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• Have you dealt with space hardening?

  - by Tim Post

  I am very eager to study best practices when it comes to space hardening. For instance, I've read (though I can't find the article any longer) that some core parts of the Mars rovers did not use dynamic memory allocation, in fact it was forbidden. I've also read that old fashioned core memory may be preferable in space. I was looking at some of the projects associated with the Google Lunar Challenge and wondering what it would feel like to get code on the moon, or even just into space. I know that space hardened boards offer some sanity in such a harsh environment, however I'm wondering (as a C programmer) how I would need to adjust my thinking and code if I was writing something that would run in space? I think the next few years might show more growth in private space companies, I'd really like to at least be somewhat knowledgeable regarding best practices. Can anyone recommend some books, offer links to papers on the topic or (gasp) even a simulator that shows you what happens to a program if radiation, cold or heat bombards a board that sustained damage to its insulation? I think the goal is keeping humans inside of a space craft (as far as fixing or swapping stuff) and avoiding missions to fix things. Furthermore, if the board maintains some critical system, early warnings seem paramount.

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• How to set up Nginx as a caching reverse proxy?

  - by Continuation

  I heard recently that Nginx has added caching to its reverse proxy feature. I looked around but couldn't find much info about it. I want to set up Nginx as a caching reverse proxy in front of Apache/Django: to have Nginx proxy requests for some (but not all) dynamic pages to Apache, then cache the generated pages and serve subsequent requests for those pages from cache. Ideally I'd want to invalidate cache in 2 ways: Set an expiration date on the cached item To explicitly invalidate the cached item. E.g. if my Django backend has updated certain data, I'd want to tell Nginx to invalidate the cache of the affected pages Is it possible to set Nginx to do that? How?

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• PyGTK: Manually render an existing widget at a given Rectangle? (TextView in a custom CellRenderer)

  - by NicDumZ

  Hello! I am trying to draw a TextView into the cell of a TreeView. (Why? I would like to have custom tags on text, so they can be clickable and trigger different actions/popup menus depending on where user clicks). I have been trying to write a customized CellRenderer for this purpose, but so far I failed because I find it extremely difficult to find generic documentation on rendering design in gtk. More than an answer at the specific question (that might be hard/not doable, and I'm not expecting you to do everything for me), I am first looking for documentation on how a widget is rendered, to understand how one is supposed to implement a CellRenderer. Can you share any link that explains, either for gtk or for pygtk, the rendering mechanism? More specifically: size allocation mechanism (should I say protocol?). I understand that a window has a defined size, and then queries its children, saying "my size is w x h, what would be your ideal size, buddy?", and then sometimes shrinks children when all children cant fit together at their ideal sizes. Any specific documentation on that, and on particular on when this happens during rendering? How are rendered "builtin" widgets? What kind of methods do they call on Widget base class? On the parent Window? When? Do they use pango.Layout? can you manually draw a TextView onto a pango.Layout object? This link gives an interesting example showing how you can draw content in a pango.Layout object and use it in a CellRenderer. I guess that I could adapt it if only I understood how TextView widget are rendered. Or perhaps, to put it more simply: given an existing widget instance, how does one render it at a specific gdk.Rectangle? Thanks a lot.

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• Tracking my home IP from anywhere on the internet?

  - by oKtosiTe

  I have an ISP that serves semi-permanent IPv4 addresses. They can't promise fixed IP addresses, but unexpected changes are quite rare. This begs me to ask however: what would be the easiest/most reliable way to track my home IP address so I can access my (Windows 7) home server even in the case of an address change? Please note: for reasons that I don't want to go in to, I'd like to avoid using any "dynamic DNS" type services. Instead I'd prefer some way to perhaps have the home server leave an occasional/triggered "address stamp" on a remote, off-site server (by SSH, HTTP post or similar, preferably over an encrypted connection).

