I am trying to grep the third octet in IP address to an tap device on remote machine.
ssh -t user#host "/sbin/ifconfig tap0 | grep "inet" | /usr/bin/awk -F'[: ]+' '{ print $4 }' | awk -F'[.]' '{print $3}'"
I am resulting this:
inet addr:10.22.66.77 Bcast:10.22.66.255 Mask:255.255.255.0
When i run the command on the remote machine it shows 66
How to make it working with ssh -t?
Sometimes using perl is simpler:
ssh -t user#host "/sbin/ifconfig tap0" | perl -n -e 'if (/inet\saddr:\d+\.\d+\.(\d+)/) { print "$1\n"}'
it runs regular expression pattern on the local machine match on the third octet following addr: and this is then printed via $1
The pattern match is run on the local machine to avoid problems with escaping " (In your example code the " in the grep inet seems to terminate the ssh...)
This question already has answers here:
While loop stops reading after the first line in Bash
(5 answers)
Closed 1 year ago.
I need to check if telnet is happening or not on multiple remote servers.
I wrote a while loop to SSH over multiple remote servers and triggers an email whenever the telnet fails. But the issue is while loops iterates only over the first server and exits out of the script without reading remaining servers. Below is my shell script
#!bin/bash
while read host_details
do
USERNAME=$(echo $host_details | awk -F"|" '{print $1}')
HOSTIP=$(echo $host_details | awk -F"|" '{print $2}')
PORT=$(echo $host_details | awk -F"|" '{print $3}')
PROXY=$(echo $host_details | awk -F"|" '{print $4}')
PROXY_PORT=$(echo $host_details | awk -F"|" '{print $5}')
STATUS=$(ssh -n ${USERNAME}#${HOSTIP} -p${PORT} "timeout 4 bash -c \"</dev/tcp/${PROXY}/${PROXY_PORT}\"; echo $?;" < /dev/null)
if [ "$STATUS" -ne 0 ]
then
echo "Connection to $PROXY on port $PROXY_PORT failed"
mutt -s "Telnet connection to $PROXY on port $PROXY_PORT failed" abc.def#xyz.com
else
echo "Connection to $PROXY on port $PROXY_PORT succeeded"
mutt -s "Telnet connection to $PROXY on port $PROXY_PORT succeeded" abc.def#xyz.com
fi
done<.hostdetails
I observed my script works only when I remove IF condition and my while loops iterates over all the servers as expected.
Can anyone suggest why when I use IF condition the script exits after first iteration? And how to make it work and get the email alerts?
Thanks to #GordonDavisson recommendation.
The mutt in the script is treating the remaining server details as an input list, hence the script is getting terminated after reading the first server values.
Replace mutt with another email program in your script.
However, users who wish to go with mutt, then it is recommended to add content to their email body or redirect the stdin from mutt to /dev/null
Below is the working solution:
#!bin/bash
while IFS="|" read -r userName hostIp Port Proxy proxyPort
do
STATUS=$(ssh -n -tt -o LogLevel=quiet ${userName}#${hostIp} -p${Port} 'timeout 4 /bin/bash -c' \'"</dev/tcp/${Proxy}/${proxyPort}"\'; echo $? < /dev/null | tr -d '\r')
if [ "$STATUS" -ne 0 ]
then
echo "Connection to $Proxy on port $proxyPort failed" | mutt -s "${hostIp}:Telnet connection to $Proxy on port $proxyPort failed" abc.def#xyz.com
else
echo "Connection to $Proxy on port $proxyPort succeeded" | mutt -s "${hostIp}:Telnet connection to $Proxy on port $proxyPort succeeded" abc.def#xyz.com
fi
done<.hostdetails
The trim command in the solution is to delete the carriage return(\r) I was getting in the variable(STATUS)
I wanted to get the IP of my DHCP server into a bash variable.
like : IP="192.168.1.254"
I know this IP can be found in /var/lib/dhcp/dhclient.leases or in /var/log/syslog but I don't know of to extract it and put it in variable during my script (bash)
EDIT: file dhclient.leases look's like
lease {
interface "eth0";
fixed-address 192.168.1.200;
option subnet-mask 255.255.255.0;
option routers 192.168.1.254;
option dhcp-lease-time 7200;
option dhcp-message-type 5;
option domain-name-servers 192.168.1.254;
option dhcp-server-identifier 192.168.1.254;
option host-name "bertin-Latitude-E6430s";
option domain-name "laboelec";
renew 1 2015/02/16 10:54:34;
rebind 1 2015/02/16 11:53:49;
expire 1 2015/02/16 12:08:49;
}
I want the IP from line option dhcp-server-identifier 192.168.1.254;.
