UNIX for Dummies Questions & Answers

Hi Guys,

Aside from the following, what are other letters can be seen on permission and what do they do? Thank you.

r = read
w = write
x = execute
l = link
d = directory
s = ?

s stand for sticky bit, to stick the privileges to the subfolders

s stands for setting the User ID/Group ID.
t stands for setting the Sticky bit
The most common use of the sticky bit today is on directories, where, when set, items inside the directory can only be renamed or deleted by the item's owner, the directory's owner, or the superuser. Generally this is set on the /tmp directory to prevent ordinary users from deleting or moving other users' files.
The sticky bit can only be set by superuser root. Using the chmod command, it can be set using its octal mode 1000 or by its symbol t (s is already used by the setuid bit).
SUID stands for "Set User-ID". If the suid bit is enable on an executable, then whenever that program is run the process will take on the privilege of whoever the file owner is. For example if I have a suid binary which is owned by "root" and I execute it as my normal (non-root) user name, it will execute with all the permissions of root.


SUIDIf set, then replaces "x" in the owner permissions to "s", if owner has execute permissions, or to "S" otherwise. Examples:
-rws------ both owner execute and SUID are set
-r-S------ SUID is set, but owner execute is not setSGIDIf set, then replaces "x" in the group permissions to "s", if group has execute permissions, or to "S" otherwise. Examples:
-rwxrws--- both group execute and SGID are set
-rwxr-S--- SGID is set, but group execute is not setStickyIf set, then replaces "x" in the others permissions to "t", if others have execute permissions, or to "T" otherwise. Examples:
-rwxrwxrwt both others execute and sticky bit are set
-rwxrwxr-T sticky bit is set, but others execute is not set

Thank you guys.

Hi Slick,

Apart from the obvious read, write, execute for Owner, Group and Other permissions at the beginning of the line there are type indicators.

Code:

Type Indicator  |  Owner  |   Group  |  Other
        -           rwx        r-x       r-x

The various type indicators are as follows:

Indicator Meaning
- = Normal file
d = Directory
b = Block type special file
c = Character type special file
l = Symbolic Link
p = Named Pipe
s = Socket

welcome