shell文本删除问题求助

请问如何使用shell脚本删除samba的配置文件中的一个用户子项啊？ samba的配置文件信息如下所示：

[global]
  workgroup = MYGROUP
  security = user

[user1]
  path = /home/user1
  public = no 
  writeable = yes  
  browseable = yes
  valid users = user1
   
[user2]
  path = /home/user2
  public = no 
  writeable = yes  
  browseable = yes
  valid users = user2

[user3]
  path = /home/user3
  public = no 
  writeable = yes  
  browseable = yes
  valid users = user3

现在需要写一个shell脚本userdel.sh， 传递一个参数， 譬如参数为user2, 执行sh userdel user2之后， 将从上面的samba配置文件中把user2的信息删除， 删除后的内容变为：
[global]
  workgroup = MYGROUP
  security = user

[user1]
  path = /home/user1
  public = no 
  writeable = yes  
  browseable = yes
  valid users = user1

[user3]
  path = /home/user3
  public = no 
  writeable = yes  
  browseable = yes
  valid users = user3

请问这个shell脚本该怎么写啊？ 哪位高手可以帮帮忙？ 万分感激！！

grep -n userN，获取所在的行号，假如获取的是10行，再用删除行sed -n '10,15p' 配置文件.ini

错了,删除是sed -n '10,15d'