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File Permissions

File permissions are an important part of any UNIX environment. You have read, write, and execute permissions for each set of users, the owner, the files group, and everyone else on the system. If you take a long listing of a directory you can see what these permissions are set to:

bash$ ls -al
total 48
drwx------    4 bob      bob          4096 Feb 26 10:33 .
drwxr-xr-x    5 root     root         4096 Feb 26 10:33 ..
-rw-r--r--    1 bob      bob            24 Feb 26 10:33 .bash_logout
-rw-r--r--    1 bob      bob           224 Feb 26 10:33 .bash_profile
-rw-r--r--    1 bob      bob           124 Feb 26 10:33 .bashrc
-rw-r--r--    1 bob      bob          5450 Feb 26 10:33 .canna
drwxr-xr-x    2 bob      bob          4096 Feb 26 10:33 Desktop
-rw-r--r--    1 bob      bob           747 Feb 26 10:33 .emacs
drwxr-xr-x    3 bob      bob          4096 Feb 26 10:33 .kde
-rw-r--r--    1 bob      bob          3728 Feb 26 10:33 .screenrc
-r--r--r--    1 bob      bob          1019 Feb 26 10:33 .wl

In this directory the file .emacs has a string of 10 characters at the beginning of the line. The first character is where you would have information about what type of file this is. The d character stands for directory. The l character stands for symbolic link. After the first character there are nine characters left. These nine characters are split into three groups of three. The first three characters are the permissions for the owner. The next three are the permissions for the files group, and the last set of permissions are the permissions for everyone else on the system. (Everyone else on the system includes the users like apache the web server.)

Each set of three characters are split into three permissions read, write, and execute. These are marked with a letter if the permission is available or marked with a dash if the permission is not set.



Subsections
next up previous contents index
Next: Read Permissions Up: Linux Shell Environment Previous: Editors   Contents   Index
Joseph Colton 2002-09-24