Linux/Unix chmod (chmod xxx file)

Here I'm giving a brief explanation on how to changes the permission of a file in Linux/Unix system.

Syntax;

chmod [numeric number] [file]

here [numeric number] is created using the following criteria.

	owner (User who owns the file.)	group (Group that owns the file.)	anybody (Other)
non	0	0	0
read	4	4	4
write	2	2	2
execute	1	1	1

so its easy.

if you want only read by owner;

chmod 400 file

if only executed by others

chmod 001 file

if read/write by the owner and only read by everyone else

chmod (4+2)(4)(4)  file

which is;

chmod 644 file

With this if all need executable rights

chmod (4+2+1)(4+1)(4+1)  file

that's it;

chmod 755 file

This can also be calculated in a more professional way.

when we are checking the permissions of files using "ls -l" command in the terminal we get a results which looks like "- rwx r-x r-- file ".

this can be interpreted as;

- rwx r-x r-- file 

--111 101 100

here;

    r  read

    w  write

    x executable

    - non

Where now when we convert each set binary digits to decimal,

Binary Decimal 000 0 001 1 010 2 011 3

Binary Decimal 100 4 101 5 110 6 111 7

We get the numeric values we wonted. In this case its 754

So we have to use the command.

chmod 754 file