WHAT IS UNIX PERMISSIONS FILES

 STEP 1:

THERE ARE THREE CLASSES OF FILE PERMISSSIONS FOR THE THREE CLASSES OF USERS:THE OWNER (OR USER) OF THE FILE.THE GROUP THE FILE BELONGS TO,AND ALL OTHER USERS OF THE SYSTEM.

$IS -1

-RWXR-XR--

THE FIRST THREE OF THE PERMISSION FIELD REFER TO THE OWNER'S PERMISSIONS;THE SECOND THREE TO THE MEMBERS OF THE FILE'S GROUP;AND THE LAST TO ANY OTHER USERS.THE FIRST THREE LETTERS,RWX,SHOW THAT THE OWNER OF THE FILE CAN READ IT,WRITE (W) IT,AND EXECUTE (X) IT.

THE SECOND GROUP OF THREE CHARACTERS,R-X,INDICATES THAT MEMBERS OF THE GROUP CAN READ AND EXECUTE THE FILE BUT CANNOT WRITE IT,THE LAST THREE CHARACTERS,R-X,SHOW THAT ALL OTHERS CAN READ AND EXECUTE THE FILE BUT NOT WRITE TO IT.

IF YOU HAVE READ PERMISSION FOR A FILE ,YOU CAN VIEW ITS CONTENTS.WRITE PERMISSION MEANS THAT YOU CAN ALTER ITS CONTENTS.EXECUTE PERMISSIONS MEANS THAT YOU CAN RUN THE FILE AS A PROGRAM.

PERMISSIONS FOR DIRECTORIES:

FOR DIRECTORIES,READ PERMISSION ALLOWS USERS TO LIST THE CONTENTS OF THE DIRECTORY,WRITE PERMISSION ALLOWS USER TO CREATE OR REMOVE FILES OR DIRECTORIES INSIDE THAT DIRECTORY,AND EXECUTE PERMISSION ALLOWS USER TO CHANGE TO THIS DIRECTORY USING THE CD COMMAND OR USE IT AS PART OF A PATHNAME.

CHANGING FILE PERMISSION:

CHMOD IS THE COMMAND TO CHANGE FILE PERMISSIONS OR DIRECTORY PERMISSIONS.

SYNTAX:

$CHMOD[WHO][+/-/=][PERMISSIONS]FILENAME

IN USING,THE FIRST SPECIFY WHICH PERMISSIONS YOU ARE CHANGING ,SECOND SPECIFY HOW THEY SHOULD BE CHANGED,THIRD,SPECIFY THE FILE PERMISSIONS TYPE.

U FOR USER OR OWNER

G FOR GROUP

O FOR OTHER

+ FOR TO ADD PERMISSIONS

-FOR TO SUBTRACT PERMISSIONS

=FOR TO ASSIGN PERMISSIONS ADD SPECIFIED PERMISSION AND TAKE AWAY ALL OTHER PERMISSIONS,IF PRESENT)

R FOR TO READ

W FOR WRITE

X FOR TO EXECUTE

EG:ADD WRITE PERMISSIONS TO GROUP MEMBERS ON TECNO FILE

$CHMOD G+W TECNO

EG2:

ADD EXECUTE PERMISSION TO OTHER AND OWNER ON TECNOSOFT FILE

$CHMOD U+X,O+X TECHNOSOFT

OR

$CHMOD UO+X TECNOSOFT

EG3:

ASSIGN READ PERMISSION TO OTHERS AND REMOVE WRITE PERMISSIONS FROMGROUP MEMBERS ON TECNOSOFT FILE

$CHMOD O=R,G-W TECNOSOFT

ANOTHER FORM OF THE CHMOD COMMAND LETS YOU SET PERMISSIONS DIRECTLY,BY USING A NUMERIC(OCTAL)CODE TO SPECIFY THEM.

THIS CODE REPRESENTS A FILE'S PERMISSIONS BY THREE OCTAL DIGITS;ONE FOR OWNER PERMISSIONS,ONE FOR GROUP PERMISSIONS,AND ONE FOR OTHERS.THESE THREE DIGITS APPEAR TOGETHER AS ONE THREE DIGIT NUMBERS.

READ=4

WRITE=2

EXECUTE=1

READ AND WRITE=6

WRITE AND EXECUTE=3

READ AND EXECUTE=5

READ,WRITE AND EXECUTE=7