How to get wireless interface?

[hakermania]

ifconfig displays a lot of information, but im making a program and I was possible to take the current interface through the command

airmon-ng and some string editing.

Unfortunately the above command is very slow, it does approximately 2 seconds to execute and my program hangs.

Is there any secure way to take the current interface through ifconfig?
Or is the interface written somewhere specifically like the hostname does? (/etc/hostname)

Please mention that my program requires root permissions to run, so there is no problem with executing command requiring su permissions.

Thanks in advance for any replies!

[hakermania]

Well, I found my own way, but I cannot be sure that it will always work...


ifconfig > tmp;
a=0;
while read line; do
a=$(expr $a + 1);
if [ $a -eq 18 ]; then
b=${line%% *};
fi;
done < tmp
rm tmp
echo "'$b'"This will output 'wlan0' in my case but I cannot be sure that always and in every PC the interface is being outputed in the 18th line of $(ifconfig)!!!
But if it does, then please post here that this works for you too...

[dwhitney67]

See if the contents of /proc/net/wireless can be used. On my two dissimilar Ubuntu systems, the third line contains the information you require.


Inter-| sta-| Quality | Discarded packets | Missed | WE
face | tus | link level noise | nwid crypt frag retry misc | beacon | 22
eth1: 0000 5. -54. -57. 0 159 0 2309 0 0

Check you system to see if in lieu of eth1, you have wlan0.

P.S. I just checked an RHEL virtual machine that does not have a wireless interface. There was no third line in the output.

[hakermania]

the /proc/net/wireless file doesn't include the wlan0 string in my case :/
I let the pc searching for files containing the word wlan0 and nothing interesting was found :/

[hakermania]

What about the /proc/net/dev file? My interface appears on the 3rd line.....What about yours people out there?

the /prov/net/arp says it clear, but i'm still not sure....

[slavik]

iwconfig 2>&1 | grep IEEE | awk '{print $1}'

[hakermania]

iwconfig 2>&1 | grep IEEE | awk '{print $1}'
I wasn't aware of the command 'iwconfig'.
How do you guarantee that this is going to work at everybody running ubuntu-like OS and being in a laptop?

[slavik]

slavik@home-main:~$ dpkg -S iwconfig
wireless-tools: /usr/share/man/cs/man8/iwconfig.8.gz
wireless-tools: /usr/share/man/fr.UTF-8/man8/iwconfig.8.gz
wireless-tools: /usr/share/man/man8/iwconfig.8.gz
wireless-tools: /usr/share/man/fr.ISO8859-1/man8/iwconfig.8.gz
wireless-tools: /sbin/iwconfig
slavik@home-main:~$ apt-cache showpkg wireless-tools
Package: wireless-tools
Versions:
30~pre9-3ubuntu6 (/var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_natty_main_bina ry-amd64_Packages) (/var/lib/dpkg/status)
Description Language:
File: /var/lib/apt/lists/us.archive.ubuntu.com_ubuntu_dists_natty_main_bina ry-amd64_Packages
MD5: 34c7dc532552aa22b7a3e5860d0000e7


Reverse Depends:
kubuntu-desktop,wireless-tools
broadcom-sta-source,wireless-tools
broadcom-sta-common,wireless-tools
atmel-firmware,wireless-tools
xubuntu-desktop,wireless-tools
wifi-radar,wireless-tools
wicd-daemon,wireless-tools
whereami,wireless-tools
ubuntustudio-desktop,wireless-tools
ubuntu-sugar-remix,wireless-tools
ubuntu-chinese-desktop,wireless-tools
network-config,wireless-tools
lubuntu-desktop,wireless-tools
laptop-mode-tools,wireless-tools
kismet,wireless-tools
brdesktop-common,wireless-tools
aircrack-ng,wireless-tools
ubuntu-desktop,wireless-tools
pm-utils,wireless-tools
pcmciautils,wireless-tools
linux-wlan-ng,wireless-tools
kubuntu-desktop,wireless-tools
acpi-support,wireless-tools
Dependencies:
30~pre9-3ubuntu6 - libc6 (2 2.7) libiw30 (2 30~pre1)
Provides:
30~pre9-3ubuntu6 -
Reverse Provides:
slavik@home-main:~$


Unless you remove (or modify) one of the -desktop packages (depends on the version of ubuntu you are using), dpkg is supposed to guarantee that it _WILL_ be there and available.

[hakermania]

I don't say that the iwconfig command won't be available but is can I take for granted that it will show the default interface on every pc?

[slavik]

there is no such thing as "the default interface"

[hakermania]

What I need is the most secure way to get the wireless interface that the system uses to connect to the internet.
You proposed a solution that it works for me, but that's not the point. I myself have already found more than 9 ways to take this interface, but none of them is secure, because they didn't work in all situations. So, what I search for is the most secure way. So, I'm asking how do you know that your solution is the most secure way. I think you got me now..

Thx again :)

[slavik]

you are basing this solution on an assumption, which is _STUPID_ ... but!



DEFAULT_IFACE=$(netstat -rn | grep '^0\.0\.0\.0' | awk '{print $8}')
if [[ ${DEFAULT_IFACE} == $(iwconfig 2>&1 | grep IEEE | grep ${DEFAULT_IFACE} | awk '{print $1}' ) ]]; then
echo ${DEFAULT_IFACE} "appears to be the default wireless interface used for all routing if there is nothing stricter defined."
fi


Did I mention, this solution is stupid? Take a guess why. (Hint: It has to do with what the internet really is, but you have to really understand that.)

[hakermania]

:roll::roll::roll::roll:


Well, I don't know what to reply because I didn't get what the assumption is (I trust ubuntuforums for their solutions and you, as you are from the staff)....

And the code you posted above I am not sure it will work (because I've already tested it in several PCs and not all have an IP there, at the output of netstat -rn)

[slavik]

the internet is a giant network of computers. when you have 3 interfaces on it, they can be used to route to different subnets. if you connect to a network via VPN, you can get a ton more routes (where I work, there are like 20 subnets added), adding in that you might want end up using dns server inside the vpn, all of your traffic might end up going through there.

what do those PCs show when you run netstat -rn? can you also show output of iwconfig for those?

EDIT: You do realize that the code I posted so far was meant to give you ideas, right?