Commands by jonty (6)

  • Use vi commands to edit your command lines

    If you spend all day editing in vi then switching your fingers to Emacs mode just for the command line can be difficult. Use set -o vi in your bash shell and enjoy the power of a real editor.


    1
    set -o vi; ls -l jnuk<ESC>bCjunk
    jonty · 2009-02-05 22:58:51 53
  • The simplest way to transport information over a network

    Einstein's razor: As simple as possible, but not simpler. On the destination machine netcat listens on any port (1234 in the example) and sends anything it receives into a file or pipe. On the source machine a separate netcat takes input from a file or pipe and sends it over the network to the listener. This is great between machines on a LAN where you don't care about authentication, encryption, or compression and I would recommend it for being simpler than anything else in this situation. Over the internet you should use something with better security.


    3
    (on destination machine) nc -l 1234 > whatever; (on source machine) nc destination 1234 < whatever;
    jonty · 2009-02-05 21:35:08 17
  • Getting started with tcpdump

    At some point you want to know what packets are flowing on your network. Use tcpdump for this. The man page is obtuse, to say the least, so here are some simple commands to get you started. -n means show IP numbers and don't try to translate them to names. -l means write a line as soon as it is ready. -i eth0 means trace the packets flowing through the first ethernet interface. src or dst w.x.y.z traces only packets going to or from IP address w.x.y.z. port 80 traces only packets for HTTP. proto udp traces only packets for UDP protocol. Once you are happy with each option combine them with 'and' 'or' 'not' to get the effects you want.


    2
    tcpdump -nli eth0; tcpdump -nli eth0 src or dst w.x.y.z; tcpdump -nli eth0 port 80; tcpdump -nli eth0 proto udp
    jonty · 2009-02-05 17:41:55 19
  • Start a new command in a new screen window

    If you are already running screen then you often want to start a command in a fresh window. You use this alias by typing 's whatever' from your command line and 'whatever' starts running in a new window. Good with interactive commands like info, vim, and nethack.


    19
    alias s='screen -X screen'; s top; s vi; s man ls;
    jonty · 2009-02-05 13:47:14 39
  • Get me yesterday's date, even if today is 1-Mar-2008 and yesterday was 29-Feb-2008

    Fool date by setting the timezone out by 24 hours and you get yesterday's date. Try TZ=XYZ-24 to get tomorrow's date. I live in TZ=GMT0BST so you might need to shift the number 24 by the hours in your timezone.


    1
    TZ=XYZ24 date
    jonty · 2009-02-05 13:27:14 26
  • Link all the files in this directory to that directory

    I find this handy for linking all the bin files in a package to /usr/bin or all the man files to /usr/share/man. You can replace * with */* to operate on all the files in subdirectories.


    0
    cd /this/directory; for f in *; do ln -s `pwd`/$f /that/directory; done
    jonty · 2009-02-05 13:21:16 48

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Bitcoin prices from the command line

Create sqlite db and store image
Creates a simple sqlite db (img.db) inserts /tmp/Q.jpg on base64 an recorvers it as /tmp/W.jpg

Simple server which listens on a port and prints out received data
Sometimes you need a simple server which listens on a port and prints out received data. Example: Consider you want to know, which data is posted by a homepage to a remote script without analysing the html code! A simple way to do this is to save the page to your computer, substitude all action="address" with action="localhost:portnumber", run 'ncat -l portnumber' and open the edited page with your browser. If you then submit the form, ncat will print out the http-protocol with all the posted data.

Benchmark SQL Query
Benchmark a SQL query against MySQL Server. The example runs the query 10 times, and you get the average runtime in the output. To ensure that the query does not get cached, use `RESET QUERY CACHE;` on top in the query file.

clear MyDNS-ng cache
Occasionally, to force zone updating, cache flush is necessary. This command is better than restart the mydns daemon.

Find files that are older than x days
Find files that are older than x days in the working directory and list them. This will recurse all the sub-directories inside the working directory. By changing the value for -mtime, you can adjust the time and by replacing the ls command with, say, rm, you can remove those files if you wish to.

put an unpacked .deb package back together
If any changes have been made to the package while it was unpacked (ie, conffiles files in /etc modi‐fied), the new package will inherit the changes. This way you can make it easy to copy packages from one computer to another, or to recreate packages that are installed on your system, but no longer available elsewhere. Note: dpkg-repack will place the created package in the current directory.

Cut flv video from minute 19 to minute 20 using flvtool2
We should calculate the video duration to milliseconds, 1 minute = 60000 milliseconds

Restart openssh-server on your Synology NAS from commandline.
The correct way to restart openssh-server on your synology nas.

Advanced python tracing
Trace python statement execution and syscalls invoked during that simultaneously

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