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What are File & Folder Permissions?

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  • What are File & Folder Permissions?

    Every files & folder has three permissions.
    • Read access (r)
    • Write access (w)
    • Execute access (x)


    These three permissions are defined for three types of users given blow:
    • Owner of the file or Owner
    • Groups that belongs to owner or Groups
    • Other users or All


    When we do triplet of these three users (3 types x 3 type of users), we get nine bit of information in other words we can say UNIX file permissions are nine bits of information.

    Each bit has two values
    • Set
    • Clear


    Set bit is denoted by its corresponding operation letters(r,w, or x)
    Clear bit is denoted by dash (-)

    Let me explain by this example for better understanding.

    File with this permission means -rwxr-xr-x

    The owner of the file has all permissions like read, write & execute but the group owner & rest of the user can only read & execute this file.

    File Types:

    Almost all file types are represented by preceding the permissions by one of these:
    • - = Regular File
    • d = Directory
    • l = Symbolic Link
    • b = Block Special Device
    • c = Character Device
    • s = Unix Socket (local domain socket)
    • p = Named Pipe


    See more examples to clear these file types

    File with permission: drwxr-xr-x

    In this permission "d" represent that the permissions are for directory & the owner of file has all access but other can only read & execute.


    File with permission: -rw-------

    This file permission means the owner & all access but all other & users have no access.

    Here is the octal representation of file permission

    R W X
    4 2 1

    Here 4 stands for read only, 2 stands for write only & 1 stand for execute only.

    See this table shows to check what numeric values mean:



    How to understand permissions

    644 it means owner has read & write permissions , groups & others have only read permissions.


    755 means owner has all permissions but groups & other have read & execute.

    777 means all user have all permissions.



    Read more about this in next post...............
    Last edited by Guest; 07-24-2014, 01:34 PM.

  • #2
    Hey Sonia, very edifying post its just one post and I am updated with the information, you have written it in such a way that I don’t have to read any other article on internet, It’s complete information in simple words just bookmarked your post on my laptop for future reference.

    Keep posting more!!!
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