文件测试
数值比较
字符串比较
1、shell条件测试
格式1：test 条件表达式
格式2：[ 条件表达式 ]
格式3：[[ 条件表达式 ]]
if后面可用跟任何命令
如果想让条件为真后什么也不输出，则使用：命令，：命令=true命令
1.1文件测试
格式：[ 操作符 文件或目录 ]
选项：
[ -e dir|file ] 测试目录|文件是否存在
[ -d dir ] 测试是否为目录
[ -f file ] 测试是否为文件
[ -r file ] 测试文件是否可读—当前用户
[ -x file ] 测试文件是否可执行—当前用户
[ -w file ] 测试文件是否可写—当前用户
[ -L file ] 测试文件是否为链接文件
#-------------模拟mysql备份------------
back_dir=/back/`date +%Y%m%d`
if [ ! -d $back_dir ];then
mkdir -p $back_dir
fi
echo "开始备份..."
1.2整数比较
格式：[ 整数1 操作符 整数2 ]
选项：
[ 1 -gt 10 ] 大于
[ 1 -lt 10 ] 小于
[ 1 -eq 10 ] 等于
[ 1 -ne 10 ] 不等于
[ 1 -ge 10 ] 大于等于
[ 1 -le 10 ] 小于等于
1.2.1创建用户
read -p "please input username: " user
if id $user &>/dev/null;then
echo "user $user already exists"
exit
else
useradd $user
if [ $? -eq 0 ];then
echo "user is created..."
echo "123"|passwd --stdin $user &>/dev/null
if [ $? -eq 0 ];then
echo "Initialize the password for '123'"
fi
fi
fi
1.2.2磁盘空间告警
#!/bin/bash
=======================第一种=========================
disk_used=$(df -hT|grep '/$'|awk '{print $(NF-1)}'|awk -F "%" '{print $1}')
mail_user=jiangxiaolong
if [ $disk_used -ge 9 ];then
echo "`date +%Y-%m-%d-%X` disk / used is : ${disk_used}%" | mail -s "disk waring..." $mail_user
fi
=======================第二种=========================
disk_gen_used=$(df | grep '/$' | awk '{print $3}')
disk_gen_total=$(df | grep '/$' | awk '{print $2}')
disk_gen_percent=$(($disk_gen_used*100/$disk_gen_total))
disk_myscr_used=$(df | grep '/my_scripts' | awk '{print $3}')
disk_myscr_total=$(df | grep '/my_scripts' | awk '{print $2}')
disk_myscr_percent=$(($disk_myscr_used*100/$disk_myscr_total))
#disk_gen_content=`cat /tmp/disk_war.txt | grep -v "my_scripts"`
#disk_myscr_content=`cat /tmp/disk_war.txt | grep "my_scripts"`
gen_file=/tmp/disk_gen_war.txt
myscr_file=/tmp/disk_myscr_war.txt
rm -rf $genfile $myscr_file
if [ $disk_gen_percent -ge 90 ];then
echo "$(date +%F-%X) disk / is used: ${disk_gen_percent}%" > $gen_file
if [ -f $gen_file ];then
mail -s "disk / war.." jiangxiaolong < $gen_file
fi
rm -rf $gen_file
fi
if [ $disk_myscr_percent -ge 90 ];then
echo "$(date +%F-%X) disk /my_scripts is used: ${disk_myscr_percent}%" > $myscr_file
if [ -f $myscr_file ];then
mail -s "disk /my_scripts war..." jiangxiaolong < $myscr_file
fi
rm -rf $myscr_file
fi
1.2.3内存空间告警
#!/bin/bash
mem_used=$(free -m | grep '^Mem' |awk '{print $(NF-4)}')
mem_total=$(free -m | grep '^Mem' |awk '{print $(NF-5)}')
mem_percent=$(($mem_used*100/$mem_total))
mem_gj_file=/tmp/memory.txt
rm -rf $mem_gj_file
if [ $mem_percent -ge 80 ];then
echo "$(date +%F) memory is used: $mem_percent " > $mem_gj_file
fi
if [ -f $mem_gj_file ];then
mail -s "memory war..." jiangxiaolong < $mem_gj_file
rm -rf $mem_gj_file
fi
1.3c语言风格的数值比较
((1<2));echo $? 小于
((1==2));echo $? 等于
((1>2));echo $? 大于
((1>=2));echo $? 大于等于
((1<=2));echo $? 小于等于
((1!=2));echo $? 不等于
((`id -u`)>0);echo $? 大于
(($UID==0));echo $? 等于
1.4字符串比较
建议变量名和变量值都使用双引号，否则当变量不存在时会报语法错误
变量为空或未定义，长度都为0
[ "$USER" = "root" ];echo $?
