Hello. How can i check who is connected to my wifi. I know there is way with router site but is there another way with terminal or any program ? Thank you

Luke

there is many ways  

1 ) most obvious  login to you router and check the dhcp listsings
2 ) use wireshark
3 ) nmap
4 ) ettercap

the list goes on

you use ettercap and arp the network use h and then l to lists hosts
if there is have some fun with them using etterfilters and metasploit

heres something I threw together for a simple hosts scan

** Note this is not a stealth scan nor IDS avoidance its for your home network you can adjust the nmap phrams to suit your required needs

hostscan () {
## hostscan snippet for www.blackbuntu.com // r083rt
Ip=$(ifconfig | grep 'inet addr' | cut -d':' -f2 | awk '{print $1}' | grep -Ev 127.0.0.1)
Nmap=$(ip route show default | awk '/default/ {print $3 "/"24}')
Gateway=$(ip route show default | awk '/default/ {print $3 }')
echo "" ;sudo nmap -O $Nmap --exclude "$Ip","$Gateway"  | grep -e 'Nmap scan report for' | grep -Ev 'Nmap scan report for [0-9]' | awk '{print "\033[1;32m UserID\033[0m " $5  "\033[1;31m IP\033[0m" , $6 }' | grep -Ev 'UserID [0-9]' | sed 's/[)(]//g';echo
}
copy and paste his into your bashrc

open a terminal and run : hostscan

this is a quick dirty example of what you can do

If you want me to increase stealth and mod it i.e improve it let me know Ill add and edit nmap switches to grab more info etc etc and create a host of scans

very simple let very boring  

as I SAID there is many ways your option is another way

I just gave him a host of options  

a better option would be using arpscan !!!! there is a lot more switches to play with

sudo apt-get -y install arp-scan
sudo arp-scan -l


Im not posting this for One-upmanship

Weveg I have a lot of respect you and what you do on the forum

Im posting a host of options for the user to help him learn

posting "arp -a"  is not exactly giving a lot of info regarding 'what other ways' as he did ask what other ways is there

we are here to help the users to learn and give as much info to help them move along so they can help the ones under them
is'nt that the way it works i.e linux community

while no one is about spoon feeding it is important to help the beginner to a stage where he or she can start to navigate and
do things on there own and hen they can take over and help others

Yes nmap does have that option I did it a different waY to pipe and remove the gateway and IP while this can be done through map
I decided to it my way !!!! like it or hate it... it works

FGS you can't win for losing on this forum

i don't know this tool, but have you read the man page? even --help? your request is off topic, and you should open another 3d, you have to know how arp is.
Reading the error that you have posted, eth0 have not an IP address 'cause your are connected with wlan0, reading the first line of the man page [ 0 ], you must specify the interface otherwise "The network interface to use can be specified with the --interface option. If this option is not present, arp-scan will search the system interface list for the lowest numbered, configured up interface (excluding loopback).By default, the ARP packets are sent to the Ethernet broadcast address, ff:ff:ff:ff:ff:ff, but that can be changed with the --destaddr option. ". Luke, we know that you are new on linux world, so keep in mind which man page, --help, and google are the most important resources that you have to use!


[ 0 ] http://linux.die.net/man/1/arp-scan

Ok, i understand your trouble, but you can learn step by step english, or you can translate with google, or you can googling and found someone from your country that have used arp-scan and explained how to use it, or you can found man page in your own language... there are a lot of possibility, only "wish" !!