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• Choosing a monitoring system for a dynamically scaling environment: Nagios v. Zabbix

  - by wickett

  When operating in the cloud and scaling boxes automatically, there are certain monitoring issues that one experiences. Sometimes we might be monitoring 10 boxes and sometimes 100. The machines will scale up and down based on a demand. Right now, I think the best solution to this is to choose a monitoring solution that will instantiation of targets via calls to an API. But, is this really the best? I like the idea of dynamic discovery, but that is also a problem in the cloud seeing that the targets are not all in the same subnet. What monitoring solutions allow for a scaling environment like this? Zabbix currently has a draft API but I have been unable to fund a similar API for Nagios. Is there a similar API for Nagios? Anyone have any alternate suggestions besides Nagios and Zabbix?

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• Which TCP ports to use?

  - by rowatt

  Is there a TCP port range which I can be sure will not be used by anything else for traffic between two machines? If I am reading RFC6335 correctly, I can be sure that no other applications will use specific ports in the Dynamic/Private/Ephemeral range of 49152-65535. However, if I understand correctly, it also states (section 8.1.2) that an application shouldn't assume that any given port in that range is available at any given time, which would mean I can't be 100% sure that it will be unused all the time. Specifically, I want to assign specific SSH traffic to a different port for the security benefit and so I can classify it differently for QoS purposes, and not have to worry about changing the port in the future.

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• nginx not returning 304 on cached content

  - by Don H

  I'm using nginx as a reverse proxy with an Apache back-end handling some PHP files. The files return the right expiry headers and proxy_cache does a good job of caching them, but I've noticed that the cached content returns a 200 on every refresh, when it might be more efficient to return a 304 on the cached files. The files in question are generated by PHP. The urls do not have .php in them as they've been prettified. Any idea why nginx might not be returning 304 on repeated visits to a cached PHP output? To clarify: It's using proxy_cache for caching dynamic PHP pages (not static html pages generated by PHP). I'm setting expires headers in the PHP file of time + 24 hours. With that in mind, I was hoping nginx would be able to then return 304s on its cached versions during that 24 hour window.

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• Get OpenVPN clients names to resolve through dnsmasq

  - by Fake Name

  I have a PFSense box running as an OpenVPN server. There are several remote devices that connect through the VPN (as tap devices). The VPN stuff is working, I can access the remote hardware by looking up the IP assigned to each device on the PFSense router. What I'd like is to have it so I can resolve the remote hardware addresses via DNS while on the local network. Note that this is only local-network - remote-device (they're backup boxes). I don't need to have the remote devices resolve using the local DNS forwarding agent. I have the rest of the devices on the network that need to be accessible via DNS report their name during the DHCP process. However, the IP assignment for OpenVPN tap clients, while it is dynamic (which is why I need DNS), does not seem to use the local DHCP server. How can I have my openvpn server add information for it's clients to the dnsmask resolver? Is this setup even reasonable (I'm not familiar with openVPN at all)?

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• how to obtain the relative path of a resource in a j2ee project

  - by Neeraj

  I have a Dynamic Web Project having a flat file (or say text file). I have created a servlet in which I need to use this file. My code is as following: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // String resource = request.getParameter ("json") ; if ( resource != null && !resource.equals ( "" ) ) { //use getResourceAsStream ( ) to properly get the file. InputStream is = getServletContext ().getResourceAsStream ("rateJSON") ; if ( is != null ) { // the resource exists response.setContentType("application/json"); response.setHeader("Pragma", "No-cache"); response.setDateHeader("Expires", 0); response.setHeader("Cache-Control", "no-cache"); StringWriter sw = new StringWriter ( ) ; for ( int c = is.read ( ) ; c != -1; c = is.read ( ) ) { sw.write ( c ) ; } PrintWriter out = response.getWriter(); out.print (sw.toString ()) ; out.flush(); } } } The problem is that the InputStream is has null value. I'm not sure how to get the correct relative path. I'm using JBOSS as the app server. I have added the resource file in the WebContent directory of a Dynamic Web Project. As a different approch, I tried this: protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub ServletConfig config = getServletConfig(); String contextName = config.getInitParameter("ApplicationName"); System.out.println("context name"+ contextName); String contextPath = config.getServletContext().getRealPath(contextName); System.out.println("context Path"+contextPath); //contextPath = contextPath.substring(0, contextPath.indexOf(contextName)); contextPath += "\\rateJSON.txt"; System.out.println(contextPath); String resource = request.getParameter ("json") ; System.out.println("Hi there1"+resource); if ( resource != null && !resource.equals ( "" ) ) { System.out.println("Hi there"); //use getResourceAsStream ( ) to properly get the file. //InputStream is = getServletContext ().getResourceAsStream (resource) ; InputStream is = getServletConfig().getServletContext().getResourceAsStream(contextPath); if ( is != null ) { // the resource exists System.out.println("Hi there2"); response.setContentType("application/json"); response.setHeader("Pragma", "No-cache"); response.setDateHeader("Expires", 0); response.setHeader("Cache-Control", "no-cache"); StringWriter sw = new StringWriter ( ); for ( int c = is.read ( ) ; c != -1; c = is.read ( ) ) { sw.write ( c ) ; System.out.println(c); } PrintWriter out = response.getWriter(); out.print (sw.toString ()) ; System.out.println(sw.toString()); out.flush(); } } } The value of contextPath is now: C:\JBOSS\jboss-5.0.1.GA\server\default\tmp\4p72206b-uo5r7k-g0vn9pof-1-g0vsh0o9-b7\Nationwide.war\WEB-INF\rateJSON But at this location the rateJSON file is not there? It seems JBOSS is not putting this file in the App.war or doesn't deploy it??? Could someone please help me?

