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 46
  • 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 14
  • 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 16
  • 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 36
  • 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 24
  • 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 45

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Print text string vertically, one character per line.

Binary clock
cryptic version

Remove security limitations from PDF documents using ghostscript (for Windows)
#4345 also works under windows

Annoying PROMPT_COMMAND animation
unset PROMPT_COMMAND to disable.

Alias to securely run X from tty and close that tty afterwards.
There are different ways to run X, I prefer to run it without xdm/gdm. The problem is you can't lock X because one can press Ctrl+Alt+F1, press Ctrl+Z and kill you X locking process. Of course you can disable Ctrl+Alt* or Ctrl+Alt+Backspace keys, but it's inconvinient if you really need to switch into console.

Get acurate memory usage of a Process in MegaBytes

Remove a line from a file using sed (useful for updating known SSH server keys when they change)
For example, to remove line 5 from foo, type: vi +5d +wq foo

Top ten (or whatever) memory utilizing processes (with children aggregate)
This command loops over all of the processes in a system and creates an associative array in awk with the process name as the key and the sum of the RSS as the value. The associative array has the effect of summing a parent process and all of it's children. It then prints the top ten processes sorted by size.

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

get you public ip address

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