On Jul 25, at 10:26 AM, Ward Oldham requested: > Maybe you could elaborate on why someone would need or want to do > something like this.
The chmod command in the command line is used to change the access permissions on a file or directory. It corresponds to changing the access privileges in the Ownership & Permissions when you're doing Get Info on a file, but there are permissions available to chmod that can't be done in the Get Info window. At its simplest there are three types of permissions that can be set read = permission to read a file or directory (folder in Macintoshish) write = permission to change or even delete a file or directory execute = permission to run a program or enter a directory There are also three groups of users user = the owner of the file (owner in Macintoshish) group = the group ownership of the file other = anybody else Any combination of the permissions can be set for any of the three user types. You can see the permissions on a file by using ls in the terminal. Here's how: First create a dummy file called test. The command "touch" creates an empty file. [Sauron:~] lee% touch test Then look at the default permissions [Sauron:~] lee% ls -l test -rw-r--r-- 1 lee staff 0 Jul 25 10:50 test The "ls -l" command tells the terminal to list files in long form, which shows a whole bunch of information. I told it to just list the file test because the rest of the files are irrelevant. The first position will have a d, if the file is a directory, which it isn't, so just - is printed. The next nine positions give the permissions in the order user group other. In this case -rw-r--r-- means rw- user has read and write permission, but not execute permission r-- group and other each only have read permission Now, we get to chmod. Suppose I type [Sauron:~] lee% chmod o+x test [Sauron:~] lee% ls -l test -rw-r--r-x 1 lee staff 0 Jul 25 10:50 test Now other has been given execute permission. Permissions can be removed just as easily: [Sauron:~] lee% chmod g-r test [Sauron:~] lee% ls -l test -rw----r-x 1 lee staff 0 Jul 25 10:50 test Group members now have no permissions. These are the infamous permissions that are being set when you "Repair Permissions" with a disk utility. The original question was about permissions of the form 777. This is a conversion of the permissions given above from the binary number way they are actually stored to base ten; i.e., --x = 001 = 1 -w- = 010 = 2 r-- = 100 = 4 To get the numerical equivalent of the permissions, you just add up the numbers for the permissions that are present; e.g., rw- = 4+2 = 6 The permissions for all three are usually written something like -rwxr-x--x = 751 So, the permissions 777 correspond to everyone having license to do anything at all to a file or directory, which usually isn't a good idea. It's usually better to think about what you actually need and restrict the permissions accordingly -- especially for a machine on the Internet. The chmod command can do a lot more. Type "man chmod" into the terminal for all the options. -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 2452 bytes Desc: not available Url : http://www.math.louisville.edu/pipermail/macgroup/attachments/20070725/8a19412e/attachment.bin
