shell脚本编程-例子_批量添加用户脚本

用户管理是Linux系统维护的工作之一，其中设计用户添加、删除等简单操作.

需求：一次添加很多用户.在一个文本文件中.

格式：以行为单位，每行是一条用户信息.用户名和密码之间使用特定的分隔符分开，可是是空格，逗号，Tab键等。这里用空格区分

eg:

[rhat@localhost ~]$ cat addusers.txt 
username001 password001
username002 password002
username003 password003
username004 password004
usernmae005 paswword005

按行读取文件中用户信息.可以用for、while、until循环等.这里先暂时用for循环.

[rhat@localhost ~]$ vim useradd_for01.sh
[rhat@localhost ~]$ cat useradd_for01.sh 
#!/bin/bash
COUNT=0
for LINES in `cat addusers.txt`
do
    echo $LINES
    let COUNT+=1
done
echo
echo "$0 looped $COUNT times"
[rhat@localhost ~]$ sh ./useradd_for01.sh 
username001
password001
username002
password002
username003
password003
username004
password004
usernmae005
paswword005

./useradd_for01.sh looped 10 times

以上按理说应该循环5次，可为什么循环了10次？，原来addusers.txt是用空格隔开的，而for循环在读取文件时，任何空白字符都可以作为其读取的分隔符.下面是while循环的例子：

[rhat@localhost ~]$ vim useradd_while01.sh
[rhat@localhost ~]$ cat useradd_while01.sh 
#!/bin/bash
COUNT=0
while read LINES
do
    echo $LINES
    let COUNT+=1
done < addusers.txt
echo
echo "$0 looped $COUNT times"
[rhat@localhost ~]$ sh ./useradd_while01.sh 
username001 password001
username002 password002
username003 password003
username004 password004
usernmae005 paswword005

./useradd_while01.sh looped 5 times

从脚本运行结果来看，while的按行读取确实没有问题，因为while使用是换行符作为标记。（read 命令）

加工：从每行中分割出用户名和密码，每行空格前部分是用户名，空格后的部分为密码。值需要使用cut命令就能进行简单的拆分.

[rhat@localhost ~]$ vim useradd_while02.sh 
[rhat@localhost ~]$ cat useradd_while02.sh 
#!/bin/bash
while read LINES
do
    USERNAME=`echo $LINES | cut -f1 -d' '`
    USERPASS=`echo $LINES | cut -f2 -d' '`
    echo -n "USERNAME:$USERNAME PASSWORD:$USERPASS"
    echo
done < addusers.txt

[rhat@localhost ~]$ sh ./useradd_while02.sh 
USERNAME:username001 PASSWORD:password001
USERNAME:username002 PASSWORD:password002
USERNAME:username003 PASSWORD:password003
USERNAME:username004 PASSWORD:password004
USERNAME:usernmae005 PASSWORD:paswword005

 其中运行passwd命令时，需要手动输入密码，可以通过man passwd 观察到 --stdin这个选项可以将密码用管道“|“传送密码.

--stdin
　　　　This option is used to indicate that passwd should read the  new  password from standard input, which can be a pipe.

脚本修改后如下：（需要root权限）

[root@localhost rhat]# cat useradd_while03.sh 
#!/bin/bash
while read LINES
do
    USERNAME=`echo $LINES | cut -f1 -d' '`
    USERPASS=`echo $LINES | cut -f2 -d' '`
    useradd $USERNAME
    echo $USERPASS | passwd --stdin $USERNAME
done < addusers.txt
[root@localhost rhat]# sh ./useradd_while03.sh 
Changing password for user username001.
passwd: all authentication tokens updated successfully.
Changing password for user username002.
passwd: all authentication tokens updated successfully.
Changing password for user username003.
passwd: all authentication tokens updated successfully.
Changing password for user username004.
passwd: all authentication tokens updated successfully.
Changing password for user usernmae005.
passwd: all authentication tokens updated successfully.

以上脚本”可以工作“了，但还不是很完美,再运行一便，会发现新增用户不行了。但却又重修修改了密码.这是很危险的.应该增加一个用户是否存在的判断.另外所有非Shell内建命令都建议使用全路径，以避免由于环境变量的问题造成command not found。最后，脚本主体要尽量少使用变量，所以需要在脚本开头定义变量.如下：

[root@localhost rhat]# vim useradd_while04.sh
[root@localhost rhat]# cat useradd_while04.sh 
#!/bin/bash
USER_INFO=/home/rhat/addusers.txt
USERADD=/usr/sbin/useradd
PASSWD=/usr/bin/passwd
CUT=/bin/cut
while read LINES
do
    USERNAME=`echo $LINES | $CUT -f1 -d' '`
    USERPASS=`echo $LINES | $CUT -f2 -d' '`
    $USERADD $USERNAME
    if [ $? -ne 0 ];then
        echo "$USERNAME exists,skip set password"
    else    
        echo $USERPASS | $PASSWD --stdin $USERNAME
    fi
done < $USER_INFO
[root@localhost rhat]# sh ./useradd_while04.sh 
useradd: user 'username001' already exists
username001 exists,skip set password
useradd: user 'username002' already exists
username002 exists,skip set password
useradd: user 'username003' already exists
username003 exists,skip set password
useradd: user 'username004' already exists
username004 exists,skip set password
useradd: user 'usernmae005' already exists
usernmae005 exists,skip set password

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