Sharing internet [Macbook and PS3]

I wanted to connect to internet from my PS3 to play online game but I am using a wimax internet modem so its not possible to directly connect it to PS3 because PS3 will not recognize it as a wimax modem.
I have a macbook pro and i wanted to use it's airport to share wimax internet to PS3.
this is how I did it:

step 0: open system preferences->network->airport turn it on then select "create network" from network name section drop-down, if you do not have a network. If so create a network and named it same as your macbook name.
step 1: open system preferences and click to sharing
step 2: enable internet sharing
in share your connection from section select your internet connection
and in to computers using section select Airport
step 3: click on Airport Options... button to set wifi password (optional)
step 4: open terminal
step 5: run this command $ cp /etc/bootpd.plist ~/Documents
step 6: open bootpd.plist file from your Document folder and edit using any text editor
you will find these two lines at the end of the file,
[key]reply_threshold_seconds[/key]
[integer]4[/integer]
change it to this
[key]reply_threshold_seconds[/key]
[integer]0[/integer]
(note: when you read pretend [ as < and ] as > )

step 7: copy modified file to /etc using this command, $ sudo cp ~/Documents/bootpd.plist /etc
step 8: start internet sharing

power up your ps3 and scan for wireless network and connect :)

php - keyboard input

I was thinking yesterday that is it possible in PHP to take input from keyboard. I started to digg and find out it is possible but no one use it because PHP was not designed to take input from keyboard :) anyway i am posting code here take a look :

#!/usr/bin/php
[php open tag]
function getinput(){
print("Your input: ");
$stdin = fopen("php://stdin", 'r');
$input = fgets($stdin, 1024);
$input = trim($input);
fclose($stdin);
return $input;
}

function output($message){
print $message."\n";
}

$message = getinput();
output($message);
[php end tag]

What are the SUID, SGID and the Sticky Bits?

link: Original Post

* SUID or setuid: change user ID on execution. If setuid bit is set, when the file will be executed by a user, the process will have the same rights as the owner of the file being executed.
* SGID or setgid: change group ID on execution. Same as above, but inherits rights of the group of the owner of the file on execution. For directories it also may mean that when a new file is created in the directory it will inherit the group of the directory (and not of the user who created the file).
* Sticky bit: It was used to trigger process to "stick" in memory after it is finished, now this usage is obsolete. Currently its use is system dependent and it is mostly used to suppress deletion of the files that belong to other users in the folder where you have "write" access to.

Numeric representation

Octal digit Binary value Meaning
0 000 setuid, setgid, sticky bits are cleared
1 001 sticky bit is set
2 010 setgid bit is set
3 011 setgid and sticky bits are set
4 100 setuid bit is set
5 101 setuid and sticky bits are set
6 110 setuid and setgid bits are set
7 111 setuid, setgid, sticky bits are set

Textual representation

SUID, If 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 set

SGID, If 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 set

Sticky, If 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

Setting the sticky bit on a directory : chmod +t

If you have a look at the /tmp permissions, in most GNU/Linux distributions, you'll see the following:

lokams@tempsrv# ls -l | grep tmp
drwxrwxrwt 10 root root 4096 2006-03-10 12:40 tmp

The "t" in the end of the permissions is called the "sticky bit". It replaces the "x" and indicates that in this directory, files can only be deleted by their owners, the owner of the directory or the root superuser. This way, it is not enough for a user to have write permission on /tmp, he also needs to be the owner of the file to be able to delete it.

In order to set or to remove the sticky bit, use the following commands:

# chmod +t tmp
# chmod -t tmp

Setting the SGID attribute on a directory : chmod g+s

If the SGID (Set Group Identification) attribute is set on a directory, files created in that directory inherit its group ownership. If the SGID is not set the file's group ownership corresponds to the user's default group.

In order to set the SGID on a directory or to remove it, use the following commands:

# chmod g+s directory
# chmod g-s directory

When set, the SGID attribute is represented by the letter "s" which replaces the "x" in the group permissions:

# ls -l directory
drwxrwsr-x 10 george administrators 4096 2006-03-10 12:50 directory

Setting SUID and SGID attributes on executable files : chmod u+s, chmod g+s

By default, when a user executes a file, the process which results in this execution has the same permissions as those of the user. In fact, the process inherits his default group and user identification.

If you set the SUID attribute on an executable file, the process resulting in its execution doesn't use the user's identification but the user identification of the file owner.

For instance, consider the script myscript.sh which tries to write things into mylog.log :

# ls -l
-rwxrwxrwx 10 george administrators 4096 2006-03-10 12:50 myscript.sh
-rwxrwx--- 10 george administrators 4096 2006-03-10 12:50 mylog.log

As you can see in this example, George gave full permissions to everybody on myscript.sh but he forgot to do so on mylog.log. When Robert executes myscript.sh, the process runs using Robert's user identification and Robert's default group (robert:senioradmin). As a consequence, myscript fails and reports that it can't write in mylog.log.

In order to fix this problem George could simply give full permissions to everybody on mylog.log. But this would make it possible for anybody to write in mylog.log, and George only wants this file to be updated by his myscript.sh program. For this he sets the SUID bit on myscript.sh:

# chmod u+s myscript.sh

As a consequence, when a user executes the script the resulting process uses George's user identification rather than the user's. If set on an executable file, the SUID makes the process inherit the owner's user identification rather than the one of the user who executed it. This fixes the problem, and even though nobody but George can write directly in mylog.log, anybody can execute myscript.sh which updates the file content.

Similarly, it is possible to set the SGID attribute on an executable file. This makes the process use the owner's default group instead of the user's one. This is done by:

# chmod g+s myscript.sh

By setting SUID and SGID attributes the owner makes it possible for other users to execute the file as if they were him or members of his default group.

The SUID and GUID are represented by a "s" which replaces the "x" character respectively in the user and group permissions:

# chmod u+s myscript.sh
# ls -l
-rwsrwxrwx 10 george administrators 4096 2006-03-10 12:50 myscript.sh
# chmod u-s myscript.sh
# chmod g+s myscript.sh
# ls -l
-rwxrwsrwx 10 george administrators 4096 2006-03-10 12:50 myscript.sh