To more compatibility I finally opted for a simple solution which is to send the IP server like a string on broadcast every seconds. For that I use socat (because netcat can't send message to braodcast)
my DHCP server run this script in background:
#!/bin/bash
interface="eth0"
IP=$(ifconfig $interface | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}')
Broadcast=$(ifconfig $interface | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f3 | awk '{ print $1}')
Port="5001"
while [ true ];
do
sleep 1
echo $IP | socat - UDP4-DATAGRAM:$Broadcast:$Port,so-broadcast
#to listen: netcat -l -u $Broadcast -p $Port
done
exit 0
There are several terminals in a single localhost in which I have ssh-ed into the same user and same IP address. I want to find all the terminals in which a remote host has been logged, terminate all processes running in those and log out of that remote host. I succeeded using the following shell script.
#Find list of terminals in which the remote host is logged in.
openedTerminals=`ssh $user#$publicIP "ps -aux | grep -i $user#pts | grep -v grep | cut -d' ' -f 3"`
#close all the ssh sessions to that remote host
i=1
terminalPID=`echo $openedTerminals | cut -d' ' -f $i`
while [[ -n "$terminalPID" ]]
do
ssh $user#$publicIP "kill $terminalPID"
i=`expr $i + 1`
terminalPID=`echo $openedTerminals | cut -d' ' -f $i`
done
I used the following command to open a new terminal and ssh into a remote host which worked fine when executed from the command prompt:
gnome-terminal -window-with-profile=NOCLOSEPROFILE -e "ssh -X $user#$publicIP"
Apart from doing the work of the 1st code, I want to open a new terminal (by ssh-ing into another remote machine) for every remote machine which was terminated by the 1st code. So I tried to insert the above command in the 1st code as:
#Find list of terminals in which the remote host is logged in.
openedTerminals=`ssh $user#$publicIP "ps -aux | grep -i $user#pts | grep -v grep | cut -d' ' -f 3"`
#close all the ssh sessions to that remote host
i=1
terminalPID=`echo $openedTerminals | cut -d' ' -f $i`
while [[ -n "$terminalPID" ]]
do
ssh $user#$publicIP "kill $terminalPID"
gnome-terminal -window-with-profile=NOCLOSEPROFILE -e "ssh -X $newUser#$newPublicIP"
i=`expr $i + 1`
terminalPID=`echo $openedTerminals | cut -d' ' -f $i`
done
But this starts running in an infinite loop and opens infinite number of new terminals.
Please tell me where I am wrong and suggest a way to correct it in order to get the desired solution.
Also, I wish to add a command in the same shell script (1st code) to close the terminals in which the remote machine was logged out. Can anyone please guide me on this?
Thanks in advance,
Saeya
When only one terminal which is ssh-ed to the remote machine is opened, this runs in an infinite loop because of the "cut" command. If there is a separate case to handle one terminal this will work fine.
How can I write a Linux Bash script that tells me which computers are ON in my LAN?
It would help if I could give it a range of IP addresses as input.
I would suggest using nmap's ping-scan flag,
$ nmap -sn 192.168.1.60-70
Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2009-04-09 20:13 BST
Host machine1.home (192.168.1.64) appears to be up.
Host machine2.home (192.168.1.65) appears to be up.
Nmap finished: 11 IP addresses (2 hosts up) scanned in 0.235 seconds
That said, if you want to write it yourself (which is fair enough), this is how I would do it:
for ip in 192.168.1.{1..10}; do ping -c 1 -t 1 $ip > /dev/null && echo "${ip} is up"; done
..and an explanation of each bit of the above command:
Generating list of IP addresses
You can use the {1..10} syntax to generate a list of numbers, for example..
