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 |
Permission |
| u
= the file's user (you) |
r
= read access |
| g
= the file's group |
x
= execute access |
| o
= others |
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
you've 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, as in Figure 3A
below. Click on the boxes to change permissions as needed.
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