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  • Linux - Programmatically write to a proc file

    - by Zach
    I have found several examples online where we can create a proc file, assign read and write methods that are called every time the proc file is opened for read or written to. However, I can't seem to find any documentation on how to programatically write to a proc file. Ideally, I would like to add a timestamp with other user details every time the proc file is opened for read or for write. Again, I've found where I can add the read and write functions that are triggered when the proc file is opened, but I can't find documentation on how to actually write to a proc file programatically. This would be different from a regular IO read/write, correct?

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  • What happens when we say "listen to a port" ?

    - by smwikipedia
    Hi, When we start a server application, we always need to speicify the port number it listens to. But how is this "listening mechanism" implemented under the hood? My current imagination is like this: The operating system associate the port number with some buffer. The server application's responsibiligy is to monitor this buffer. If there's no data in this buffer, the server application's listen operation will just block the application. When some data arrives from the wire, the operating system will know that check the data and see if it is targed at this port number. And then it will fill the buffer. And then OS will notify the blocked server application and the server application will get the data and continue to run. Question is: If the above scenario is correct, how could the opearting system know there's data arriving from wire? It cannot be a busy pooling. Is it some kind of interrupt-based mechanism? If there's too much data arriving and the buffer is not big enough, will there be data loss? Is the "listen to a port" operation really a blocking operation? Many thanks.

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  • recvfrom returns invalid argument when *from* is passed

    - by Aditya Sehgal
    I am currently writing a small UDP server program in linux. The UDP server will receive packets from two different peers and will perform different operations based on from which peer it received the packet. I am trying to determine the source from where I receive the packet. However, when select returns and recvfrom is called, it returns with an error of Invalid Argument. If I pass NULL as the second last arguments, recvfrom succeeds. I have tried declaring fromAddr as struct sockaddr_storage, struct sockaddr_in, struct sockaddr without any success. Is their something wrong with this code? Is this the correct way to determine the source of the packet? The code snippet follows. ` /*TODO : update for TCP. use recv */ if((pkInfo->rcvLen=recvfrom(psInfo->sockFd, pkInfo->buffer, MAX_PKTSZ, 0, /* (struct sockaddr*)&fromAddr,*/ NULL, &(addrLen) )) < 0) { perror("RecvFrom failed\n"); } else { /*Apply Filter */ #if 0 struct sockaddr_in* tmpAddr; tmpAddr = (struct sockaddr_in* )&fromAddr; printf("Received Msg From %s\n",inet_ntoa(tmpAddr->sin_addr)); #endif printf("Packet Received of len = %d\n",pkInfo->rcvLen); } `

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  • How do you manage tasks within your work?

    - by Michael
    Just wondering how you all manage your workload effectively when there's a lot of your plate? What do you do to break it down into bite-size chunks and how do you track progress of each task? Do you find TDD helps to focus your attention of getting areas of functionality complete before moving onto the next one? I quite often find myself getting a bit overwhelmed when I have an involving task on the go (even if it can be broken down into lots of small chunks), even though I know I'm more than capable of doing the work. We have a kind of agile approach Interested to hear how everyone manages things effectively.

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  • Why is glpk-java.jar not the same across all platforms?

    - by pruefsumme
    I'm using glpk-java in one of my projects. It provides a JNI to GLPK, a free LP/MIP solver. To use it under different platforms, you need different shared libraries (libglpk.so under Linux, libglpk.dylib under Mac OS X, glpk.dll under Windows) which is fully understandable. In addition, a java library is needed: glpk-java.jar. It's created as part of the build process. I was wondering why this JAR file (which only contains .class files) is different under different platforms? I.e., I cannot use the same glpk-java.jar under Linux and Mac OS X which means that I cannot put this file under revision control.

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  • inode_operations , warning: initialization from incompatible pointer type

    - by djTeller
    Hi everyone, I'm trying to compile a simple Kernel program that read and write from a proc file. I'm trying to set permission to that file by overriding the permission fp in inode_operations struct (.permission) static int module_permission(struct inode *inode, int op, struct nameidata *foo) { . . . } static struct inode_operations Inode_Ops_4_Our_Proc_File = { .permission = module_permission, /* check for permissions */ }; Our_Proc_File->proc_iops = &Inode_Ops_4_Our_Proc_File; For some reason, when I compile this i get - warning: initialization from incompatible pointer type on the following line: .permission = module_permission, /* check for permissions */ Any idea how to solve this? Thanks!