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• How to suspend and resume browser tab groups?

  - by Robin Green

  Modern browsers such as Firefox and Chrome are able to shutdown and restore the same group of tabs they had before the next time you open them, and even sometimes remember additional tab state such as scroll position within the tab. I would like ideally to be able to select a group of tabs (about some coherent theme, perhaps) and save them away into some kind of "folder" that I could later open independently, without opening any other tabs. Obviously I can use bookmarks for this, but bookmarks are kind of old-fashioned. It would be excellent if it could also record forms that I had filled in but not submitted, scroll position, tab position within the tab group, and any other "dynamic" aspects of the current tab state.

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• How to efficiently resize an array of values, without boxing, used within a Dictionary<string, float[]>

  - by makerofthings7

  In the code below, Pages is defined as public SortedDictionary<DateTime, float[]> Pages { get; set; } I am trying to dynamically increase the size of this array. Can anyone tell how to increase the sized of the innermost float[]? var tt = currentContainer.Pages[dateTime]; Array.Resize<float>(ref tt, currentContainer.Pages.Count + 1); Fail 1 I tried the following code and get index out of range exception SortedDictionary<DateTime, float[]> Pages = new SortedDictionary<DateTime,float[]>(); float[] xx = new float[1]; xx[0] = 1; DateTime tempTime = DateTime.UtcNow; Pages.Add(tempTime, xx); var tt = Pages[tempTime]; Array.Resize<float>(ref tt, Pages.Count + 1); Pages[tempTime][1] = 2; Fail 2 The following gives a compile time error (property, index, or dynamic member can't be used as a ref value) SortedDictionary<DateTime, float[]> Pages = new SortedDictionary<DateTime,float[]>(); float[] xx = new float[1]; xx[0] = 1; DateTime tempTime = DateTime.UtcNow; Pages.Add(tempTime, xx); var tt = Pages[tempTime]; // The line below is different from Fail 1 above ... compile time error Array.Resize<float>(ref Pages[tempTime], Pages.Count + 1); Pages[tempTime][1] = 2; Question What is the most performant answer to resize this array? Would the answer change if it's likely that the final size will be 100-200 floats or 700-900 floats? What if I change my allocation size from +1 to +128? .. or larger?

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• What protocols will/are ISPs use for IPv6 deployment?

  - by rbeede

  Currently ISPs deal out addresses via DHCP for IPv4 dynamic (single) addresses. What protocol will/are ISPs going to use for IPv6 when they can hand a customer an entire /64 (or /48 if they are nice) block? DHCPv6, RA? For ISPs that support true end-to-end IPv6 will they provide gateway devices (similar to cable modem or true DSL bridges for example) that receive border information for that specific customer? I'm just trying to get an idea of how your common residential service customer will have to configure things in an IPv6 Internet (whenever that comes). Will it be something customers are expected to statically configure on their home wireless router? Today with IPv4 I do it like this: Modem (bridge) passes public IPv4 obtained via DHCPv4 from ISP to second device (wireless router). It in turn has its own DHCPv4 service it provides on the internal lan.

