commandlinefu.com is the place to record those command-line gems that you return to again and again.
Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.
If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/
You can sign-in using OpenID credentials, or register a traditional username and password.
First-time OpenID users will be automatically assigned a username which can be changed after signing in.
Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.
Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):
Subscribe to the feed for:
Open Port Check
See connection's tcp timers
Count on a specific port (80) - FreeBSD friendly.
This obtains a list of open connections that a user is connected to if he/she is using a SSH tunnel
cut -f1,2 - IP range 16
cut -f1,2,3 - IP range 24
cut -f1,2,3,4 - IP range 24
Show state of NAT, readed from '/proc/net/ip_conntrack' or '/proc/net/nf_conntrack'
See who is using a specific port. Especially when you're using AIX. In Ubuntu, for example, this can easily be seen with the netstat command.
This is also perl-less, and only uses AWK as its postprocessor. Tested with GAWK and MAWK.
if you don't do --numeric-ports, netstat will try to resolve them to names
Easy to remenber. Fot TCP only use: netstat -plant
Lists all opened sockets (not only listeners), no DNS resolution (so it's fast), the process id and the user holding the socket.
Previous samples were limiting to TCP too, this also lists UDP listeners.
Check open TCP and UDP ports
While `lsof` will work, why not use the tool designed explicitly for this job?
(If not run as root, you will only see the names of PID you own)
shell loop to scan netstat output avoiding loolback aliases (local/remote swap for local connections)
We use the "convert" command (ImageMagick package) : see man convert (http://www.ma.utexas.edu/cgi-bin/man-cgi?convert+1)
Count and Find all IP connected to my host through TCP connection.
find all computer connected to my host through TCP connection
find all computer connected to my host through TCP connection.
count connections, group by IP and port