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  • Tail-recursive implementation of take-while

    - by Giorgio
    I am trying to write a tail-recursive implementation of the function take-while in Scheme (but this exercise can be done in another language as well). My first attempt was (define (take-while p xs) (if (or (null? xs) (not (p (car xs)))) '() (cons (car xs) (take-while p (cdr xs))))) which works correctly but is not tail-recursive. My next attempt was (define (take-while-tr p xs) (let loop ((acc '()) (ys xs)) (if (or (null? ys) (not (p (car ys)))) (reverse acc) (loop (cons (car ys) acc) (cdr ys))))) which is tail recursive but needs a call to reverse as a last step in order to return the result list in the proper order. I cannot come up with a solution that is tail-recursive, does not use reverse, only uses lists as data structure (using a functional data structure like a Haskell's sequence which allows to append elements is not an option), has complexity linear in the size of the prefix, or at least does not have quadratic complexity (thanks to delnan for pointing this out). Is there an alternative solution satisfying all the properties above? My intuition tells me that it is impossible to accumulate the prefix of a list in a tail-recursive fashion while maintaining the original order between the elements (i.e. without the need of using reverse to adjust the result) but I am not able to prove this. Note The solution using reverse satisfies conditions 1, 3, 4.

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  • tail stops displaying in case of a log rotation

    - by Rudy Vissers
    I have to tail the log of a server (servicemix) and the log rotation is enabled. As soon as the rotation happens, tail stops displaying. I did some investigations and it is a bug in Debian : Debian Bug Report. The bug has been around for a long time ago. Does anyone knows if this bug in Ubuntu is to be fixed? I'm on Ubuntu 12.04 64 bit. I don't have to mention that this bug is total hell! Every time I have the problem, I have to interrupt the command tail and re-execute the command!

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  • Does MATLAB perform tail call optimization?

    - by Shea Levy
    I've recently learned Haskell, and am trying to carry the pure functional style over to my other code when possible. An important aspect of this is treating all variables as immutable, i.e. constants. In order to do so, many computations that would be implemented using loops in an imperative style have to be performed using recursion, which typically incurs a memory penalty due to the allocation a new stack frame for each function call. In the special case of a tail call (where the return value of a called function is immediately returned to the callee's caller), however, this penalty can be bypassed by a process called tail call optimization (in one method, this can be done by essentially replacing a call with a jmp after setting up the stack properly). Does MATLAB perform TCO by default, or is there a way to tell it to?

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  • GUI for watching logs (tail and grep)

    - by Grzegorz Oledzki
    Could you recommend a GUI application with powerful log watching capabilities? Generally it would work as tail -f in GUI, but on top of that following features would be very useful: filtering out some lines based on (regular) expressions coloring some lines based on (regular) expressions interactive search saveable configuration easily applicable to different files notifications based on (regular) expressions A similar tool on Windows is BareTail and its paid version - BareTailPro

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  • GUI for watching logs (tail and grep)

    - by Grzegorz Oledzki
    Could you recommend a GUI application with powerful log watching capabilities? Generally it would work as tail -f in GUI, but on top of that following features would be very useful: filtering out some lines based on (regular) expressions coloring some lines based on (regular) expressions interactive search saveable configuration easily applicable to different files notifications based on (regular) expressions A similar tool on Windows is BareTail and its paid version - BareTailPro

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  • tail -f and then exit on matching string

