Linux基础知识——SHELL之循环

1、写一个脚本,判断当前系统用户shell是否都为可登陆shell(即非/sbin/nologin),分别计算两类用户的个数(通过比较字符串实现)

#!/bin/bash
#       check the user could login by default or not,and how many it is 
#       20161211
declare logini
declare nologinj
for ((i=1;i<=$(cat /etc/passwd|wc -l);i++))
do
defaultshell=$(head -$i /etc/passwd|sed $!d|cut -d: -f7)
if [ $defaultshell == /sbin/nologin ];then
logini=$(($logini+1))
else
nologinj=$(($nologinj+1))
fi
done
echo "the default login_user has $logini,the others has $nologinj"

或者

#!/bin/bash
#
#

declare nologini
declare othersj

for ((i=1;i<=$(cat /etc/passwd|wc -l);i++))
do

if [ $(head -$i /etc/passwd|sed $!d|sed s/^.*://) == /sbin/nologin ]
then
nologini=$(($nologini+1))
else
othersj=$(($othersj+1))
fi

done
echo "the default login users is $nologini,the others is $othersj"

2、写一个脚本:1)获取当前主机的主机名,保存在变量hostname中;2)判断此变量的值是否是localhost,如果是,将当前主机名更改为www.mageedu.com;3)如果不是,则显示主机名

#!/bin/bash
#   check the $HOSTNAME if its localhost,then change it to www.mageedu.com ;else display it
#   20161212

hostname=$(hostname)
if [ $hostname == localhost ] ||[ $hostname == localhost.localdomain ]
then 
hostname "www.mageedu.com"
echo -e I change HOSTNAME is $hostnamen
else
echo -e $hostname
fi

3、写一个脚本实现如下功能:1)传递一个磁盘设备文件路径给脚本,判断此设备是否存在;2)如果存在,则显示此设备上所有分区信息

#!/bin/bash
#       please input a device ,check if its a block device ,so display the partition
#

read -p "Please input a block device,like:sda、sdb:" device

if [ -b /dev/$device ]
then
echo "the $device is a block device:/dev/$device;and its partition like:"
lsblk /dev/$device
else
echo "$device is not exist!"
fi

4、写一个脚本实现以下功能:脚本能接受一个参数1)如果参数1为quit,则显示退出脚本,并执行正常退出;2)如果参数1为yes,则显示继续执行脚本;3)否则,参数1为其他任意值,均执行非正常退出

#!/bin/bash
#       while you input quit,the shell exit 0;input yes the shell continue;input other command the shell exit 1
#

read -p "please input yes,quit,*:" l 
case $l in   
yes)
echo "the shell end with no error"
exit 0
;;
quit)
echo "the shell continue"
continue
;;
*)
echo "the shell out within error"
exit 1
;;
esac

5、写一个脚本,实现以下功能,传递一个参数给脚本,此参数为gzip,bzip2或者xz三者之一:1)如果参数1的值为gzip,则使用tar和gzip归档压缩/etc目录至/backups目录中,并命名为/backups/etc-20160613.tar.gz;2)如果参数1的值为bzip2,则使用tar和bzip2归档压缩/etc目录至/backups目录中,并命名为/backups/etc-20160613.tar.bz2;3)如果参数1是xz,则使用tar和xz归档压缩/etc目录至/backups目录中,并命名为/backups/etc-20160613.tar.xz;4)如果是其他值,则显示错误的压缩工具,并执行非正常退出

#!/bin/bash
#       tar /etc/* with bzip2,gzip,xz
#


if [ $# == 0 ]
then
echo " you must choose a option(like bzip2,gzip,xz)!"
else
case $1 in

gzip)
tar -czvf /backups/etc-20161212.tar.gz /etc/*
;;
bzip2)
tar -P -cjvf /backups/etc-20161212.tar.bz2 /etc/*     
;;
xz)
tar -Jcvf /backups/etc-20161212.tar.xz /etc/*
;;
esac
ls -al /backups
fi

6、写一个脚本接受一个路径参数:1)如果是普通文件,则说明其可被正常访问;2)如果是目录文件,则说明可对其使用cd命令;3)如果是符号链接文件,则说明是个访问路径;4)其他为无法判断

#!/bin/bash
#   check the file or directory s type
#   20161213

if [ $# -eq 0 ];then
echo "you must insert a file or directory!"
elif [ -f $1 ];then
echo "$1 is a file and you can read/write it"
elif [ -d $1 ];then
echo "$1 is a directory,you can access it with COMMAND cd"
elif [ -l $1 ];then
echo "$1 is a link file"
else 
echo "i cant fond what type it is"
fi

7、写一个脚本,取得当前主机的主机名,判断1)如果主机名为空或者为localhost,或者为“(none)”,则将其命名为mailmagedu.com;2)负责,显示现有的主机名即可

同题2

8、写一个脚本,接受一个用户名为参数:1)如果用户的id号为0,则显示为管理员;2)如果用户的id号大于0且小于500,则显示其为系统用户;3)否则,显示其为普通用户

#!/bin/bash
#   check the users type,its operater or ordinery user
#   20161213

if [ $# -eq 0 ];then
echo "Please input a username!just one"
elif `id -u $1>>/dev/null 2>&1`;[ $? != 0 ];then
echo "the user $1 isnt fond" && exit 1
elif [ `id -u $1` -eq 0 ];then
echo "$1 is root"
elif [ `id -u $1` -lt 500 ];then
echo "$1 is a operator"
else
echo "$1 is a user"
fi

9、写一个脚本,传递一个用户名参数给脚本;如果用户的id号大于等于500,且其默认shell为以sh结尾的字符串,则显示“a user can log system"类的字符串

#!/bin/bash
#   check users ID greater than 500 and the last two character of the default SHELL is sh
#   20161213


if [ $# -eq 0 ];then
echo Please insert a username!
elif `id -u $1 >>/dev/null 2>&1`;[ $? != 0 ];then
echo "The user isnt fond" 
elif [ $(id -u $1) -ge 500 ] && [ $(grep $1 /etc/passwd|sed s/.*://|grep -o "sh$") == sh ];then
echo "The user $1 can login system"
else
echo "The userID is $(id -u $1),the user cannt login"
fi
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