$ echo {1..10}
1 2 3 4 5 6 7 8 9 10
(it's also useful for things like mkdir {dir1,dir2}/{sub1,sub2} - which makes dir1 and dir2, each containing sub1 and sub2)
So, to generate a list of IP's, we'd do something like
$ echo 192.168.1.{1..10}
192.168.1.1 192.168.1.2 [...] 192.168.1.10
Loops
To loop over something in bash, you use for:
$ for thingy in 1 2 3; do echo $thingy; done
1
2
3
Pinging
Next, to ping.. The ping command varies a bit with different operating-systems, different distributions/versions (I'm using OS X currently)
By default (again, on the OS X version of ping) it will ping until interrupted, which isn't going to work for this, so ping -c 1 will only try sending one packet, which should be enough to determine if a machine is up.
Another problem is the timeout value, which seems to be 11 seconds on this version of ping.. It's changed using the -t flag. One second should be enough to see if a machine on the local network is alive or not.
So, the ping command we'll use is..
$ ping -c 1 -t 1 192.168.1.1
PING 192.168.1.1 (192.168.1.1): 56 data bytes
--- 192.168.1.1 ping statistics ---
1 packets transmitted, 0 packets received, 100% packet loss
Checking ping result
Next, we need to know if the machine replied or not..
We can use the && operator to run a command if the first succeeds, for example:
$ echo && echo "It works"
It works
$ nonexistantcommand && echo "This should not echo"
-bash: nonexistantcommand: command not found
Good, so we can do..
ping -c 1 -t 1 192.168.1.1 && echo "192.168.1.1 is up!"
The other way would be to use the exit code from ping.. The ping command will exit with exit-code 0 (success) if it worked, and a non-zero code if it failed. In bash you get the last commands exit code with the variable $?
So, to check if the command worked, we'd do..
ping -c 1 -t 1 192.168.1.1;
if [ $? -eq 0 ]; then
echo "192.168.1.1 is up";
else
echo "ip is down";
fi
Hiding ping output
Last thing, we don't need to see the ping output, so we can redirect stdout to /dev/null with the > redirection, for example:
$ ping -c 1 -t 1 192.168.1.1 > /dev/null && echo "IP is up"
IP is up
And to redirect stderr (to discard the ping: sendto: Host is down messages), you use 2> - for example:
$ errorcausingcommand
-bash: errorcausingcommand: command not found
$ errorcausingcommand 2> /dev/null
$
The script
So, to combine all that..
for ip in 192.168.1.{1..10}; do # for loop and the {} operator
ping -c 1 -t 1 192.168.1.1 > /dev/null 2> /dev/null # ping and discard output
if [ $? -eq 0 ]; then # check the exit code
echo "${ip} is up" # display the output
# you could send this to a log file by using the >>pinglog.txt redirect
else
echo "${ip} is down"
fi
done
Or, using the && method, in a one-liner:
for ip in 192.168.1.{1..10}; do ping -c 1 -t 1 $ip > /dev/null && echo "${ip} is up"; done
Problem
It's slow.. Each ping command takes about 1 second (since we set the -t timeout flag to 1 second). It can only run one ping command at a time.. The obvious way around this is to use threads, so you can run concurrent commands, but that's beyond what you should use bash for..
"Python threads - a first example" explains how to use the Python threading module to write a multi-threaded ping'er.. Although at that point, I would once again suggest using nmap -sn..
In the real world, you could use nmap to get what you want.
nmap -sn 10.1.1.1-255
This will ping all the addresses in the range 10.1.1.1 to 10.1.1.255 and let you know which ones answer.
Of course, if you in fact want to do this as a bash exercise, you could run ping for each address and parse the output, but that's a whole other story.
Assuming my network is 10.10.0.0/24, if i run a ping on the broadcast address like
ping -b 10.10.0.255
I'll get an answer from all computers on this network that did not block their ICMP ping port.
64 bytes from 10.10.0.6: icmp_seq=1 ttl=64 time=0.000 ms
64 bytes from 10.10.0.12: icmp_seq=1 ttl=64 time=0.000 ms
64 bytes from 10.10.0.71: icmp_seq=1 ttl=255 time=0.000 ms
So you just have to extract the 4th column, with awk for example:
ping -b 10.10.0.255 | grep 'bytes from' | awk '{ print $4 }'
10.10.0.12:
10.10.0.6:
10.10.0.71:
10.10.0.95:
Well, you will get duplicate, and you may need to remove the ':'.