    - by Patrick
    I am trying to configure a startup script which will startup tomcat, monitor the catalina.out for the string "Server startup", and then run another process. I have been trying various combinations of tail -f with grep and awk, but haven't got anything working yet. The main issue I am having seems to be with forcing the tail to die after grep or awk have matched the string. I have simplified to the following test case. test.sh is listed below: #!/bin/sh rm -f child.out ./child.sh > child.out & tail -f child.out | grep -q B child.sh is listed below: #!/bin/sh echo A sleep 20 echo B echo C sleep 40 echo D The behavior I am seeing is that grep exits after 20 seconds , however the tail will take a further 40 seconds to die. I understand why this is happening - tail will only notice that the pipe is gone when it writes to it which only happens when data gets appended to the file. This is compounded by the fact that tail is to be buffering the data and outputting the B and C characters as a single write (I confirmed this by strace). I have attempted to fix that with solutions I found elsewhere, such as using unbuffer command, but that didn't help. Anybody got any ideas for how to get this working how I expect it? Or ideas for waiting for successful Tomcat start (thinking about waiting for a TCP port to know it has started, but suspect that will become more complex that what I am trying to do now). I have managed to get it working with awk doing a "killall tail" on match, but I am not happy with that solution. Note I am trying to get this to work on RHEL4.

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  • tail -f and then exit on matching string

    - by Patrick
    I am trying to configure a startup script which will startup tomcat, monitor the catalina.out for the string "Server startup", and then run another process. I have been trying various combinations of tail -f with grep and awk, but haven't got anything working yet. The main issue I am having seems to be with forcing the tail to die after grep or awk have matched the string. I have simplified to the following test case. test.sh is listed below: #!/bin/sh rm -f child.out ./child.sh > child.out & tail -f child.out | grep -q B child.sh is listed below: #!/bin/sh echo A sleep 20 echo B echo C sleep 40 echo D The behavior I am seeing is that grep exits after 20 seconds , however the tail will take a further 40 seconds to die. I understand why this is happening - tail will only notice that the pipe is gone when it writes to it which only happens when data gets appended to the file. This is compounded by the fact that tail is to be buffering the data and outputting the B and C characters as a single write (I confirmed this by strace). I have attempted to fix that with solutions I found elsewhere, such as using unbuffer command, but that didn't help. Anybody got any ideas for how to get this working how I expect it? Or ideas for waiting for successful Tomcat start (thinking about waiting for a TCP port to know it has started, but suspect that will become more complex that what I am trying to do now). I have managed to get it working with awk doing a "killall tail" on match, but I am not happy with that solution. Note I am trying to get this to work on RHEL4.

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  • How to set up a mini call center?

    - by Ralph
    I'm trying to figure out how to set up a miniature call center for a small business. Like, for 1-4 people to take calls, but hopefully expandable to more. We want to accept nation-wide calls, and then I guess distribute the calls among the available agents. If no one is available, I guess it should either put them in a queue and play some annoying music for them, or forward to call to an agent who has least-recently taken a call who can then quickly answer and say "please hold" until they're done their call. We want to have one phone number that customers can call. I guess we then need some kind of ACD system which would take each call and forward it to an agent based on some algorithm? Then we would need to purchase a separate phone line for each agent, plus one just for the distributor? Or do we need several "extra" lines to maintain a queue (one for each customer waiting too)? This "ACD" thing, is it just a device that you would plug a phone line into (or several?), and maybe connect to a computer, aided by some software? Or is a subscription thing that I would need from my local telephone provider? Next, the business we're running, the callers will be repeat customers. It would be helpful to automatically pull up their profile based on the incoming number. The "software" our agents will be running will just be a website where they can log in (preferably from home) and then enter some information they would obtain through the call. So, the system would have to somehow interface with the website if possible. If not, we'll just have to ask each customer for an identifier (phone number, username, customer number, or something). Is this possible? I guess each computer would need a device that the call would pass through, and then if I can somehow hook into that, then I can write some software that will interface with the site. So, where do I start? What hardware do we need to buy? What subscriptions do we need? We were thinking this magicJack might help us in accepting long-distance calls for cheaper, but my understanding is that they provide you with some weird-looking number, is there a way we could "mask" it with our toll-free number? And then pass the incoming calls through the distributor system, which would then get passed to the call-accepting device which would both allow an agent to answer the call and have a software hook? (I realize this might be partially out of the scope of SU, but I wasn't sure where else to ask. It is about computer(-aided) hardware and software anyway.) P.S.: I don't need any of that "press 1 to talk to..." or "say xyz to..." junk. Just a straight-forward, connect-to-next-available-agent system.

