Building 3D Models for the Web

Setting File Permissions in Unix

The SGI workstations and the DECstations use variations of the Unix operating system. You need to set access permissions on your Web files so that everyone can read them. If you are working in groups, then you also have to set permissions so that the others in your group can modify your files.

Determining Access Permissions

You can view the access permissions on your files using the command

    jaguar 1% ls -l

That's an ell, not a one after the hyphen. The output will look something like this.

    -rw-r--r--    1 jbhkvwa  iupsouth        362 Mar 29 20:47 nontrdbse.wrl
    -rw-rw-r--    1 mmccarty iupsouth        771 Mar 16 17:39 nontrdhse.html
    drwxrwxr-x    2 mmccarty ls499          4096 Mar 29 21:01 objects

The first character indicates the type of file. A hyphen indicates a regular file and a "d" indicates a directory. In the example above, nontrdbse.wrl and nontrdhse.html are regular files and objects is a directory.
The next three characters indicate the access for the file owner. The three characters represent read access, write access, and execute access. You have to have write access to change or delete the file. For directories, read access means that you can use the ls command to list the files in the directory. Execute access for directories means that you can cd to the directory. In the example above, the owner jbhkvwa has read and write access to nontrdbse.wrl and the owner mmccarty has read and write access to nontrdhse.html. The owner mmccarty has read, write, and execute access to the objects directory.
The next three characters indicate the group access. In the example, the group iupsouth has read access to nontrdbse.wrl and read and write access to nontrdhse.html. The ls499 group has read, write, and execute access to the objects directory. If you are working on a group project, then the group should have read and write access to regular files and read, write, and execute access to directories.
The last three characters in the access list indicate others' access. In the example, everyone has read access to both files and read and execute access to the directory. If you are publishing files on the Internet, then others should have read access to regular files and read and execute access to directories.

Changing Access Permissions

If you are working on a group project, you need to change the group ownership of your files and directories.

    jaguar 3% chgrp iupsouth objects

You can change the group ownership for all of the files in the current directory by using an asterisk

    jaguar 4% chgrp iupsouth *

Use the chmod command to change access permissions. The chmod command has two forms--a comprehensible form and a bizarro form. The comprehensible form is

    jaguar 4% chmod g+r nontrdbse.wrl

This adds read access for the group. Use u for the owner (or user), g for the group, o for others, and a for all three. You can combine them.

    jaguar 4% chmod go+r nontrdbse.wrl
    jaguar 5% chmod go+rx objects
    jaguar 6% chmod g+rw,o+r nontrdbse.wrl

The bizarro form uses numbers to set access permissions.

    Digit Access
    ----- ------
      0    ---
      4    r--
      5    r-x
      6    rw-
      7    rwx

    jaguar 7% chmod 664 nontrdbse.wrl
    jaguar 8% chmod 600 nontrdhse.html
    jaguar 9% chmod 775 objects

will set the following permissions

    -rw-rw-r--    1 jbhkvwa  iupsouth        362 Mar 29 20:47 nontrdbse.wrl
    -rw----r--    1 mmccarty iupsouth        771 Mar 16 17:39 nontrdhse.html
    drwxrwxr-x    2 mmccarty ls499          4096 Mar 29 21:01 objects

Maintained by H. Edward Donley <hedonley@grove.iup.edu>
Last Modified Monday, 13-Aug-2001 16:53:27 EDT