Online Manual

(Last modified Aug 26, 2002 )

The following is a simple explanation of file permissions in Unix. To list the access permissions of a file or directory, telnet to your server, then:

cd directoryname

to change the directory until you are either in the directory above the file you are interested in, or above the directory you are checking.

Type: ls -l filename

and you will see what the current permission settings are for that file, along with a bunch of other stuff.

Examples of using chmod:

People:
u = the file's user (you)
g = the file's group
o = others
a = the user, the group, and others >

Permissions:
r = read access
x = execute access
w = write access


To change permissions for a file named filename.cgi, you need to chmod the file (change mode). For example, when you type this:

chmod u=rwx,g=rx,o=rx filename.cgi

by typing this you have given:

read, execute, and write access to the user (that's you)
read and execute access to the group and;
read and execute access to others

Some scripts will tell you to chmod 775 (for example). Doing the above is the same thing as typing chmod 775. You can use either method with our Unix servers. Let me explain:

When using the numeric system, the code for permissions is as follows:

r = 4 w = 2 x = 1 rwx = 7

The first 7 of our chmod775 tells Unix to change the user's permissions to rxw (because r=4 + w=2 + x=1 adds up to 7. The second 7 applies to the group, and the last number 5, refers to others (4+1=5).

When doing an ls -l on the file, telnet always shows the permissions this way:

-rwxr-xr-x

Ignore the first dash, then break up the above into three groups of letters. If there's a dash where a letter should be, it means that there is no permission for those people.

Remember: the first 3 apply to user, the second 3 apply to group, and the third 3 apply to others.

Some FTP clients support changing permissions in a more graphical way. If you have Fetch for the Mac, you have an easy way to change permissions. Go to the file you want to change the permissions on, and highlight it. Under the Remote menu, select Change Permissions. A window will pop up showing the current permissions for the file you had highlighted. Click on the boxes to change permissions as needed.

WS_FTP accomplishes the same task as above. Just highlight the file you want to check, and right-click on it. A menu will pop up, then select CHMOD.