[ "$USER" == "root" ];echo $?
BBB=""
echo ${#BBB}
0
[ -z "$BBB" ] -z用来测试字符长度是否为0
[ -n "$BBB" ] -n用来测试字符长度是否不为0
下面脚本中的一些解释
[[ ! " n u m " = [ 0 − 9 ] + num" =~ ^[0-9]+ num"= [0−9]+ ]] 双方括号用来测试正则表达式，这是表达式表示只能以0-9开头结尾的数字可以有多个，^：开头 ，$：结尾 ，+可以有多个
[[ " c o n f i r m " = [ y ∣ Y ] confirm" =~ ^[y|Y] confirm"= [y∣Y] ]] [[ " c o n f i m " = [ c r e a t e ] confim" =~ ^[create] confim"= [create] ]] [[ " c o n f i m " = [ d e l e t e ] confim" =~ ^[delete] confim"= [delete] ]]
上述三个例子是字符判断也是正则表达式，这里采用正则是为了练习，更严谨的发放是使用字符判断，例如
[ “$confim” =“create” ]
包含其中1个字符的情况下建议使用正则，多个字符同时满足则建议使用字符串比较
如果函数较长可以写到单独的文件中，然后用source命令加载即可
2.if流程控制
2.1单分支if语句结构
if 命令序列
then
fi
2.1.按套路出牌的批量创建用户
#！/bin/bash
read -p "please input number: " num
read -p "please input prefix: " prefix
for i in `seq 1 $num`
do
user=$prefix$i
useradd -M $user
echo "123"|passwd --stdin $user &>/dev/null
if [ $? -eq 0 ];then
echo "$user is created..."
fi
done
--------------------------附赠：既然可以创建那么就可以删除-------------------
read -p "please input number: " num
read -p "please input prefix: " prefix
for i in `seq 1 $num`
do
user=$prefix$i
if [ -e /home/$user ];then
userdel -r $user
else
userdel $user
fi
if [ $? -eq 0 ];then
echo "$user is delete..."
fi
done
2.1.2不按套路出牌创建用户
#!/bin/bash
-------------------创建的------------------
read -p "please input prefix: " prefix
if [ -z "$prefix" ];then
echo "error prefix"
exit
fi
read -p "please input number: " num
if [[ ! "$num" =~ ^[0-9]+$ ]];then
echo "error num"
exit
fi
read -p "Confirm to create user {prefix+num} [y/n|Y/N]:" confirm
if [[ "$confirm" =~ ^[y|Y]$ ]];then
echo "create user begin...."
elif [[ "$confirm" =~ ^[n|N]$ ]];then
echo "keep create user..."
else
echo "bye..."
fi
for i in `seq $num`
do
user=$prefix$i
useradd -M $user
echo "123"|passwd --stdin $user &>/dev/null
if [ $? -eq 0 ];then
echo "$user is created..."
fi
done
-----------------------删除的-----------------
read -p "please input prefix: " prefix
if [ -z "$prefix" ];then
echo "error prefix"
fi
read -p "please input number: " num
if [[ ! "$num" =~ ^[0-9]+$ ]];then
echo "error num"
fi
read -p "Confirm to delete user {prefix+num} [y/n|Y/N]:" confirm
if [[ "$confirm" =~ ^[y|Y]$ ]];then
echo "delete user begin...."
elif [[ "$confirm" =~ ^[n|N]$ ]];then
echo "keep delete user..."
else
echo "bye..."
fi
for i in `seq $num`
do
user=$prefix$i
if [ -e /home/$user ];then
userdel -r $user
else
userdel $user
fi
if [ $? -eq 0 ];then
echo "$user is delete..."
fi
done
2.1.3按套路出牌升级版
加了函数，让用户选择是要创建用户还是删除用户
#!/bin/bash
#-----------------批量创建用户，常规模式------------
#先将创建和删除的命令分别做成函数，在根据输入内容判断执行那个函数
usadd(){
read -p "please input prefix: " prefix
read -p "please input number: " num
for i in `seq 1 $num`
do
user=$prefix$i
useradd -M $user
echo "123"|passwd --stdin $user &>/dev/null
if [ $? -eq 0 ];then
echo "$user is created..."
fi
done
}
#--------------删用户
usdel(){
read -p "please input prefix: " prefix
read -p "please input number: " num
for i in `seq 1 $num`
do
user=$prefix$i
if [ -e /home/$user ];then
userdel -r $user
else
userdel $user
fi
if [ $? -eq 0 ];then
echo "$user is delete..."