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  • Don’t miss this very popular presentation on Punchout in iProcurement on June 26th 2012

    - by user793553
    Don’t miss this very popular presentation on Punchout in iProcurement on June 26th.  See Doc ID 1448447.1 for the Webcast details. ADVISOR WEBCAST: Punchout in iProcurement PRODUCT FAMILY: EBZs- Procurement   June 26, 2012 at 14:00 UK / 15:00 Cairo / 6:00 am Pacific / 7:00 am Mountain / 9:00 am Eastern This one-hour session is recommended for technical and functional users who are maintaining and/or implementing the Punchout from iProcurement. The session will provide an overview of the different Punchout model, setup, and the Punchout to PO xml/cxml cycle. Also, it will provide tips in troubleshooting the common issues when new supplier is added to Punchout or the existing one stops working. TOPICS WILL INCLUDE: Overview of the Punchout Models. Provide the knowledge in the Punchout to PO Process cycle. Demo - Punchout. Certificates and setup. Learn the common issues and how to address in an efficient way. (Documentation and Notes) A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services. Current Schedule can be found on Note 740966.1 Post Presentation Recordings can be found on Note 740964.1 WebEx Conference Details Topic: Advisor Webcast - Punchout in iProcuremen Date and Time: Tuesday, June 26, 2012 3:00 pm, Egypt Time (Cairo, GMT+02:00) Tuesday, June 26, 2012 2:00 pm, GMT Summer Time (London, GMT+01:00) Tuesday, June 26, 2012 9:00 am, Eastern Daylight Time (New York, GMT-04:00) Tuesday, June 26, 2012 7:00 am, Mountain Daylight Time (Denver, GMT-06:00) Event number: 597 373 155 -------------------------------------------------------  To register for this meeting  -------------------------------------------------------  1. Event address for attendees: https://oracleaw.webex.com/oracleaw/onstage/g.php?d=597373155&t=a 2. Register for the meeting.  Once the host approves your request, you will receive a confirmation email with instructions for joining the meeting. InterCall Audio Instructions A list of Toll-Free Numbers can be found below. VOICESTREAMING IS AVAILABLE teleconference ID: 70528713 UK standard International:+44 1452 562 665 US Free Call: 1866 230 1938 US Local call: 1845 608 8023 Global Toll-Free Numbers MOS doc#:  https://metalink3.oracle.com/od/faces/secure/km/DocumentDisplay.jspx?id=1148600.1 Designation Number Argentina Free Call 0800 444 1009 Australia Free Call 1800 763 650 Austria Free Call 0800 111 956 Austria Local Call 0192 865 72 Belgium Free Call 0800 724 46 Belgium Local Call 0817 000 60 Brazil Free Call 0800 761 0835 Bulgaria Free Call 0080 011 511 76 Canada Free Call 1866 984 6577 Columbia Free Call 0180 091 562 17 Croatia Free Call 0800 222 305 Cyprus Free Call 8009 6341 Czech Republic Free Call 8007 007 95 Denmark Free Call 8088 8467 Denmark Local Call 3272 7506 Finland Free Call 0800 112 398 Finland Local Call 0923 114 014 France Free Call 0805 110 463 France Local Call 0359 580 290 Germany Free Call 0800 101 4918 Germany Local Call 0692 222 161 19 Greece Free Call 0080 012 8135 Hong Kong Free Call 8009 661 55 Hungary Free Call 0680 018 839 Hungary Local Call 0180 889 97 India Free Call 0008 001 006 600 Ireland Free Call 1800 300 170 Ireland Local Call 0143 198 35 Israel Free Call 1809 431 440 Italy Free Call 8007 840 87 Italy Local Call 0236 009 700 Japan Free Call 0066 338 124 31 Latvia Free Call 8000 3680 Luxembourg Free Call 8002 7941 Malaysia Free Call 1800 814 528 Mexico Free Call 0018 666 864 905 Monaco Free Call 8009 3655 Netherlands Free Call 0800 949 4596 Netherlands Local Call 0207 168 000 New Zealand Free Call 0800 451 190 North China Free Call 1080 074 413 29 Norway Free Call 8001 8057 Norway Local Call 2151 0847 Poland Free Call 0080 012 135 73 Portugal Free Call 8007 894 20 Romania Free Call 0800 895 558 Russia Free Call 8108 002 385 2044 Slovenia Free Call 0800 804 55 South Africa Free Call 0800 982 794 South China Free Call 1080 044 111 82 South Korea Free Call 0079 814 800 7887 Spain Free Call 9009 389 85 Spain Local Call 9111 421 10 Sweden Free Call 0200 214 344 Sweden Local Call 0850 596 375 Switzerland Free Call 0800 835 040 Switzerland Local Call 0445 804 280 Thailand Free Call 0018 004 421 98 UK Free Call 0800 073 1830 UK Local Call 0844 871 9364 UK National Call 0871 700 0309 UK Standard International +44 (0) 1452 562 665 USA Free Call 1866 230 1938   Back to the top   Copyright? 2010, Oracle. All rights reserved. Contact Us | Legal Notices and Terms of Use | Privacy Statement

