shell循环-for
for循环默认跳过空行，遇到空行或者空格则不会去理睬
循环分为循环次数是固定的和循环次数不是固定的，固定的有for循环，不固定的有while和until循环
for循环每次都以空格进行分隔，例如 lisi 123，本应该让i变量取一整行，结果却把lisi，123分别赋给了变量，达不到我们预期的效果，即使使用awk命令也同样只会输出lisi，123，因为$2不存在，详细请看036视频中的28分处，可以修改IFS分隔符值，让for处理文件时按回车分隔
IFS：内部字段分隔符
例如修改IFS分隔符为回车，IFS=$’\n’或者IFS’'引号中间必须有回车，否侧会处理失败
break与continue的区别
break是跳出循环
continue是跳出本次循环
1.for语法结构
shell：
for 变量名 in 取值列表
do
循环体
done
C语言风格：
for ((初值;条件;步长))
do
循环体
done
1.1批量添加网卡接口
#!/bin/bash for i do let $sum=$sum+$i done 执行./for.sh 1 2 输出3 for i后面不加东西相当于for i in $*也就是所有参数
1.1批量添加网卡接口
for i in {2..20} do ifconfig ens33:$i 192.168.81.$i done
1.2for实现批量主机ping探测
循环体中的{}&表示将循环体中的命令放到后台执行
wait命令：后台程序运行完后再执行后面的命令
#!/bin/bash #-------------------实现批量主机ping探测-------------- #20200208 >ip.txt for i in {2..254} do { ip=192.168.81.$i ping -c1 -W1 $ip &>/dev/null if [ $? -eq 0 ];then echo $ip | tee -a ip.txt fi }& done wait echo "finish........."
1.3从文件中获取ip地址进行探测
for ip in $(cat ip.txt) do ping -c1 -W1 $ip &>/dev/null if [ $? -eq 0 ];then echo "$ip is up..." else echo "$ip is down..." fi done
1.4for实现批量用户创建
#!/bin/bash #------------实现批量用户------------------- #20200208 while : do echo -en "\e[35m Please enter user prefix & user password & user numbers [zhangsan 123 10]: \e[0m" read prefix password numbers printf "user infomation: ----------------------------------------------- userprefix: $prefix userpassword: $password usernumbers: $numbers ----------------------------------------------- " read -p "Aree you sure create user[y|n|q]: " action case $action in y|Y) break ;; q) exit ;; esac done for i in $(seq -w $numbers) do user=$prefix$i id $user &>/dev/null if [ $? -eq 0 ];then echo "user $user already exists..." else useradd $user echo "$password" |passwd --stdin $user &>/dev/null if id $user &>/dev/null;then echo "user is created....." fi fi done
1.5实现从文件中批量创建用户
#!/bin/bash #------------------实现文件中批量创建用户----------------- #20200209 if [ $# -eq 0 ];then echo "usage: $(basename $0) file" exit 1 fi if [ ! -f $1 ];then echo "error file" exit 2 fi IFS=$'\n' for line in `cat $1` do user=$(echo "$line" | awk '{print $1}') pass=$(echo "$line" | awk '{print $2}') id $line &>/dev/null if [ $? -eq 0 ];then echo "$i is already exists..." else useradd $user echo "$pass" |passwd --stdin $user &>/dev/null if [ $? -eq 0 ];then echo "$i is created..." fi fi done
1.6批量创建用户改版
对比1.5主要有一下改进
1.如果用户什么都不输入则重新走一遍循环
2.如果用户输入的numbers不是整数则重新循环，并提示参数设置的不对
3.如果用户只输入了用户前缀则也重新循环
#!/bin/bash while : do echo -en "\e[36m please enter userprefix & userpassword & usernumbers: \e[0m" read userprefix userpassword usernumbers cat <<-EOF ---------------------------------------------------------------------------- user information userprefix: $userprefix userpassword: $userpassword usernumbers: $usernumbers ---------------------------------------------------------------------------- EOF if [[ ! "$usernumbers" =~ ^[0-9]+$ ]] && [ -z "$3" ];then echo -e "\e[31m error parameter\e[0m" echo -e "\e[33mPlease input again\e[0m" continue fi read -p "Are you sure user information[y|n|q]: " action case $action in y|Y) break ;; q) exit 1 esac done for i in $(seq -w $usernumbers) do user=$userprefix$i id $user &>/dev/null if [ $? -eq 0 ];then echo -e "\e[31m user $user already exists... \e[0m" else useradd $user echo "$userpassword" | passwd --stdin $user &>/dev/null if [ $? -eq 0 ];then echo -e "\e[32m $user is created....\e[0m" fi fi done
1.7根据模式进行批量用户创建和删除
1.让用户输入用户名前缀、密码、数量
2.$3必须是整数
3.将用户输入的信息打印成菜单
4.询问用户是否确认创建/删除
5.创建完成提示创建/删除成功
6.循环，用户输入的不正常则重新输入
7.如果创建则执行函数创建，删除则执行函数删除
#!/bin/bash qrxx(){ if [[ ! $usernumbers =~ ^[0-9]+$ ]];then echo -e "\e[31merror parameter\e[0m" continue fi cat <<-EOF +---------------------------------------------------------+ user information userprefix: $userprefix userpass: $userpass usernumbers: $usernumbers +---------------------------------------------------------+ EOF } create(){ echo -en "\e[034mplease enter userprefix userpass usernumbers[ user 123 10 ]: \e[0m" read userprefix userpass usernumbers qrxx echo -en "\e[35mare you sure create user infomation [y|n] \e[0m" read action case $action in y|Y) for i in `seq -w $usernumbers` do user=$userprefix$i id $user &>/dev/null if [ $? -ne 0 ];then useradd $user echo "$userpass" |passwd --stdin $user &>/dev/null if [ $? -eq 0 ];then echo "$user is created..." fi else echo "$user already exists..." fi done ;; n|N) continue ;; *) echo "error action,please input [y|n]." esac #echo "Parameter is not complete" } delete(){ echo -en "\e[034mplease enter userprefix usernumbers[ user 10 ]: \e[0m" read userprefix usernumbers qrxx echo -en "\e[35mare you sure delete user information [y|n]: \e[0m" read action case $action in y|Y) for i in $(seq -w $usernumbers) do user=$userprefix$i id $user &>/dev/null if [ $? -eq 0 ];then userdel -r $user if [ $? -eq 0 ];then echo "$user is deleted..." fi else echo "$user is not exists... " fi done ;; n|N) continue esac } while : do cat <<-EOF +---------------------------------------------------------+ | MENU | | 1.Batch to create user | | 2.Batch delete user | | q.exit | +---------------------------------------------------------+ EOF echo -en "\e[33mPlease input you want to choose the mode: \e[0m" read mode case $mode in 1) create ;; 2) delete ;; q) exit ;; *) echo "error" esac done