fi
done
}
read -p "create or delete [create|delete]: " confirm
if [ "$confirm" = "create" ];then
usadd
elif [ "$confirm" = "delete" ];then
usdel
else
echo "bye!!!!!"
fi
2.1.4不按套路出牌升级版
加了函数自由选择
#!/bin/bash
################################################################
# 不按常规走，输入的不是合法的数字|前缀就退出 #
# -----------------批量创建用户，常规模式------------ #
# 根据用户输入的num和prefix，用户确认后将创建对应的用户 # #
################################################################
usadd(){
read -p "please input prefix: " prefix
if [ -z "$prefix" ];then
echo "error prefix"
exit
fi
read -p "please input number: " num
if [[ ! "$num" =~ ^[0-9]+$ ]];then
echo "error num"
exit
fi
read -p "Confirm to create user {prefix+num} [y/n|Y/N]:" confirm
if [[ "$confirm" =~ ^[y|Y]$ ]];then
echo "create user begin...."
elif [[ "$confirm" =~ ^[n|N]$ ]];then
echo "keep create user..."
else
echo "bye..."
fi
for i in `seq $num`
do
user=$prefix$i
useradd -M $user
echo "123"|passwd --stdin $user &>/dev/null
if [ $? -eq 0 ];then
echo "$user is created..."
fi
done
exit
}
################################################################
# #
# --------------删用户----------------------- #
# 根据用户输入的num和prefix，用户确认后将删除对应的用户 #
################################################################
usdel(){
read -p "please input prefix: " prefix
if [ -z "$prefix" ];then
echo "error prefix"
fi
read -p "please input number: " num
if [[ ! "$num" =~ ^[0-9]+$ ]];then
echo "error num"
fi
read -p "Confirm to delete user {prefix+num} [y/n|Y/N]:" confirm
if [[ "$confirm" =~ ^[y|Y]$ ]];then
echo "delete user begin...."
elif [[ "$confirm" =~ ^[n|N]$ ]];then
echo "keep delete user..."
else
echo "bye..."
fi
for i in `seq $num`
do
user=$prefix$i
if [ -e /home/$user ];then
userdel -r $user
else
userdel $user
fi
if [ $? -eq 0 ];then
echo "$user is delete..."
fi
done
exit
}
read -p "create or delete [create|delete]: " confirm
if [ "$confirm" = "create" ];then
usadd
elif [ "$confirm" = "delete" ];then
usdel
else
echo "bye!!!!!"
fi
2.2.if双分支语句结构
if 命令序列;then
else
fi
2.3if多分支语句结构
if 条件测试1
then 命令序列
elif 条件测试2
then 命令序列
elif 条件测试3
then 命令序列
else 命令序列
fi
2.3.1安装httpd
#!/bin/bash
www=www.baidu.com
ping -c1 $www &>/dev/null
if [ $? -eq 0 ];then
echo "check soft..."
yum list installed | grep http &>/dev/null
if [ ! $? -eq 0 ];then
echo "begin install httpd..."
yum -y install httpd
else
echo "httpd is installed..."
fi
systemctl restart httpd
systemctl enable httpd
firewall-cmd --permanent --add-service=http
firewall-cmd --permanent --add-service=https
firewall-cmd --reload
elif ping -c 192.168.81.1 &>/dev/null;then
echo "check dns..."
else
echo "check ipaddress..."
fi
systemctl status httpd &>/dev/null
if [ $? -eq 0 ];then
http_port=$(netstat -lnpt | grep http | awk '{print $4}' |awk -F':' '{print $4}')
http_address=$(netstat -lnpt | grep http | awk '{print $4}' |awk -F'80' '{print $1}')
http_pid=$(netstat -lnpt | grep http | awk '{print $(NF)}' | awk -F"/" '{print $1}')
echo "http is up..."
echo "http port is: $http_port"
echo "http listen address is: $http_address"
echo "http pid is: $http_pid"
fi
2.3.2配置yum源文件
#!/bin/bash
os_version=$(cat /etc/redhat-release | awk '{print $(NF-1)}'|awk -F"." '{print $1"."$2}')
[ ! -e /etc/yum.repos.d/bak/$(date +%F-X) ] || mkdir -p /etc/yum.repos.d/bak/$(date +%F-X)
mv /etc/yum.repos.d/* /etc/yum.repos.d/bak &>/dev/null
if [ $os_version = "7.6" ];then
cat >/etc/yum.repos.d/centos7u6.repo <<-EOF
[centos7u6]
name=centos7u6
baseurl=file:///media
enabled=1
gpgcheck=0
EOF
echo "centos $os_version yumconfig finish..."
elif [ $os_version = "6.5" ];then
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
elif [ $os_version = "5.4" ];then
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
else
echo "error osversion"
fi