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  • Tail the filename, not the file

    - by Craig Walker
    In UNIX (OS X BSD to be precise), I have a "tail -f" command on a log file. From time to time I want to delete this log file so I can more easily review it in my text editor. I delete the file, and then my program recreates it after new activity. However, my tail command (and anything else that was watching the old log file) doesn't update; it's still watching the old, deleted log file. I think I understand why this is (file names simply being pointers to blocks of file data). I'd like to know how I can work around this. Ideally, my tail command (and anything else I point to the file) would be able to read the data from the new file when the file name has been deleted and recreated. How would I do this?

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  • How to watch for count of new lines in tail

    - by fl00r
    I want to do something like this: watch tail -f | wc -l #=> 43 #=> 56 #=> 61 #=> 44 #=> ... It counts new lines of tail each second / Linux, CentOs To be more clear. I have got something like this: tail -f /var/log/my_process/*.log | grep error I am reading some error messages. And now I want to count them. How many ~ errors I have got in a second. So one line in a log is one error in a proccess.

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  • tail -f updates slowly

    - by Cliff
    I'm not sure why, but on my Macbook Pro running lion I get slow updates when I issue "tail -f" on a log file that is being written to. I used to use this command all the time at my last company but that was typically on Linux machines. The only thing I can think of that would possibly slow the updates are buffering of output and/or maybe a different update interval on a Mac vs. Linux. I've tried with several commands all which write to stout relatively quickly but give slow updates to the tail command. Any ideas? Update I am merely running a python script with a bunch of prints in it and redirecting to a file vi " my output.log". I expect to see updates near real time but that doesn't seem to be the case.

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  • Should not a tail-recursive function also be faster?

    - by Balint Erdi
    I have the following Clojure code to calculate a number with a certain "factorable" property. (what exactly the code does is secondary). (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (factor-9 (quot n 10)))))) Now, I'm into TCO and realize that Clojure can only provide tail-recursion if explicitly told so using the recur keyword. So I've rewritten the code to do that (replacing factor-9 with recur being the only difference): (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (recur (quot n 10)))))) To my knowledge, TCO has a double benefit. The first one is that it does not use the stack as heavily as a non tail-recursive call and thus does not blow it on larger recursions. The second, I think is that consequently it's faster since it can be converted to a loop. Now, I've made a very rough benchmark and have not seen any difference between the two implementations although. Am I wrong in my second assumption or does this have something to do with running on the JVM (which does not have automatic TCO) and recur using a trick to achieve it? Thank you.

