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commandlinefu.com is the place to record those command-line gems that you return to again and again. 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.

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Number of CPU's in a system
this works for a Linux based system, other UNIX systems may have other way(s) to check the number of CPUs.

Find files with the same names in several directories.
cat file1 file2 file3|sort|uniq -d finds the same lines in several files, especially in files with lists of files.

Forwards connections to your port 2000 to the port 22 of a remote host via ssh tunnel

Show max lengths of all fields in a pipe delimited file with header row

a function to find the fastest DNS server
http://public-dns.info gives a list of online dns servers. you need to change the country in url (br in this url) with your country code. this command need some time to ping all IP in list.

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Random Number Between 1 And 256
It takes a byte from /dev/random whose source is the kernel entropy pool (better source than other solutions).

Command line calculator
This function defines a command line calculator that handles everything pythons math module can handle, e.g. trigonometric functions, sqrt, log, erf, ... (see http://docs.python.org/library/math.html). It even knows about the constants pi and e.

Reverse SSHfs mount,
While `sshfs $REMOTE_HOST:$REMOTE_PATH $LOCAL_PATH` "pulls" a directory from the remote server to the local host, the above command does the reverse and "pushes" a directory from the local host to the remote server. This makes use of the "slave" option of sshfs which instructs it to communicate over plain stdin/stdout and the `dpipe` tool from vde2 to connect the sftp-server stdout to the sshfs stdin and vice-versa.

Clear terminal Screen
Probably the quickest / easiest way to clear the screen.


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