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  • How might a C# programmer approach writing a solution in javascript?

    - by Ben McCormack
    UPDATE: Perhaps this wasn't clear from my original post, but I'm mainly interested in knowing a best practice for how to structure javascript code while building a solution, not simply learning how to use APIs (though that is certainly important). I need to add functionality to a web site and our team has decided to approach the solution using a web service that receives a call from a JSON-formatted AJAX request from within the web site. The web service has been created and works great. Now I have been tasked with writing the javascript/html side of the solution. If I were solving this problem in C#, I would create separate classes for formatting the request, handling the AJAX request/response, parsing the response, and finally inserting the response somehow into the DOM. I would build properties and methods appropriately into each class, doing my best to separate functionality and structure where appropriate. However, I have to solve this problem in javascript. Firstly, how could I approach my solution in javascript in the way I would approach it from C# as described above? Or more importantly, what's a better way to approach structuring code in javascript? Any advice or links to helpful material on the web would be greatly appreciated. NOTE: Though perhaps not immediately relevant to this question, it may be worth noting that we will be using jQuery in our solution.

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  • Replace ",**" with a linebreak using RegEx (or something else)

    - by John
    I'm getting started with RegEx and I was wondering if anyone could help me craft a statement to convert coordinates as follows: 145.00694,-37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,-37.80301,16 to 145.00694,-37.80421 145.00686,-37.80382 145.00595,-37.8035 145.00586,-37.80301 (Strip off the last comma and value and turn it into a line break.) I can't figure out how to use wildcards to do something like that. Any help would be greatly appreciated! Thanks.

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  • Which is the best pick?

    - by Daniel
    Hi, considering I have experience with Java SE: which language should I learn(and is best for that purpose) in order to build web applications some day with it? I have been contemplating PHP and Java EE. The latter does indeed seems as an obvious choice given my Java SE knowledge. But how does it fares in comparison with PHP and how good is it for the aforementioned purpose? If there is a better language for this purpose, feel free to recommend it. Thank you.

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  • Web-Application development startup advice

    - by rpr
    Dear programmers of StackOverflow, recently me and two of my friends from college started a software company. We are developing web-applications using GWT-Spring-Hibernate and other helper frameworks. In a couple of months, we managed to set up a stable back-end and produced some demo programs for CRM solutions. Our area of interest is CRM where we can combine the flexibility of our back-end with the slick looking GWT based GUIs. Unfortunately we live in a third world country (well, kind of two and a half :) and no one here gives our work enough credit, or really cares about the advantages of web-apps. We are stuck at the moment because our current clients do not want to pay that much money for just "putting their local app on the web". Since we can not find satisfying work here, we have decided to work online/international. I was wondering if you guys know a good freelance kind of sites where we can throw ourselves into the market.. Also a question from frustration, to those who are in the field or knowledgeable/interested about web based CRM, how much would you ask/pay for lets say a web app which will keep track of all the patients of a multi-branch clinic also allowing the patients to access to view their own records? Including tiered authorization, logging etc.. Many thanks in advance for your responses!

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  • get file path from svn diff file with PHP and C

    - by coderex
    hi i have a file having svn diff i wish to extract the filenames form the diff. How to write the parser for that.. Index: libs/constant.php =================================================================== --- libs/constant.php (revision 1243) +++ libs/constant.php (revision 1244) @@ -26,5 +26,5 @@ // changesss - +// test 2 ?> \ No newline at end of file Index: libs/Tools.php =================================================================== --- libs/Tools.php (revision 1243) +++ libs/Tools.php (revision 1244) @@ -34,5 +34,5 @@ // another file an change - +// test ?> \ No newline at end of file Sample output. libs/constant.php libs/Tools.php How to write parser in PHP and C.