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  • Adding tail behaviour where enter adds blank lines to less

    - by gonvaled
    I love less, which I can use to follow logs with the +F flag (or the ShiftF hotkey), search forwards and backwards, and generally move freely through the document. But there is one thing missing in less: usually I am at the end of the file, and I want to see new things happening. In tail -f I would just hit enter several times, and new log lines would just appear clearly separated from old lines. Is it possible to add this to less? How?

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  • Best tools for "ssh tail -f" style log file monitoring and analysis

    - by dougnukem
    I'm looking for a tool to monitor custom PHP Error logs/Apache and possibly Java logs on remote development servers. I'm not looking for a full production log system like Splunk, but something that's a little more flexible than an ssh terminal doing a "tail -f". Perhaps something that will: * Monitor multiple log files to my local machine for searching/analysis later * Allow "alerts" when certain strings appear in the log * Provide some kind of tabbed/dashboard view of the multiple logs being monitored (in total less than 10 logs).

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  • Tail-recursive merge sort in OCaml

    - by CFP
    Hello world! I’m trying to implement a tail-recursive list-sorting function in OCaml, and I’ve come up with the following code: let tailrec_merge_sort l = let split l = let rec _split source left right = match source with | [] -> (left, right) | head :: tail -> _split tail right (head :: left) in _split l [] [] in let merge l1 l2 = let rec _merge l1 l2 result = match l1, l2 with | [], [] -> result | [], h :: t | h :: t, [] -> _merge [] t (h :: result) | h1 :: t1, h2 :: t2 -> if h1 < h2 then _merge t1 l2 (h1 :: result) else _merge l1 t2 (h2 :: result) in List.rev (_merge l1 l2 []) in let rec sort = function | [] -> [] | [a] -> [a] | list -> let left, right = split list in merge (sort left) (sort right) in sort l ;; Yet it seems that it is not actually tail-recursive, since I encounter a "Stack overflow during evaluation (looping recursion?)" error. Could you please help me spot the non tail-recursive call in this code? I've searched quite a lot, without finding it. Cout it be the let binding in the sort function? Thanks a lot, CFP.

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  • Tail recursion in C++

    - by Phenom
    Can someone show me a simple tail-recursive function in C++? Why is tail recursion better, if it even is? What other kinds of recursion are there besides tail recursion?

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  • NSTask Tail -f Using objective C

    - by Bach
    I need to read the last added line to a log file, in realtime, and capture that line being added. Something similar to Tail -f. So my first attempt was to use Tail -f using NSTask. I can't see any output using the code below: NSTask *server = [[NSTask alloc] init]; [server setLaunchPath:@"/usr/bin/tail"]; [server setArguments:[NSArray arrayWithObjects:@"-f", @"/path/to/my/LogFile.txt",nil]]; NSPipe *outputPipe = [NSPipe pipe]; [server setStandardInput:[NSPipe pipe]]; [server setStandardOutput:outputPipe]; [server launch]; [server waitUntilExit]; [server release]; NSData *outputData = [[outputPipe fileHandleForReading] readDataToEndOfFile]; NSString *outputString = [[[NSString alloc] initWithData:outputData encoding:NSUTF8StringEncoding] autorelease]; NSLog (@"Output \n%@", outputString); I can see the output as expected when using: [server setLaunchPath:@"/bin/ls"]; How can i capture the output of that tail NSTask? Is there any alternative to this method, where I can open a stream to file and each time a line is added, output it on screen? (basic logging functionality)

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  • Get last n lines of a file with Python, similar to tail

    - by Armin Ronacher
    I'm writing a log file viewer for a web application and for that I want to paginate through the lines of the log file. The items in the file are line based with the newest item on the bottom. So I need a tail() method that can read n lines from the bottom and supports an offset. What I came up with looks like this: def tail(f, n, offset=0): """Reads a n lines from f with an offset of offset lines.""" avg_line_length = 74 to_read = n + offset while 1: try: f.seek(-(avg_line_length * to_read), 2) except IOError: # woops. apparently file is smaller than what we want # to step back, go to the beginning instead f.seek(0) pos = f.tell() lines = f.read().splitlines() if len(lines) >= to_read or pos == 0: return lines[-to_read:offset and -offset or None] avg_line_length *= 1.3 Is this a reasonable approach? What is the recommended way to tail log files with offsets?