EDIT from comments :
the -c option limits the number of pings
since the script will end, we can also limit ourself on unique IPs
ping -c 5 -b 10.10.0.255 | grep 'bytes from' | awk '{ print $4 }' | sort | uniq
There is also fping:
fping -g 192.168.1.0/24
or:
fping -g 192.168.1.0 192.168.1.255
or show only hosts that are alive:
fping -ag 192.168.1.0/24
It pings hosts in parallel so the scan is very fast. I don't know a distribution which includes fping in its default installation but in most distributions you can get it through the package manager.
Also using the "ping the broadcast address" method pointed out by chburd, this pipe should do the trick for you:
ping -c 5 -b 10.11.255.255 | sed -n 's/.* \([0-9]\+\.[0-9]\+\.[0-9]\+\.[0-9]\+\).*/\1/p' | sort | uniq
Of course, you'd have to change the broadcast address to that of your network.
Just for fun, here's an alternate
#!/bin/bash
nmap -sP 192.168.1.0/24 > /dev/null 2>&1 && arp -an | grep -v incomplete | awk '{print$2}' | sed -e s,\(,, | sed -e s,\),,
If you're limiting yourself to only having the last octet changing, this script should do it. It should be fairly obvious how to extend it from one to multiple octets.
#! /bin/bash
BASE=$1
START=$2
END=$3
counter=$START
while [ $counter -le $END ]
do
ip=$BASE.$counter
if ping -qc 2 $ip
then
echo "$ip responds"
fi
counter=$(( $counter + 1 ))
done
ip neighbor
arp -a
Arpwatch
As other posters pointed out, nmap is the way to go, but here's how to do the equivalent of a ping scan in bash. I wouldn't use the broadcast ping, as a lot of systems are configured not to respond to broadcast ICMP nowadays.
for i in $(seq 1 254); do
host="192.168.100.$i"
ping -c 1 -W 1 $host &> /dev/null
echo -n "Host $host is "
test $? -eq 0 && echo "up" || echo "down"
done
#!/bin/bash
#Get the ip address for the range
ip=$(/sbin/ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}' | cut -d"." -f1,2,3)
# ping test and list the hosts and echo the info
for range in $ip ; do [ $? -eq 0 ] && ping -c 1 -w 1 $range > /dev/null 2> /dev/null && echo "Node $range is up"
done
Although an old question, it still seems to be important (at least important enough for me to deal with this). My script relies on nmap too, so nothing special here except that ou can define which interface you want to scan and the IP Range is created automagically (at least kind of).
This is what I came up with
#!/bin/bash
#Script for scanning the (local) network for other computers
command -v nmap >/dev/null 2>&1 || { echo "I require nmap but it's not installed. Aborting." >&2; exit 1; }
if [ -n ""$#"" ]; then
ip=$(/sbin/ifconfig $1 | grep 'inet ' | awk '{ print $2}' | cut -d"." -f1,2,3 )
nmap -sP $ip.1-255
else
echo -e "\nThis is a script for scanning the (local) network for other computers.\n"
echo "Enter Interface as parameter like this:"
echo -e "\t./scannetwork.sh $(ifconfig -lu | awk '{print $2}')\n"
echo "Possible interfaces which are up are: "
for i in $(ifconfig -lu)
do
echo -e "\033[32m \t $i \033[39;49m"
done
echo "Interfaces which could be used but are down at the moment: "
for i in $(ifconfig -ld)
do
echo -e "\033[31m \t $i \033[39;49m"
done
echo
fi
One remark: This script is created on OSX, so there might be some changes to linux environments.
If you want to provide a list of hosts it can be done with nmap, grep and awk.
Install nmap:
$ sudo apt-get install nmap
Create file hostcheck.sh like this:
hostcheck.sh
#!/bin/bash
nmap -sP -iL hostlist -oG pingscan > /dev/null
grep Up pingscan | awk '{print $2}' > uplist
grep Down pingscan | awk '{print $2}' > downlist
-sP: Ping Scan - go no further than determining if host is online
-iL : Input from list of hosts/networks
-oG : Output scan results in Grepable format, to the given filename.
