XPost: comp.unix.internals, comp.unix.questions, comp.unix.shell   
   From: eli_yardena@hotmail.com   
      
   thank you for your detailed reply.   
      
   "Anthony Borla"  wrote in message   
   news:TgeWd.185110$K7.129056@news-server.bigpond.net.au...   
   >   
   > "Eli Aran"  wrote in message   
   > news:38t75hF5ngp7hU1@individual.net...   
   >> hi there   
   >> i am learning unix on my own   
   >> i need some elaboration on the concept   
   >> of file and directory permissions.   
   >> i dont understand the concept of "others" (the third option   
   >> regarding  permissions)   
   >> who is others? how do they access the file system?   
   >> if they can effectively access the FS then are they not   
   >> assigned a group to belong to? a username and password?   
   >> in that case what is the reason for  haveing a third alternative   
   >> as "others"? how can anyone belong to "others"   
   >> and gain any type of permission to a file/directory?   
   >>   
   >   
   > [Non-technical exposition]   
   >   
   > Think of 'others' [a.k.a. 'world' group] as the set of all users [who have   
   > legitimate access to the system] who are not the superuser, not the owner   
   > [of the current file], and not in the same group as the current file. Or,   
   > put another way, permissions [to access the current file] applicable to   
   > everyone not specifically mentioned [like the file owner, or group].   
   >   
   > Since all files must have permissions, then it is vital that the   
   > permissions   
   > applicable to *all* users be specified. Assuming that there was no   
   > 'others'   
   > or 'world' group, this could be accomplished via some default mechanism   
   > [e.g. system assumes some default permission value, one probably to   
   > exclude   
   > all access]. Unfortunately, this then means that each user requiring   
   > access   
   > to a file would need to be made a member of the file's group. You can   
   > imagine, I'm sure, the maintenance headache this approach would create   
   > when   
   > considered on a system-wide basis. Also, there would be little flexibility   
   > in the types of 'permission mixes' allowed - you'd have to resort to   
   > creating 'permission sub-groups' for such things.   
   >   
   > If you think about it, use of no 'others' or 'world' group makes things   
   > much   
   > easier when the alternative is considered.   
   >   
   > I hope this helps.   
   >   
   > Anthony Borla   
   >   
   >   
      
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