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• Why no Win16 support in 64-bit Windows?

  - by dsimcha

  My understanding (from Wikipedia) is that the x64 instruction set supports executing 16-bit protected mode code from long mode, but cannot execute real mode code without being switched out of long mode because long mode lacks virtual 8086 mode. Therefore, it stands to reason that real mode DOS apps can't be run in Win64 w/o software emulation or dynamic translation. However, why was support for Win16 protected-mode apps excluded when support for them seems (at least at first glance) to be reasonably implementable and is included in newer versions of Win32? Was it just a matter of demand not being high enough to justify implementation costs (and the win32 version was already implemented), or is there a good technical reason?

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• What is the best file system to use for a second hard drive when dual booting between WinXP and Win7

  - by Corey

  I am dual booting for legacy reasons, and I have a 2nd internal drive that I would like to use from both XP and 7. Should I go with the standard NTFS? (will the secuirty features be an issue, with different SIDs from the different users) Should I go with FAT32? Should I try out the new exFAT? Also, I curently have two of my 3 drives as "dynamic disks" and 1 spaned volume created on them. (i did this from XP) Win7 can see them/it fine. Is this an ok thing to do?

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• What is the best file system to use for a second hard drive when dual booting between WinXP and Win7

  - by Corey

  What is the best file system to use for a second hard drive when dual booting between WinXP and Win7? I am dual booting for legacy reasons, and I have a 2nd internal drive that I would like to use from both XP and 7. Should I go with the standard NTFS? (will the secuirty features be an issue, with different SIDs from the different users) Should I go with FAT32? Should I try out the new exFAT? Also, I curently have two of my 3 drives as "dynamic disks" and 1 spaned volume created on them. (i did this from XP) Win7 can see them/it fine. Is this an ok thing to do?

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• How string accepting interface should look like?

  - by ybungalobill

  Hello, This is a follow up of this question. Suppose I write a C++ interface that accepts or returns a const string. I can use a const char* zero-terminated string: void f(const char* str); // (1) The other way would be to use an std::string: void f(const string& str); // (2) It's also possible to write an overload and accept both: void f(const char* str); // (3) void f(const string& str); Or even a template in conjunction with boost string algorithms: template<class Range> void f(const Range& str); // (4) My thoughts are: (1) is not C++ish and may be less efficient when subsequent operations may need to know the string length. (2) is bad because now f("long very long C string"); invokes a construction of std::string which involves a heap allocation. If f uses that string just to pass it to some low-level interface that expects a C-string (like fopen) then it is just a waste of resources. (3) causes code duplication. Although one f can call the other depending on what is the most efficient implementation. However we can't overload based on return type, like in case of std::exception::what() that returns a const char*. (4) doesn't work with separate compilation and may cause even larger code bloat. Choosing between (1) and (2) based on what's needed by the implementation is, well, leaking an implementation detail to the interface. The question is: what is the preffered way? Is there any single guideline I can follow? What's your experience?

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• I have a 21TB array but only 16TB is visible from Windows

  - by Relentim

  CONTROLLER Raid Controller: 3Ware 9650SE-24M8 Disks: 21 x 1TB RAID5 Stripe 64KB WINDOWS OS: Windows Server 2003 SP2 32x Disk: Dynamic 19557.44GB Volume: Capacity 15832.19GB I guess my array must have a 4KB block size which is limiting it to 16TB. I think I would have to switch to a 64KB block size to be able to see a maximum of 256TB. Or create another unit on my controller to go above 16TB of storage. Unfortunately I have already added over 16TB, ideally I would like to shrink the array and reclaim the 5 disks that aren't doing anything. I don't think this is possible. More likely, can I change the block size so 20TB becomes visible in windows?

