May 2012 - main - earth.li

Renaming of files failing
by Chris Walker 17 Dec '12

17 Dec '12

I have a directory full of files and sub-directories which I've pulled from an emulator. But it has extra filename extensions on it. I would like to traverse this directory, stripping off the extensions and so I've been trying to write a script to do it but it's failing. An example of a file is this :- lamborghini miura_1024.jpg,c85 and so there, I'd like to remove the ,c85. But a bigger problem is where I have the odd file which has a numeric extensions such as .;1 and that's where I struggle. How do I do a substitution in my script to cope with things like that? I've been reading things like this - http://www.cyberciti.biz/tips/renaming-multiple-files-at-a-shell-prompt.html and http://www.unix.com/answers-frequently-asked-questions/13774-unix-tutorials… but I'm still struggling. Can somebody point me in the right direction please, even if it's towards the door ;-) -- __ __| |_ __ __ .----------------------------------------------. / _/ _` \ V V / | mailto:cdw_alug@the-walker-household.co.uk | \__\__,_|\_/\_/ |______________________________________________|

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Keyboard and mouse 'crash'
by Bev Nicolson 19 Aug '12

19 Aug '12

Every so often (not too often happily) both keyboard and mouse will stop functioning. It seems to happen most often when I plug a camera or MP3 player in. The only way to get them going again is to switch everything off. (If I touch the off button it will shut down in 60 seconds from the shut down dialogue box.) What I'm wondering is, has anyone here come across this problem and is there another, more permanent, solution to it? I would add that I've never had to install any drivers for any such devices, so I'm pretty confident that's not the issue. [Unbuntu 11.04.] Bev.

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deb/alien dependencies
by Mark Rogers 11 Jul '12

11 Jul '12

I'm trying to install hamachi [1] on Debian (arm). I want the smallest install I can get away with, but at the moment I'm getting the following dependencies: alien at autopoint bc binutils build-essential bzip2 cpp cpp-4.4 cups-bsd cups-client cups-common debhelper dpkg-dev fakeroot g++ g++-4.4 gcc gcc-4.4 gettext gettext-base git html2text intltool-debian libalgorithm-diff-perl libalgorithm-diff-xs-perl libalgorithm-merge-perl libc-dev-bin libc6-dev libcurl3-gnutls libdpkg-perl libelf1 liberror-perl libgmp3c2 liblua5.1-0 libmail-sendmail-perl libmpfr4 libnspr4-0d libnss3-1d librpm1 librpmbuild1 librpmio1 libstdc++6-4.4-dev libsys-hostname-long-perl libtimedate-perl libunistring0 linux-libc-dev lsb-core lsb-release m4 make manpages-dev ncurses-term patch pax po-debconf rpm rpm-common rpm2cpio time It installs and runs OK but I don't want all that stuff on my box afterwards! Seeing alien in the list makes me conclude that this is a repackaged rpm and maybe that's what's causing the problem. However if I try to "apt-get remove alien" afterwards, hamachi gets removed. What are my options to work around this? Unfortunately Hamachi is not free and therefore I don't have access to the source. [1] https://secure.logmein.com/labs/ -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER

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Email clients! - Alpine... anyone use it?
by James Freer 04 Jun '12

04 Jun '12

For a while i've just used the browser for email having found Thunderbird, Evolution and similar so slow on imap. Mutt i managed to set up but being so configurable wasn't to my liking. Alpine seems the fastest of any i've tried... easy to setup - just wondering if anyone else on here uses it. If they do any problems? jmaes

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How to print stupid Royal Mail price list?
by Chris Green 01 Jun '12

01 Jun '12

The Royal Mail used to provide a neat PDF file which fitted A4 to show their postage prices. The latest version though is a 'booklet' so I can't see any way to actually print it on an A4 printer. This is the link to the PDF:- http://c435158.r58.cf3.rackcdn.com/Royal_Mail_Our_Prices.pdf Can anyone tell me how to split it up into printable pages? I've tried ImageMagick's convert but that didn't default to what I wanted, maybe I need some more options to tell it what to do. -- Chris Green

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Programming question - different approaches to classic command parsing
by Chris Green 29 May '12

