works on Linux and Solaris. I think it will work on nearly all *nix-es Show Sample Output
This is useful if you have need to do port forwarding and your router doesn't assign static IPs, you can add it to a script in a cron job that checks if you IP as recently changed or with a trigger script. This was tested on Mac OSX.
PING parameters c 1 limits to 1 pinging attempt q makes the command quiet (or silent mode) /dev/null 2>&1 is to remove the display && echo ONLINE is executed if previous command is successful (return value 0) || echo OFFLINE is executed otherwise (return value of 1 if unreachable or 2 if you're offline yourself). I personally use this command as an alias with a predefined machine name but there are at least 2 improvements that may be done. Asking for the machine name or IP Escaping the output so that it displays ONLINE in green and OFFLINE in red (for instance).
The +short option should make dig less chatty.
Intended for dynamic ip OpenDNS users, this command will update your OpenDNS network IP. For getting your IP, you can use one of the many one-liners here on commandlinefu. Example: I use this in a script which is run by kppp after it has successfully connected to my ISP: --- #!/bin/bash IP="`curl -s http://checkip.dyndns.org/ | grep -o '[[:digit:].]\+'`" PW="hex-obfuscated-pw-here" if [ "$IP" == "" ] ; then echo 'Not online.' ; exit 1 else wget -q --user=topsecret --password="`echo $PW | xxd -ps -r`" 'https://updates.opendns.com/nic/update?hostname=myhostname&myip='"$IP" -O - /etc/init.d/ntp-client restart & fi --- PS: DynDNS should use a similar method, if you know the URL, please post a comment. (Something with members.dyndns.org, if I recall correctly) Show Sample Output
Interfaces like lo can be omitted from the beginning, there are probably better ways of doing this, i'm a noob at awk. Show Sample Output
The curl command retrieve the HTML text containing the IP address. The grep command picks out the IP address from that HTML text. Show Sample Output
There's been so many ways submitted to get your external IP address that I decided we all need a command that will just go pick a random one from the list and run it. This gets a list of "Get your external IP" commands from commanlinefu.com and selects a random one to run. It will run the command and print out which command it used.
This is not a serious entry, but it was a learning exercise for me writing it. My personal favourite is "curl icanhazip.com". I really don't think we need any other ways to do this, but if more come you can make use of them with this command ;o).
Here's a more useful command that always gets the top voted "External IP" command, but it's not so much fun:
eval $(curl -s http://www.commandlinefu.com/commands/matching/external/ZXh0ZXJuYWw=/sort-by-votes/plaintext|sed -n '/^# Get your external IP address$/{n;p;q}')
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I'm just a simple programmer. I find dig too verbose. host tells me alias(es) and IP address in a quick to grok format with nothing special to remember for input parameters. With thanks to http://www.cyberciti.biz/faq/how-to-test-or-check-reverse-dns/ Show Sample Output
has the benefit of being a bit more cross-platform.
gives u each configured IP in a seperate line. Show Sample Output
ip address show | grep eth0 | sed '1d' | awk '{print $2}'
does the same, but shows network-prefix.
Converts IP octets to hex using printf command. Useful for generating pxeboot aliases in the pxelinux.cfg folder. Show Sample Output
Instead of hard-coding in a check to scrape info from ifconfig based on a specific interface, do it in a more portable way. This works really well if you switch between wired, wireless, bluetooth or even VPN connections. You can get your current IP in a script (since it'll be something like tun0 instead of eth0 or wlan1). This uses a well known public ip address 8.8.8.8, but it doesn't actually connect to it, it just shows you the route it would take. Show Sample Output
To show ipv6 instead, use [[ -6 ]] instead of [[ -4 ]]
ip -o -6 a s | awk -F'[ /]+' '$2!~/lo/{print $4}'
To show only the IP of a specific interface, in case you get more than one result:
ip -o -4 a s eth0 | awk -F'[ /]+' '$2!~/lo/{print $4}'
ip -o -4 a s wlan0 | awk -F'[ /]+' '$2!~/lo/{print $4}'
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I have used single packet, and in a silent mode with no display of ping stats. This is with color and UI improvement to the http://www.commandlinefu.com/commands/view/10220/check-if-a-machine-is-online. It is as per the enhancements suggested. Show Sample Output
Why use many different utilities all piped together, when you only need two? Show Sample Output
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