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• Problem using delete[] (Heap corruption) when implementing operator+= (C++)

  - by Darel

  I've been trying to figure this out for hours now, and I'm at my wit's end. I would surely appreciate it if someone could tell me when I'm doing wrong. I have written a simple class to emulate basic functionality of strings. The class's members include a character pointer data (which points to a dynamically created char array) and an integer strSize (which holds the length of the string, sans terminator.) Since I'm using new and delete, I've implemented the copy constructor and destructor. My problem occurs when I try to implement the operator+=. The LHS object builds the new string correctly - I can even print it using cout - but the problem comes when I try to deallocate the data pointer in the destructor: I get a "Heap Corruption Detected after normal block" at the memory address pointed to by the data array the destructor is trying to deallocate. Here's my complete class and test program: #include <iostream> using namespace std; // Class to emulate string class Str { public: // Default constructor Str(): data(0), strSize(0) { } // Constructor from string literal Str(const char* cp) { data = new char[strlen(cp) + 1]; char *p = data; const char* q = cp; while (*q) *p++ = *q++; *p = '\0'; strSize = strlen(cp); } Str& operator+=(const Str& rhs) { // create new dynamic memory to hold concatenated string char* str = new char[strSize + rhs.strSize + 1]; char* p = str; // new data char* i = data; // old data const char* q = rhs.data; // data to append // append old string to new string in new dynamic memory while (*p++ = *i++) ; p--; while (*p++ = *q++) ; *p = '\0'; // assign new values to data and strSize delete[] data; data = str; strSize += rhs.strSize; return *this; } // Copy constructor Str(const Str& s) { data = new char[s.strSize + 1]; char *p = data; char *q = s.data; while (*q) *p++ = *q++; *p = '\0'; strSize = s.strSize; } // destructor ~Str() { delete[] data; } const char& operator[](int i) const { return data[i]; } int size() const { return strSize; } private: char *data; int strSize; }; ostream& operator<<(ostream& os, const Str& s) { for (int i = 0; i != s.size(); ++i) os << s[i]; return os; } // Test constructor, copy constructor, and += operator int main() { Str s = "hello"; // destructor for s works ok Str x = s; // destructor for x works ok s += "world!"; // destructor for s gives error cout << s << endl; cout << x << endl; return 0; }

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• Freeing of allocated memory in Solaris/Linux

  - by user355159

  Hi, I have written a small program and compiled it under Solaris/Linux platform to measure the performance of applying this code to my application. The program is written in such a way, initially using sbrk(0) system call, i have taken base address of the heap region. After that i have allocated an 1.5GB of memory using malloc system call, Then i used memcpy system call to copy 1.5GB of content to the allocated memory area. Then, I freed the allocated memory. After freeing, i used again sbrk(0) system call to view the heap size. This is where i little confused. In solaris, eventhough, i freed the memory allocated (of nearly 1.5GB) the heap size of the process is huge. But i run the same application in linux, after freeing, i found that the heap size of the process is equal to the size of the heap memory before allocation of 1.5GB. I know Solaris does not frees memory immediately, but i don't know how to tune the solaris kernel to immediately free the memory after free() system call. Also, please explain why the same problem does not comes under Linux? Can anyone help me out of this? Thanks, Santhosh.

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• Turn on PC power remotely through the Internet?

  - by W.N.

  I use SVN for my work at home and office, but I usually forget to commit the changes before shutdown. Therefore, I wish I could turn on my home/office PC at office/home. I already have TeamViewer installed on both PCs, so it will be okay as soon as the power is turned on. I have read many articles about this, I found both my PC and office computers support Wake-on-LAN. However, I don't know much about other config. And I need to turn on my computers through the Internet, not on LAN. My office Internet connection has static IP, however, my home Internet connection has dynamic IP, it changes as soon as I reset the modem, but it is not a big problem, I rarely turn the Internet modem off. And I don't have privilege to config office Internet connection, but I have Administration privilege on both PCs. Please give me details steps to turn on my office PC from home, and turn on my home PC from office.