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  • Ending tail -f started in a shell script

    - by rangalo
    I have the following. A Java process writing logs to the stdout A shell script starting the Java process Another shell script which executes the previous one and redirects the log I check the log file with the tail -f command for the success message. Even if I have exit 0 in the code I cannot end the tail -f process. Which doesn't let my script to finish. Is there any other way of doing this in Bash? The code looks like the following. function startServer() { touch logfile startJavaprocess > logfile & tail -f logfile | while read line do if echo $line | grep -q 'Started'; then echo 'Server Started' exit 0 fi done }

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  • Using JSP to Tail a file

    - by nick
    Is there a way to use JSP to create a file tail like Linux's "tail -f" and cache the results? That is, can I read the last X items, cache, and then read again if I get a request that exceeds some timeout?

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  • EU Research for ICT - Call 7 - biggest ever at € 780 million

    - by trond-arne.undheim
    Under the Digital Agenda for Europe, the Commission has committed to maintaining the pace of a 20% yearly increase of the annual ICT R&D budget at least until 2013. The EU's flagship policy programme calls for doubling of annual public spending on ICT R&D by 2020 and to leverage an equivalent increase in private spending to achieve the goals of Europe's 2020 strategy for jobs and growth. Call 7 is one of the biggest calls ever launched for information and communications technology (ICT) research proposals under the EU's research framework programmes. It will result in project funding of € 780 million in 2011. This funding will advance research on the future internet, robotics, smart and embedded systems, photonics, ICT for energy efficiency, health and well-being in an ageing society, and more. The €780 million call for proposals is part of the biggest ever annual Work Programme under the EU's 7th Framework Programme for Research. Almost €1.2 billion has been budgeted for 2011. €220 million were made available already in July 2010 for public private partnerships focusing on ICT for smart cars, green buildings, sustainable factories and the future internet. Universities, research centres, SMEs, large companies and other organisations in Europe and beyond are eligible to apply for project funding under ICT Call 7. Proposals can be submitted until 18 January 2011, after which they will be evaluated by independent panels of experts for selection on the basis of their quality. Background: Digital Agenda: European Commission announces €780 million boost for strategic ICT research. Call text: ICT Call 7 Deadline: 18/01/2011.

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  • CRM at Oracle Series: Do Not Call & Do Not Email

    - by tony.berk
    Who you gonna call? Or not call! Sorry, just kidding, this isn't a movie blog! Do Not Call is an important topic for all businesses as there are government regulations that can lead to significant fines, and of course, possible damage to your brand. Oracle leverages Siebel CRM to develop an effective solution to address the Do Not Call and Email Permissible Use requirements. The application uses the Contacts functionality to manage communication preferences, which when defined, centrally synchronizes all contact records that share the same phone number and email address. Additionally, the relevant information is masked so Oracle employees cannot accidentally reach out to the contact. Therefore, the solution ensures that we are compliant with regulations, enables us to respect individuals' communication preferences and provides an audit trail of changes to their preferences. Today's CRM at Oracle slidecast discusses the requirements, highlights benefits and provides screen shots of the solution. CRM at Oracle Series: Do Not Call & Do Not Email Click here to learn more about Siebel CRM and other Oracle CRM products. Are you enjoying the CRM at Oracle Series? We are working on more topics for this year, but if there is a particular CRM area or function which you'd like to hear how Oracle implemented it internally, leave us a comment and we'll try to get it on our list.

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  • SEO & SEM Long Tail Keyword Marketing Strategy

    Long tail marketing strategies for SEO & SEM often return higher conversion rates by up to 200% as compared to short tail generic keyword terms. These long tail keyword terms can be extremely profitable for SEM (search engine marketing) in terms of lower cost or bid for keywords and larger returns on pay per click investment.

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