29 May '12

Well my Nanode project is progressing (it's the one that has the rather idiosyncratic ethernet handling). The next question is whether to rejig the basic command handling. The Nanode software I'm maintaining/improving is basically very simple, after initialisation it waits for an ethernet UDP packet with a command code and data in it, then it acts on the command and returns (via UDP again) some sort of response. There are currently 34 commands, this will expand somewhat but is unlikely to ever be more than 100 or so. The existing code simply has a switch/case block switching on the command code with the cases handling each command. It's a bit long but is manageable. I'm wondering whether to stay with the existing structure or to go to some sort of table driven approach with an array of something like:- // // // Command table entry structure // struct command { uint32_t cmd; // the command code int (* fnc) (int addr); // the address of the function to call char * str; // the associated LCD string }; (obviously the function parameters may extend/change) A linear search of an array of these won't waste much time, speed isn't of great consequence anyway. Then each command will be a function, tidier and more modular, but will it actually win me anything (or lose anything)? In particular will it use more space, in code or RAM? In code there will be, say, 50 function calls plus a table instead of a switch statement with 50 case: blocks. In RAM there will be lots of smaller functions using a small amount of stack space instead of one big one with lots of local variables. This is using the gcc-avr compiler by the way. My gut feeling is that it probably won't make a big difference either in code space use or in RAM use but it will probably use a little bit more of both. The question then is whether the significant amount of rewriting is worth it for the more elegant (and hence easy to maintain) code. If there's another approach to managing this sort of command driven interface then I'd be interested in hearing about it. -- Chris Green

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Re: [ALUG] Ethernet programming question
by Phil Ashby 28 May '12

28 May '12

Chris Green <cl(a)isbd.net> wrote: > I'm doing some programming of a Nanode board (not far removed from > Arduino) which has an ethernet interface based on the ENC28J60. > ... > However the loop that waits for ethernet packets and deals with them > seems a bit odd to me, in psuedo-code it's something like:- > > while (not reset) > { > get a packet from ethernet > > handle DHCP message > > handle message requesting local display on LCD > > handle ARP request > > handle DNS request > > handle NTP request > > if (still something left) > { > if (ping) > { > respond to ping > } > if (UDP message for us) > { > handle our message > } > } > } > > > What I'm not clear about is whether one packet can only be one of the > above things. Hence, if a DHCP request of some sort has been received > and handled can the *same* packet contain other requests? If not then > why is the code going through all the other calls? Hi Chris - you are correct in assuming that one packet can only be one thing, since a combination of packet type fields (Ethernet frame type, IP frame type, TCP/UDP port number) determine this. > OK, it makes for simpler looking code, no conditionals and/or > switch/case but it somehow seems wrong (and a bit inefficient as each > handle function gets called even if the packet has already been > handled). Just been and looked at the code in github for the Nanode Ethershield and all I can say is yuk! https://github.com/Nanode/EtherShield/blob/master/ip_arp_udp_tcp.c I quote: "The TCP implementation uses some size optimisations which are valid only if all data can be sent in one single packet. This is however not a big limitation for a microcontroller as you will anyhow use small web-pages." Hmmn. I found the code confusing, badly structured and incomplete (eg: it doesn't work if IP options are sent and there is nothing like the full TCP state machine with various timers, backoff controls and such, only a happy path). Of course I may have been looking at different code - got a URL? Phil. PS: http://code.google.com/p/avr-uip/ looks rather better!

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Ethernet programming question
by Chris Green 28 May '12

28 May '12

I'm doing some programming of a Nanode board (not far removed from Arduino) which has an ethernet interface based on the ENC28J60. I'm only modifying the existing software rather than building from scratch but would like to tidy things as much as possible. The ethernet initialisation etc. is standard library code so is cast in stone as it were but I'm puzzling over the higher level ethernet message handling stuff a bit. The system basically handles incoming requests sent over the ethernet interface and replies with instrument data, this part of the code is pretty straightforward. However the loop that waits for ethernet packets and deals with them seems a bit odd to me, in psuedo-code it's something like:- while (not reset) { get a packet from ethernet handle DHCP message handle message requesting local display on LCD handle ARP request handle DNS request handle NTP request if (still something left) { if (ping) { respond to ping } if (UDP message for us) { handle our message } } } What I'm not clear about is whether one packet can only be one of the above things. Hence, if a DHCP request of some sort has been received and handled can the *same* packet contain other requests? If not then why is the code going through all the other calls? OK, it makes for simpler looking code, no conditionals and/or switch/case but it somehow seems wrong (and a bit inefficient as each handle function gets called even if the packet has already been handled). -- Chris Green

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Ripping MP3s
by Chris Walker 23 May '12

23 May '12

I have a Creative Zen MP3 player which I use in my car. I want to tidy up a load of CDs which have accumulated over the years before they go to the bin. They're freebies from newspapers and so aren't worth anything and have the usual half dozen decent tracks followed a dozen rubbish tracks. But I'm stuck trying to rip them to MP3. I've tried k3b but that doesn't offer MP3 as an output option. I've also installed soundkonverter (rather than soundconverter as I'm using kde for a desktop) but despite saying that it can use FFmpeg as a plugin, there is still no MP3 option. Am I doing something wrong? The system is Mandriva 2011 64 bit.

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[very off topic] drill press
by David Reynolds 22 May '12

22 May '12

Hi guys, Does anyone in the Norwich-ish area happen to have (or have access to) a drill press I could use? I am building a guitar from a kit and I need to drill 4 holes with said drill press. Can anyone help? -- David Reynolds david(a)reynoldsfamily.org.uk

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