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• Apache+FastCGI Timeout Error: "has failed to remain running for 30 seconds given 3 attempts, its restart interval has been backed off to 600 seconds"

  - by Sadjad Fouladi

  I've recently installed mod_fastcgi and Apache 2.2. I have a simple cgi script as below (test.fcgi): #!/bin/sh echo sadjad But when I invoke 'mysite.com/test.fcgi' I see "Internal Server Error" after a short period of time. The error.log file shows this error message: [Tue Jan 31 22:23:57 2006] [warn] FastCGI: (dynamic) server "~/public_html/oaduluth/dispatch.fcgi" has failed to remain running for 30 seconds given 3 attempts, its restart interval has been backed off to 600 seconds This is my .htaccess file: AddHandler fastcgi-script .fcgi RewriteEngine On RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ django.fcgi/$1 [QSA,L] What could the problem be? Is it my .htaccess file?

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• How setup federated SQL data to display limited information to a Web server in the DMZ?

  - by Pcav

  I have a SQL server behind a firewall. I need to push some limited SQL 2005 information to a Web Server in the DMZ so that I do not have to let database queries come all the way into the database server on our internal network. I want to push a small amount of dynamic data to a Web server in the DMZ and lock it down so that our hosted website does not need to come into the internal network for information; I want to put a server in the DMZ that will be the only connection allowed to the SQL database. This DMZ server will be the only server that can have any sort of connection to the back-end database so the hosting provider just pull the data from our server in the DMZ...

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• Set generic iptables rules?

  - by tftd

  This may be a really dumb question but how can you open a port on multiple interfaces without defining the interfaces? For example how do I open port 22 on all interfaces? On my machine I have some interfaces that are dynamic and may or may not be available so I have to set "generic" rules. This code is not working for me but I can't figure out why: # My default policy is to drop the input. # The other policies are required like that. $IPTABLES -P INPUT DROP $IPTABLES -P OUTPUT ACCEPT $IPTABLES -P FORWARD ACCEPT $IPTABLES -t nat -P POSTROUTING ACCEPT $IPTABLES -t nat -P PREROUTING ACCEPT $IPTABLES -t mangle -P OUTPUT ACCEPT $IPTABLES -t mangle -P PREROUTING ACCEPT #Open port 22 on all interfaces ? $IPTABLES -A INPUT -p tcp --dport 22 -j ACCEPT So apparently there's something wrong with the last line... but I can't see it?

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• segmentation fault when using pointer to pointer

  - by user3697730

  I had been trying to use a pointer to pointer in a function,but is seems that I am not doing the memory allocation correctly... My code is: #include<stdio.h> #include<math.h> #include<ctype.h> #include<stdlib.h> #include<string.h> struct list{ int data; struct list *next; }; void abc (struct list **l,struct list **l2) { *l2=NULL; l2=(struct list**)malloc( sizeof(struct list*)); (*l)->data=12; printf("%d",(*l)->data); (*l2)->next=*l2; } int main() { struct list *l,*l2; abc(&l,&l2); system("pause"); return(0); } This code compiles,but I cannot run thw program..I get a segmentation fault..What should I do?Any help would be appreciated!

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• Understanding REST through an example

  - by grifaton

  My only real exposure to the ideas of REST has been through Ruby on Rails' RESTful routing. This has suited me well for the kind of CRUD-based applications I have built with Rails, but consequently my understanding of RESTfulness is somewhat limited. Let's say we have a finite collection of Items, each of which has a unique ID, and a number of properties, such as colour, shape, and size (which might be undefined for some Items). Items can be used by a client for a period of time, but each Item can only be used by one client at once. Access to Items is regulated by a server. Clients can request the temporary use of certain items from a server. Usually, clients will only be interested in getting access to a number of Items with particular properties, rather than getting access to specific Items. When a client requests use of a number of Items, the server responds with a list of IDs corresponding to the request, or with a response that says that the requested Items are not currently available or do not exist. A client can make the following kinds of request: Tell me how many green triangle Items there are (in total/available). Give me use of 200 large red Items. I have finished with Items 21, 23, 23. Add 100 new red square Items. Delete 50 small green Items. Modify all big yellow pentagon Items to be blue. The toy example above is like a resource allocation problem I have had to deal with recently. How should I go about thinking about it RESTfully?

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