 18:28:15
# Description:
##############################################################

ping -c 2 $1 &> /dev/null
if [ "$?" -eq 0 ];then
		echo "$1 is ok"
else
		echo "$1 is not ok"
fi
[[email protected] ~]#

7、报警脚本，要求如下:

        根分区剩余空间小于20%

        内存已用空间大于80%

        向用户alice发送告警邮件

        配合crond每5分钟检查一次

        [[email protected] ~]# echo "邮件正文"l mail -s"邮件主题" alice

[[email protected] ~]# cat mem.sh 
#!/bin/bash
##############################################################
# File Name: mem.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 09:31:16
# Description:
##############################################################

root_now=`df -h | grep -w / | tr -s " " | awk -F " " '{print $5}' | tr -d %`
mem_now1=`free -m | grep "^Mem:" | tr -s " " | awk -F " " '{print $3}'`
mem_now2=`free -m | grep "^Mem:" | tr -s " " | awk -F " " '{print $4}'`
mem_avg=$((mme_now1/mem_now2))
if [ "$root_now" -gt 10 ];then
		echo "the rootmemory is less than 10"
		echo "root memory now is $root_now" ; `mail -s "root_mem" root`
elif [ "$mem_avg" -gt 1 ];then
		echo "the memory is more than 1"
		echo "the memory now is $mem_avg";`mail -s "memory" root`
else
		echo "The status is right"
fi

8、判断用户输入的是否是数字，如果是数字判断该数字是否大于10;

[[email protected] ~]# cat jun__num.sh 
#!/bin/bash
##############################################################
# File Name: jun__num.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 20:44:51
# Description:
##############################################################

read -p "please input your number:" number
if echo "$number" | grep "[0-9]" &> /dev/null;then
		echo "thr number is right"
	if [ "$number" -gt 10 ];then
			echo "$number is more than 10"
	elif [ "$number" -eq 10 ];then
			echo "$number is equal 10"
	else
			echo "$number is less than 10"
	fi
fi

9、计算用户输入的任意两个整数的和、差、乘积、商、余数，

        判断用户输入的参数是否是两个，如果不是，提示用法;

        判断用户输入的是否是整数，如果不是，则给出提示终止运行。

[[email protected] ~]# cat 2.sh 
#!/bin/bash
##############################################################
# File Name: 2.sh
# Version: V1.0
# Author: xx
# Email: [email protected]
# Organization: http://www.xx.com/xx/
# Created Time : 2022-07-16 20:56:53
# Description:
##############################################################

if [ "$#" -ne 2 ];then
	echo "usage: $0 num1 num2"
	exit 1
fi
expr "$1" + "$2" &> /dev/null
if [ "$?" -ne 0 ];then
	echo "one or two is not a interger number"
	exit 2
fi
	echo "$1+$2=$(($1+$2))"
	echo "$1-$2=$(($1-$2))"
	echo "$1*$2=$(($1*$2))"
	echo "$1/$2=$(($1/$2))"
	echo "$1%$2=$(($1%$2))"