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  • True / false evaluation doesn't work as expected in Scheme

    - by ron
    I'm trying to compare two booleans : (if (equal? #f (string->number "123b")) "not a number" "indeed a number") When I run this in the command line of DrRacket I get "not a number" , however , when I put that piece of code in my larger code , the function doesn't return that string ("not a number") , here's the code : (define (testing x y z) (define badInput "ERROR") (if (equal? #f (string->number "123b")) "not a number" "indeed a number") (display x)) And from command line : (testing "123" 1 2) displays : 123 Why ? Furthermore , how can I return a value , whenever I choose ? Here is my "real" problem : I want to do some input check to the input of the user , but the thing is , that I want to return the error message if I need , before the code is executed , because if won't - then I would run the algorithm of my code for some incorrect input : (define (convert originalNumber s_oldBase s_newBase) (define badInput "ERROR") ; Input check - if one of the inputs is not a number then return ERROR (if (equal? #f (string->number originalNumber)) badInput) (if (equal? #f (string->number s_oldBase)) badInput) (if (equal? #f (string->number s_newBase)) badInput) (define oldBase (string->number s_oldBase)) (define newBase (string->number s_newBase)) (define outDecimal (convertIntoDecimal originalNumber oldBase)) (define result "") ; holds the new number (define remainder 0) ; remainder for each iteration (define whole 0) ; the whole number after dividing (define temp 0) (do() ((= outDecimal 0)) ; stop when the decimal value reaches 0 (set! whole (quotient outDecimal newBase)) ; calc the whole number (set! temp (* whole newBase)) (set! remainder (- outDecimal temp)) ; calc the remainder (set! result (appending result remainder)) ; append the result (set! outDecimal (+ whole 0)) ; set outDecimal = whole ) ; end of do (if (> 1 0) (string->number (list->string(reverse (string->list result))))) ) ;end of method This code won't work since it uses another method that I didn't attach to the post (but it's irrelevant to the problem . Please take a look at those three IF-s ... I want to return "ERROR" if the user put some incorrect value , for example (convert "23asb4" "b5" "9") Thanks

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  • How to filter and intercept Linux packets by using net_dev_add() API?

    - by Khajavi
    I'm writing ethernet network driver for linux. I want to receive packets, edit and resend them. I know how to edit the packet in packet_interceptor function, but how can I drop incoming packets in this function?? #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/sock.h> struct packet_type my_proto; int packet_interceptor(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { // I dont want certain packets go to upper in net_devices for further processing. // How can I drop sk_buff here?! return 0; } static int hello_init( void ) { printk(KERN_INFO "Hello, world!\n"); my_proto.type = htons(ETH_P_ALL); my_proto.dev = NULL; my_proto.func = packet_interceptor; dev_add_pack(&my_proto); return 0; } static void hello_exit(void) { dev_remove_pack(&my_proto); printk(KERN_INFO "Bye, world\n"); } module_init(hello_init); module_exit(hello_exit);

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  • How to implement a list fold in Java

    - by Peter Kofler
    I have a List and want to reduce it to a single value (functional programing term "fold", Ruby term "inject"), like Arrays.asList("a", "b", "c") ... fold ... "a,b,c" As I am infected with functional programing ideas (Scala), I am looking for an easier/shorter way to code it than sb = new StringBuilder for ... { append ... } sb.toString

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  • Creating Delegates With Lambda Expressions in F#

    - by Matt H
    Why does... type IntDelegate = delegate of int -> unit type ListHelper = static member ApplyDelegate (l : int list) (d : IntDelegate) = l |> List.iter (fun x -> d.Invoke x) ListHelper.ApplyDelegate [1..10] (fun x -> printfn "%d" x) not compile, when: type IntDelegate = delegate of int -> unit type ListHelper = static member ApplyDelegate (l : int list, d : IntDelegate) = l |> List.iter (fun x -> d.Invoke x) ListHelper.ApplyDelegate ([1..10], (fun x -> printfn "%d" x)) does? The only difference that is that in the second one, ApplyDelegate takes its parameters as a tuple. Error 1 This function takes too many arguments, or is used in a context where a function is not expected

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  • Why I can't called my doSomething method?

    - by Tattat
    This is my DrawSomethingCmd: #import "Command.h"; @interface DrawSomethingCmd : Command { } -(void)doSomething; -(void)execute; @end and the DrawSomethingCmd.m's doSomething method is like that: -(void)doSomething{ NSLog(@"did"); } The Command.h: #import <Foundation/Foundation.h> @interface Command : NSObject { } -(void)execute; And the Command.m: #import "Command.h" @implementation Command -(id)init{ return self; } -(void)execute{ } @end And I have the method like this: DrawSomethingCmd *tempCmd = [[DrawSomethingCmd alloc] init]; [tempCmd doSomething]; But my Console did't show any things on that, what's going on?

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