File Permissions

One of the most common reasons why things don't work right in UNIX is file permissions!
Every file you create has your name attached to it
Examine file permissions with the ls -l command

d rwx r-x --x

^ ^^^ ^^^ ^^^

1..2...3...4

4 = Others have permission only to execute

3 = Group has permission only to read and execute

2 = User (file owner) has permission to read, write and execute

1 = For directories, read allows permission to list files, write can create or delete, execute allow to use the cd command

Return to Main Menu | File Organization Menu | Change Permissions | DOWN

Changing Permissions

chmod [ugo] filename

Changes the user (u), group (g) or other (o) file permission to read (r), write (w), or execute (x) the file. This procedure is done by indicating which group (u, g, or o) then use a plus sign to add a permission or a minus sign to take away a permission.

An octal system can also be used: 1 is execute, 2 is write, and 4 is read. Combinations are obtained as sums.

Examples:

chmod 777 <filename>

Result:

gives everyone permission to do everything (highly not recommendable)

chmod 765 <filename>

Result:

user permission to everything and group has read and write permission only and others has read and execute permission

chmod 741 <filename>

Result:

user permission to everything and group has read permission only and other has execute permission only

chmod u+rwx,g-rwx,o-rwx <filename>

Result:

user is the only one with permission and can read, write , and execute

Return to Main Menu | File Organization Menu | Permissions | UP