View file mode linux

How can I get octal file permissions from command line?

There is a chmod command to set file permissions, but can I get file permissions in octal mode (such as 755) from the command line?

For people like me who accidentally landed on this page but actually were searching for how to do this on Mac: stackoverflow.com/a/14855227/470749

stat —format «%A» $FILE gives you the human readable drwxr-x— format. which may or may not be useful.

7 Answers 7

Replace * with the relevant directory or the exact filename that you want to examine.

-c --format=FORMAT use the specified FORMAT instead of the default; output a newline after each use of FORMAT %a Access rights in octal %n File name 

$ stat -c "%a %n" ./Documents/Udev.html 664 ./Documents/Udev.html 

$ stat -c "%a %n" ./Documents/ 755 ./Documents/ 

@usandfriends looping on the output of ls is a bad idea. If you really want to use a loop you can do for f in *; do stat «%a %n» «$f»; done

Why on mac os everything is slightly changed (even in unix iso utils)? Is there an actual reason of this?

@Vassilis Answer: Know. The question you’re really asking is: «if BSD came out before Linux, why did Linux change the standards instead of following the pattern set by older UNIX systems?».

File permissions in Linux can be displayed in octal format using Linux stat command.

Just press Ctrl + Alt + T on your keyboard to open Terminal. When it opens, Navigate to the directory where you want to find the file permissions in octal mode.

%A Access rights in human readable form

Octal numbers and permissions

You can use octal number to represent mode/permission:

For example, for file owner you can use octal mode as follows. Read, write and execute (full) permission on a file in octal is 0+r+w+x = 0+4+2+1 = 7

Only Read and write permission on a file in octal is 0+r+w+x = 0+4+2+0 = 6

Only read and execute permission on a file in octal is 0+r+w+x = 0+4+0+1 = 5

Use above method to calculate permission for group and others. Let us say you wish to give full permission to owner, read & execute permission to group, and read only permission to others, then you need to calculate permission as follows: User = r+w+x = 0+4+2+1 = 7 Group= r+w+x = 0+4+2+0 = 6 Others = r+w+x = 0+0+0+1 = 1

Effective permission is 761.

As detailed in “755”-style permissions with ‘ls’ by Adam Courtemanche on AgileAdam.com, you can create an alias lso that acts like ls -l but slightly processes the output 1 to display permissions also in octal. This adds a leading column showing three-digit 2 octal permissions. As written, this works for most files and directories, but it does not work properly if the sticky or setuid/setgid bits are set. 3

This has a serious shortcoming, though, as techtonik points out. You cannot pass arguments to this lso alias as you would to the ls command, because they are taken as additional arguments to awk instead. Thus you cannot run lso on a specific file or directory, nor can you pass any options (like -F , or —color ) to lso .

The fix is to define lso as a function rather than an alias.

If you’re trying this out interactively in your shell, run unalias lso to remove the alias—you can do that either before or after you define the function. If you’re putting it into a file that is sourced, such as ~/.bashrc , just take out the alias line and add the function definition.

Why does this work? Unlike aliases, bash shell functions can take positional parameters, i.e., command-line arguments. «$@» expands to the full argument list, causing arguments to the lso function to be passed to ls . (Unlike an alias definition, a function body is not quoted; hence it was necessary to remove the \ characters before $ and » .)

Since you can pass options to lso when defined this way as a function, you may wish to remove the -a and -G options from the definition—you can pass them manually in cases where you want them. (The -l option is required for details like file permissions to be shown at all, so there is no benefit to removing it.)

Thanks to techtonik for pointing out the limitation in defining lso as an alias, thus motivating me to expand this post with material about making it a function instead.

1 _{One may note this seems to flout the general rule about not parsing output from ls . ls produces very human-readable output; this introduces idiosyncrasies and limitations making it generally unsuitable as input for other commands. In this case we parse ls since we wish to preserve the exact behavior of ls except our one added change.}

2 _{One limitation of this alias, which also applies to the function version shown below it, and which may be considered a bug, is that it only displays three octal digits even when the fourth octal digit is zero. As jfmercer has rightly pointed out, the octal digits displayed here don’t reflect the sticky bit if present, nor setuid or setgid bits.}

3 _{More seriously than merely not showing the fourth octal digit is that this method assumes they are not set, and if they are—if you see t , s , or S in the permission string—then you should disregard the octal digits. This because the bits are inferred from the permissions string in a way that does not account for sticky setuid/setgid bits.}

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Linux File Permission Tutorial: How to Check and Change Permissions

Linux, like other Unix-like operating systems, allows multiple users to work on the same server simultaneously without disrupting each other.

Individuals sharing access to files pose a risk exposing classified information or even data loss if other users access their files or directories. To address this, Unix added the file permission feature to specify how much power each user has over a given file or directory.

