File Permissions
For each file and directory in Unix there are specific permissions and an owner
set. Every file has to be owned by somebody, so whoever creates a file or
creates a folder owns that file or folder. To start off we are going to add
another switch to ls to allow us to see the owner of the file, and the
permissions.
ls -l-- This tells ls to give a _l_ong listing, displaying information about each file
Running this in my home directory yields.
dave@[datadyne]:~/$ ls -l
total 64
drwxr-xr-x 2 dave dave 4096 2010-10-04 09:33 bin/
drwxr-xr-x 3 dave dave 4096 2009-10-27 13:15 code/
drwxr-xr-x 2 dave dave 4096 2009-10-27 13:07 how to raid/
-rw-r----- 1 dave dave 12433 2010-07-28 23:57 mpd.conf
lrwxrwxrwx 1 dave dave 5 2010-07-31 11:38 opt -> /opt//
drwxr-xr-x 2 dave dave 4096 2010-08-25 16:43 pythonweb/
-rwx------ 1 dave dave 501 2010-05-19 16:29 rotate.sh
drwxr-xr-x 2 dave dave 4096 2010-10-04 09:38 sabres/
drwxr-xr-x 8 dave dave 4096 2010-07-23 09:20 scripts/
drwxr-xr-x 2 dave dave 4096 2010-06-09 17:44 temp/
drwxr-xr-x 2 dave dave 4096 2010-10-06 17:42 unix/
-rwxr-xr-x 1 dave dave 2464 2010-07-13 15:25 update.sh
drwxr-xr-x 6 dave dave 4096 2010-09-23 21:51 viridianplayer/
drwxr-xr-x 4 dave dave 4096 2010-08-04 20:03 wireless/
lrwxrwxrwx 1 dave dave 9 2010-07-31 11:38 www -> /var/www//
This is a lot of information to look at, but if we look at it column by column it's not bad. The first line just tells us how many files/folders are in the directory (it counts hidden files too). The next lines after that show us each file and information about them. The first part shows the permissions on the files. The second and third part show the username who owns it, and the group to which it's in. The next column is the file size. The next 2 columns show the modified time of the file, and the last line shows the filename.
You can set permissions on the file for the files owner, people in the group that the file is in, and everybody. A standard default permission is 755 which means the owner has read write and execute, and everybody else can only read and execute.
