Figure 1: Permissions
The row of numbers above each example shows the octal representation of the actual permission bits. The number in brackets at the end of the line is the octal value of the permission field. a) The typical permission bit fields 4 2 1 4 2 1 4 2 1 (777) - r w x r w x r w x ----------- ----------- ----------- owner group other b) Set User ID. If the 's' in the execute field of the file is upper case 'S', then there is no execute permission on this file. 4 4 2 1 4 - 1 4 - 1 (4755) - r w s r - x r - x ----------- SUID c) Set Group ID. See the note above. 2 4 2 1 4 - 1 4 - 1 (2755) - r w x r - s r - x ----------- SGID d) Sticky bit. This has become used to prevent users from being able to remove files they don't own in public directories such as /tmp. 1 4 2 1 4 - 1 4 - 1 (1755) d r w x r - x r - t ----------- "sticky bit"
|