In this tutorial, you will learn how to view and change file permissions in Linux.

How to View Check Permissions in Linux

To start with file permissions, you have to find the current Linux permission settings. There are two options to choose from, depending on your personal preference: checking through the graphical interface or using the command.

Check Permissions using GUI

Finding the file (directory) permission via the graphical user interface is simple.

1. Locate the file you want to examine, right-click on the icon, and select Properties.

2. This opens a new window initially showing Basic information about the file.
Navigate to the second tab in the window, labeled Permissions.

3. There, you’ll see that the permission for each file differs according to three categories:

• Owner (the user who created the file/directory)
• Group (to which the owner belongs to)
• Others (all other users)

For each file, the owner can grant or restrict access to users according to the categories they fall in.

In our example, the owner of the file test.txt has access to “Read and write”, while other members of its group, as well as all other users, have “Read-only” access. Therefore, they can only open the file, but cannot make any modifications.

To alter the file configuration, the user can open the drop-down menu for each category and select the desired permission.

Additionally, you can make the file executable, allowing it to run as a program, by checking the Execute box.

Check Permissions in Command-Line with Ls Command

If you prefer using the command line, you can easily find a file’s permission settings with the ls command, used to list information about files/directories. You can also add the –l option to the command to see the information in the long list format.
To check the permission configuration of a file, use the command:

For instance, the command for the previously mentioned file would be:

As seen in the image above, the output provides the following information:

• file permission
• the owner (creator) of the file
• the group to which that owner belongs to
• the date of creation.

It shows the permission settings, grouped in a string of characters (-, r, w, x) classified into four sections:

1. File type. There are three possibilities for the type. It can either be a regular file (–), a directory (d) or a link (i).
2. File permission of the user (owner)
3. File permission of the owner’s group
4. File permission of other users

The characters r, w, and x stand for read, write, and execute.
The categories can have all three privileges, just specific ones, or none at all (represented by –, for denied).

Users that have reading permission can see the content of a file (or files in a directory). However, they cannot modify it (nor add/remove files in a directory). On the other hand, those who have writing privileges can edit (add and remove) files. Finally, being able to execute means the user can run the file. This option is mainly used for running scripts.

In the previous example, the output showed that test.txt is a regular file with read and write permission assigned to the owner, but gives read-only access to the group and others.

Using Chmod Command to Change File Permissions

As all Linux users, you will at some point need to modify the permission settings of a file/directory. The command that executes such tasks is the chmod command.

chmod [permission] [file_name]

There are two ways to define permission:

1. using symbols (alphanumerical characters)
2. using the octal notation method

Define File Permission with Symbolic Mode

To specify permission settings using alphanumerical characters, you’ll need to define accessibility for the user/owner (u), group (g), and others (o).

Type the initial letter for each class, followed by the equal sign (=) and the first letter of the read (r), write (w) and/or execute (x) privileges.

To set a file, so it is public for reading, writing, and executing, the command is:

chmod u=rwx,g=rwx,o=rwx [file_name]

To set permission as in the previously mentioned test.txt to be:
• read and write for the user
• read for the members of the group
• read for other users

Use the following command:

Note: There is no space between the categories; we only use commas to separate them.

Another way to specify permission is by using the octal/numeric format. This option is faster, as it requires less typing, although it is not as straightforward as the previous method.

Instead of letters, the octal format represents privileges with numbers:

The privileges are summed up and depicted by one number. Therefore, the possibilities are:

• 7 – for read, write, and execute permission
• 6 – for read and write privileges
• 5 – for read and execute privileges
• 4 – for read privileges

As you have to define permission for each category (user, group, owner), the command will include three (3) numbers (each representing the summation of privileges).

For instance, let’s look at the test.txt file that we symbolically configured with the chmod u=rw,g=r,o=r test.txt command.

The same permission settings can be defined using the octal format with the command:

Define File Permission in Octal/Numeric Mode

Note: If you need a more in-depth guide on how to use Chmod In Linux to change file permissions recursively, read our Chmod Recursive guide.

Changing User File and Group Ownership

Aside from changing file permissions, you may come across a situation that requires changing the user file ownership or even group ownership.

Performing either of these tasks requires you first need to switch to superuser privileges. Use one of the options outlined in the previous passage.

To change the file ownership use the chown command:

chown [user_name] [file_name]

Instead of [user_name] type in the name of the user who will be the new owner of the file.

To change the group ownership type in the following command:

chgrp [group_name] [file_name]

Instead of [group_name] type in the name of the group that will be the new owner of the file.

Learning how to check and change permissions of Linux files and directories are basic commands all users should master. To change file’s group permissions, you might find helpful our article on how to use the chgrp command.

No matter whether you prefer using the GUI or command-line, this article should help you better understand how to use file permissions.

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