/dev/null : Discards output
Change the access permission:
$ chmod 775 hostcheck.sh
Create file hostlist with the list of hosts to be checked (hostname or IP):
hostlist (Example)
192.168.1.1-5
192.168.1.101
192.168.1.123
192.168.1.1-5 is a range of IPs
Run the script:
./hostcheck.sh hostfile
Will be generated files pingscan with all the information, uplist with the hosts online (Up) and downlist with the hosts offline (Down).
uplist (Example)
192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
192.168.1.101
downlist (Example)
192.168.1.5
192.168.1.123
Some machines don't answer pings (e.g. firewalls).
If you only want the local network you can use this command:
(for n in $(seq 1 254);do sudo arping -c1 10.0.0.$n & done ; wait) | grep reply | grep --color -E '([0-9]+\.){3}[0-9]+'
Explanations part !
arping is a command that sends ARP requests. It is present on most of linux.
Example:
sudo arping -c1 10.0.0.14
the sudo is not necessary if you are root ofc.
10.0.0.14 : the ip you want to test
-c1 : send only one request.
&: the 'I-don't-want-to-wait' character
This is a really useful character that give you the possibility to launch a command in a sub-process without waiting him to finish (like a thread)
the for loop is here to arping all 255 ip addresses. It uses the seq command to list all numbers.
wait: after we launched our requests we want to see if there are some replies. To do so we just put wait after the loop.
wait looks like the function join() in other languages.
(): parenthesis are here to interpret all outputs as text so we can give it to grep
grep: we only want to see replies. the second grep is just here to highlight IPs.
hth
Edit 20150417: Maxi Update !
The bad part of my solution is that it print all results at the end. It is because grep have a big enough buffer to put some lines inside.
the solution is to add --line-buffered to the first grep.
like so:
(for n in $(seq 1 254);do sudo arping -c1 10.0.0.$n & done ; wait) | grep --line-buffered reply | grep --color -E '([0-9]+\.){3}[0-9]+'
#!/bin/bash
for ((n=0 ; n < 30 ; n+=1))
do
ip=10.1.1.$n
if ping -c 1 -w 1 $ip > /dev/null 2> /dev/null >> /etc/logping.txt; then
echo "${ip} is up" # output up
# sintax >> /etc/logping.txt log with .txt format
else
echo "${ip} is down" # output down
fi
done
The following (evil) code runs more than TWICE as fast as the nmap method
for i in {1..254} ;do (ping 192.168.1.$i -c 1 -w 5 >/dev/null && echo "192.168.1.$i" &) ;done
takes around 10 seconds, where the standard nmap
nmap -sP 192.168.1.1-254
takes 25 seconds...
Well, this is part of a script of mine.
ship.sh 🚢 A simple, handy network addressing 🔎 multitool with plenty of features 🌊
Pings network, displays online hosts on that network with their local IP and MAC address
It doesn't require any edit. Needs root permission to run.
GOOGLE_DNS="8.8.8.8"
ONLINE_INTERFACE=$(ip route get "${GOOGLE_DNS}" | awk -F 'dev ' 'NR == 1 {split($2, a, " "); print a[1]}')
NETWORK_IP=$(ip route | awk "/${ONLINE_INTERFACE}/ && /src/ {print \$1}" | cut --fields=1 --delimiter="/")
NETWORK_IP_CIDR=$(ip route | awk "/${ONLINE_INTERFACE}/ && /src/ {print \$1}")
FILTERED_IP=$(echo "${NETWORK_IP}" | awk 'BEGIN{FS=OFS="."} NF--')
ip -statistics neighbour flush all &>/dev/null
echo -ne "Pinging ${NETWORK_IP_CIDR}, please wait ..."
for HOST in {1..254}; do
ping "${FILTERED_IP}.${HOST}" -c 1 -w 10 &>/dev/null &
done
for JOB in $(jobs -p); do wait "${JOB}"; done
ip neighbour | \
awk 'tolower($0) ~ /reachable|stale|delay|probe/{printf ("%5s\t%s\n", $1, $5)}' | \
sort --version-sort --unique