How do you view file permissions?

If you want to see the the permission of a file you can use ls -l /path/to/file command.

For example

   ls -l acroread 
   -rwxr-xr-x 1 10490 floppy 17242 May  8  2013 acroread

What does this mean ?

First - represents a regular file. It gives you a hint of the type of object it is. It can have following values.

d (directory)
c (character device)
l (symlink)
p (named pipe)
s (socket)
b (block device)
D (door)
- (regular file)

r represents read permission.
w represents write permission and
x represents executable permission.

First combination of rwx represents permission for the owner . Second combination of rwx represents permission for the group . Third combination of rwx represents permission for the other of the file.

Octal notation

Permission of file can also be represented in octal notation. In octal notation

Read or r is represented by 4, Write or w is represented by 2 Execute x is represented by 1.

Sum of these three is use to represent the permission.

stat command can be used to view file permission in octal notation

  stat -c "%a %n" /path/of/file

For example

   stat -c "%a %n" acroread 
   755 acroread

Here you can see

• For owner it is 4+2+1=7 (111 in binary)
• For group it is 4+0+1=5 (101 in binary) and
• For other it is 4+0+1=5 (101 in binary).