Using netcat, usuallly installed on debian/ubuntu. Also to test against a sample server the following two commands may help echo got milk? | netcat -l -p 25 python -c "import SocketServer; SocketServer.BaseRequestHandler.handle = lambda self: self.request.send('got milk?\n'); SocketServer.TCPServer(('0.0.0.0', 25), SocketServer.BaseRequestHandler).serve_forever()" Show Sample Output
this command will send a message to the socket 25 on host 192.168.1.2 in tcp. works on udp and icmp understand only IP address, not hostname. on the other side (192.168.1.2), you can listen to this socket and test if you receive the message. easy to diagnose a firewall problem or not.
Searches in order of the directories of $PATH. Stops after finding the entry; looks for only that fileName. Works in Bourne, Korn, Bash and Z shells. Show Sample Output
search argument in PATH accept grep expressions without args, list all binaries found in PATH Show Sample Output
Define a function
vert () { echo $1 | grep -o '.'; }
Use it to print some column headers
paste <(vert several) <(vert parallel) <(vert vertical) <(vert "lines of") <(vert "text can") <(vert "be used") <(vert "for labels") <(vert "for columns") <(vert "of numbers")
Show Sample Output
EDIT: Trolling crap removed ;)
takes approx 6 secs on a Core 2 Duo @ 2GHz, and 15 secs on atom based netbooks!
uses monoid (a,b).(x,y)=(ax+bx+ay,ax+by) with identity (0,1), and recursion relations:
F(2n-1)=Fn*Fn+F(n-1)*F(n-1)
F(2n)=(Fn+2*F(n-1))*Fn
then apply fast exponentiation to (1,0)^n = (Fn,F(n-1))
.
Note that: (1,0)^-1=(1,-1) so (a,b).(1,0) = (a+b,a) and (a,b)/(1,0)=(a,b).(1,0)^-1=(b,a-b)
So we can also use a NAF representation to do the exponentiation,http://en.wikipedia.org/wiki/Non-adjacent_form , it's also very fast (about the same, depends on n):
time echo 'n=1000000;m=(n+1)/2;a=0;b=1;i=0;while(m>0){z=0;if(m%2)z=2-(m%4);m=(m-z)/2;e[i++]=z};while(i--){c=a*a;a=c+2*a*b;b=c+b*b;if(e[i]>0){t=a;a+=b;b=t};if(e[i]<0){t=a;a=b;b=t-b}};if(n%2)a*a+b*b;if(!n%2)a*(a+2*b)' | bc
Show Sample Output
Calculates nth Fibonacci number for all n>=0, (much faster than matrix power algorithm from http://everything2.com/title/Compute+Fibonacci+numbers+FAST%2521 )
n=70332 is the biggest value at http://bigprimes.net/archive/fibonacci/ (corresponds to n=70331 there), this calculates it in less than a second, even on a netbook.
UPDATE: Now even faster! Uses recurrence relation for F(2n), see http://en.wikipedia.org/wiki/Fibonacci_number#Matrix_form
n is now adjusted to match Fn at wikipedia, so bigprimes.net table is offset by 1.
UPDATE2: Probably fastest possible now ;), uses a simple monoid operation:
uses monoid (a,b).(x,y)=(ax+bx+ay,ax+by) with identity (0,1), and recursion relations:
F(2n-1)=Fn*Fn+F(n-1)*F(n-1)
F(2n)=Fn*(2*F(n-1)+Fn)
then apply fast exponentiation to (1,0)^n = (Fn,F(n-1))
.
Note that: (1,0)^-1=(1,-1) so (a,b).(1,0) = (a+b,a) and (a,b)/(1,0)=(a,b).(1,0)^-1=(b,a-b)
So we can also use a NAF representation to do the exponentiation,http://en.wikipedia.org/wiki/Non-adjacent_form , it's also very fast (about the same, depends on n):
time echo 'n=70332;m=(n+1)/2;a=0;b=1;i=0;while(m>0){z=0;if(m%2)z=2-(m%4);m=(m-z)/2;e[i++]=z};while(i--){c=a*a;a=c+2*a*b;b=c+b*b;if(e[i]>0){t=a;a+=b;b=t};if(e[i]<0){t=a;a=b;b=t-b}};if(n%2)a*a+b*b;if(!n%2)a*(a+2*b)' | bc
Show Sample Output
OS: Debian based (or those that use dpkg) Equivalent to doing a dpkg -S on each file in $PATH, but way faster. May report files generated though postinstall scripts and such. For example . It will report /usr/bin/vim .. which is not not a file installed directly by dpkg, but a link generated by alternatives hooks
Removes trailing newline; colon becomes record separator and newline becomes field separator, only the first field is ever printed. Replaces empty entries with $PWD. Also prepend relative directories (like ".") with the current directory ($PWD). Can change PWD with env(1) to get tricky in (non-Bourne) scripts. Show Sample Output
This version uses Pipes, but is easier for the common user to grasp... instead of using sed or some other more complicated method, it uses the tr command Show Sample Output
[Note: This command needs to be run as root]. If you are downloading something large at night, you can start wget as a normal user and issue the above command as root. When the download is done, the computer will automatically go to sleep. If at any time you feel the computer should not go to sleep automatically(like if you find the download still continuing in the morning), just create an empty file called nosleep in /tmp directory.
A very simple command to send a signed and encrypted message from the command line using GPG Keys
Based on the MrMerry one, just add some visuals to differentiate files and directories
Based on the MrMerry one, just add some visuals and sort directory and files
another possibility
using awk missed the last char thanks @Josay Show Sample Output
Can change language and speed, see espeak man page for options. (Install espeak in your linux distro via yum or apt-get) For insomniacs you may need to enclose in a while true; do ...; done loop ;) Show Sample Output
Sorts a character string, using common shell commands. Show Sample Output
using bc is for sissies. dc is much better :-D Polish notation will rule the world... Show Sample Output
you can also run "xmms2 pause & at now +5min
Shorter version. Show Sample Output
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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