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  • Communication between parent and child

    - by Pierre
    Hi every one ! I have a little problem. I have to code a simple C application that creat a process and his child (fork()) and I have to do an operation. Parent initialize the values and child calculate. I write this : #include #include #include #include #include typedef struct { int op1; char op; int op2; }Operation; Operation *varOP; void finalResult() { float result = 0; if(varOP-op == '+') result = (varOP-op1 + varOP-op2); if(varOP-op == '-') result = (varOP-op1 - varOP-op2); if(varOP-op == '*') result = (varOP-op1 * varOP-op2); if(varOP-op == '+') result = (varOP-op1 / varOP-op2); printf("%f",result); } int main () { int p; varOP = (Operation *)malloc(sizeof(Operation)); p = fork(); if(p == 0) // If child { signal(SIGUSR1, finalResult ); pause(); } if(p 0) // If parent { varOP-op = '+'; varOP-op1 = 2; varOP-op2 = 3; kill(p, SIGUSR1); wait(NULL); } return 0; } But my child is never called. Is there something wrong with my code? Thanks for your help !

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  • Segmentation in Linux : Segmentation & Paging are redundant?

    - by claws
    Hello, I'm reading "Understanding Linux Kernel". This is the snippet that explains how Linux uses Segmentation which I didn't understand. Segmentation has been included in 80 x 86 microprocessors to encourage programmers to split their applications into logically related entities, such as subroutines or global and local data areas. However, Linux uses segmentation in a very limited way. In fact, segmentation and paging are somewhat redundant, because both can be used to separate the physical address spaces of processes: segmentation can assign a different linear address space to each process, while paging can map the same linear address space into different physical address spaces. Linux prefers paging to segmentation for the following reasons: Memory management is simpler when all processes use the same segment register values that is, when they share the same set of linear addresses. One of the design objectives of Linux is portability to a wide range of architectures; RISC architectures in particular have limited support for segmentation. All Linux processes running in User Mode use the same pair of segments to address instructions and data. These segments are called user code segment and user data segment , respectively. Similarly, all Linux processes running in Kernel Mode use the same pair of segments to address instructions and data: they are called kernel code segment and kernel data segment , respectively. Table 2-3 shows the values of the Segment Descriptor fields for these four crucial segments. I'm unable to understand 1st and last paragraph.

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  • delete a file in protected mode env(like windows xp)

    - by JGC
    hi I write a program to delete a file from somewhere of my harddisk in 8086 but when i use int 21h (ah=41h) an error happens and carry set to 1.and I cannot delete that. does anyone know what can I do? I think it should be from protected mode which does not allow my program to delete another file.I want the answer and language is not matter.

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  • How to manipulate *huge* amounts of data

    - by Alejandro
    Hi there! I'm having the following problem. I need to store huge amounts of information (~32 GB) and be able to manipulate it as fast as possible. I'm wondering what's the best way to do it (combinations of programming language + OS + whatever you think its important). The structure of the information I'm using is a 4D array (NxNxNxN) of double-precission floats (8 bytes). Right now my solution is to slice the 4D array into 2D arrays and store them in separate files in the HDD of my computer. This is really slow and the manipulation of the data is unbearable, so this is no solution at all! I'm thinking on moving into a Supercomputing facility in my country and store all the information in the RAM, but I'm not sure how to implement an application to take advantage of it (I'm not a professional programmer, so any book/reference will help me a lot). An alternative solution I'm thinking on is to buy a dedicated server with lots of RAM, but I don't know for sure if that will solve the problem. So right now my ignorance doesn't let me choose the best way to proceed. What would you do if you were in this situation? I'm open to any idea. Thanks in advance!

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  • Counting HTML images with Python

    - by user2537246
    I need some feedback on how to count HTML images with Python 3.01 after extracting them, maybe my regular expression are used properly. Here is my code: import re, os import urllib.request def get_image(url): url = 'http://www.google.com' total = 0 try: f = urllib.request.urlopen(url) for line in f.readline(): line = re.compile('<img.*?src="(.*?)">') if total > 0: x = line.count(total) total += x print('Images total:', total) except: pass

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  • Are there any GOOD Chef, Chef-Server and Chef-Client tutorials out there?

    - by btelles
    Hi there, Chef from Opscode seems to be really useful for configuring servers and such, but trying to follow their documentation is a little difficult. Some terms are defined after they are used, and definitions sometimes reference new terms that you haven't yet encountered. Anyone know of any GOOD tutorials/walk-throughs for getting a good understanding of Chef, Chef-Server and Chef-Client? I remember seeing one video presentation online, but it barely scratched the surface.

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  • we would like the user to be able to pick a file from native file system and drag & drop it to our a

    - by user261740
    We have an existing java desktop application which starts, when user click on our application icon (placed on desktop) OR double click on executable(.exe). It opens the frame which allows user to select the file from native file system and uploads it to the server. Now we would like to facilitate user, that he can pick a file from windows explorer and drag it to the "shortcut / Application icon" & drop it on the "shortcut / Application icon" on the desktop. This would start the uploading of that file on the server. we need to capture the action of "drop" and launch on shortcut.. which may be completely not related to java, it can be very generic to any application. We are using JSmooth to build an executable from jar and NSIS for installer purpose. I would like to know.. How we can launch the application if user drops local file onto the system icon ? How we get the absolute path of file name which has been dropped onto the executable ?

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  • maximum memory which malloc can allocate!

    - by Vikas
    I was trying to figure out how much memory I can malloc to maximum extent on my machine (1 Gb RAM 160 Gb HD Windows platform). I read that maximum memory malloc can allocate is limited to physical memory.(on heap) Also when a program exceeds consumption of memory to a certain level, the computer stops working because other applications do not get enough memory that they require. So to confirm,I wrote a small program in C, int main(){ int *p; while(1){ p=(int *)malloc(4); if(!p)break; } } Hoping that there would be a time when memory allocation will fail and loop will be breaked. But my computer hanged as It was an infinite loop. I waited for about an hour and finally I had to forcely shut down my computer. Some questions: Does malloc allocate memory from HD also? What was the reason for above behaviour? Why didn't loop breaked at any point of time.? Why wasn't there any allocation failure?

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  • Can the adp2 device be flashed with 2.0?

    - by Rick Rodriguez
    Simple question...can the adp2 that I just bought through the Android Market be flashed with Android 2.0? I can't find anything anywhere. The HTC developer support only has system images for the adp1 and adp2 phones up to 1.6. If it can't I will be sending the phone back for a full refund. Thanks.

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  • Installing Windows XP with pre installed Windows 7

    - by user243680
    Hello! I want to install Windows XP on my dell laptop which has pre installed Windows7 on it. I want windows Xp on my system because of my project issue. Now the problem is Windows7 does not allow to install Windows Xp on my system. I dont mind if windows 7 gets replaced by Windows XP,all i want is windows XP on my system.I am not getting the way to install XP. Can anyone guide me how to install Windows XP on my laptop? i need an urgent help.

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