January 2004 - openSUSE Programming - openSUSE Mailing Lists

WAS "A good book on C programming", now an APPOLOGY
by Gavin Henry 04 Mar '04

04 Mar '04

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Dear Everyone, I was had this pointed out to me, by Simon Perreault <nomis80(a)nomis80.org> (with my reply): "On Saturday 27 Dec 2003 8:49 pm, you wrote: > 1) Please do not cross-post. (This means sending the same message to many > lists.) OK, guilty, but I wanted a varied response, as different people subscribe to different lists. > > 2) Please stay on topic. This has nothing to do with Fedora. Fedora is GNU/Linux, there are C programmers, like you that use Fedora, and it is a general discussion list. What's the problem? I'm not asking for money for for you to join some crazy scheme. This kind of attitude annoys me about GNU/Linux, I am not wasting anyones time, so I don't see what the problem is." And his last reply: "On December 27, 2003 16:11, you wrote: > This kind of attitude annoys me about GNU/Linux, I am not wasting anyones > time, so I don't see what the problem is. Yes, you are wasting time (and bandwidth, as there are some people on very slow connections) when you are not on topic. This list is not even about GNU/Linux, it is about Fedora. General Linux questions do not belong here. This is Fedora-related stuff only. There are tons of Linux and C mailing lists. This is a quick lesson (that everyone must learn, I did too) on netiquette. You should Google a bit on that topic, particularly on stuff related to mailing lists." I am sorry if I have wasted everyones time and bandwidth, but I have spent the last 3 days searching for up to date links and book reviews, some things you never find, like the website: http://www.accu.org/bookreviews/public/ recommended by another user. I admit, I have cross posted, as I not only use Fedora, but Debian, SUSE and Gentoo. These are all different distro's with different user bases. I wanted to get a good feel of what are good texts from all the C programmers out their. I didn't get a response like above from anyone else. Even Alan Cox replied to me. What I don't understand is, and I quote, "This list is not even about GNU/Linux, it is about Fedora." What is Fedora then? Again, sorry to waste everyones time, but you have all helped me out. - -- Regards http://www.magicfx.co.uk http://www.suretecsystems.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (GNU/Linux) iD8DBQE/7f0YgNqd7Kng8UoRAimuAKCikZFb2yBGtrHss8AWHmb7pPwQMwCg4OAT hiT3sr0rPLJBLtQl/uiqQOU= =mTvq -----END PGP SIGNATURE-----

8 11

A hidden race condition in basic pthread program?
by praisetazio 30 Jan '04

30 Jan '04

The following code should simulate a port with M places and N ships accessing to it. The problem: in the "entering_request" function, the program controls how many ships are in port, if there are too many ships the program should block on a condition variable. The problem is that it does not work, and I usually get more than M ships at runtime. I think that I am misunderstanding something, anybody could enlighten me? #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #define N 10 #define M 5 struct port { pthread_mutex_t mutex; pthread_cond_t full; int ships; int waiting; } Port = { PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER, 0, 0 }; void* ship (void* arg); int main() { void* nothing; pthread_t ships[N]; int i; pthread_setconcurrency(N); for (i=0; i<N; i++) pthread_create (&ships[i], NULL, ship, NULL); for (i=0; i<N; i++) pthread_join (ships[i], &nothing); printf("The end\n"); return 0; } void entering_request() { pthread_mutex_lock(&Port.mutex); if (Port.ships>=M) { Port.waiting++; printf("ship %d blocked\n", pthread_self()); pthread_cond_wait(&Port.full, &Port.mutex); printf("ship %d unblocked\n", pthread_self()); Port.waiting--; } } void entering() { printf ("ship %d enters the port", pthread_self()); printf ("\n%d ships in port\n", Port.ships); } void leaving_entrance() { Port.ships++; printf("Ships inside the port: %d\n", Port.ships); pthread_mutex_unlock(&Port.mutex); } void stationing () { int l, i; srand(time(NULL)); printf("La ship %d is inside with other %d ships.\n", pthread_self(), Port.ships); l = rand(); /* Wasting time */ for (i=0; i<l; i++); } void exit_request() { pthread_mutex_lock(&Port.mutex); } void exiting() { printf ("ship %d out of the port\n", pthread_self()); printf ("%d ships\n remain in port", Port.ships); } void leaving_exit() { Port.ships--; if (Port.waiting) pthread_cond_signal (&Port.full); pthread_mutex_unlock(&Port.mutex); } void* ship (void* arg) { int i; for (i=0; i<3000; i++) { entering_request(); entering(); leaving_entrance(); stationing(); exit_request(); exiting(); leaving_exit(); } return NULL; }

3 5

Thread sleep
by Lukacs Zsolt 27 Jan '04

27 Jan '04

Hi, I have created a process which cretes some threads. I would like to sleep one thread (let's say for 500 ms) while the other threads are still working. Does anybody know how to do that? I have already tried to use the sleep() function but it seems that it the whole process goes to sleep not just olny one of the threads owned by the process. Thanks Zsolt

4 4

relocation error: undefined symbol glDeleteProgramARB
by Indra Geys 25 Jan '04

25 Jan '04

Hello, I am just changed from redhat 9.0 to suse and I have some problems with my code. I managed to solve some compile errors already but if I now start up my program, then I get some error: relocation error: undefined symbol: glDeleteProgramARB and it crashes. This glDeleteProgramARB is certainly in defined in the header gtkglext and it is also in the lib which is in my path (compilation and linking gives no problem) Does somebody knows what causes this problem, and more important: how can I solve it? Thanks, Indra

2 1

Supercomputers and Linux s/w
by Maura Edelweiss Monville 25 Jan '04

25 Jan '04

I'm runnig many simulations with one only different paramater value. The reason is to generate statistical data. I have an account on the super-computer center shown in the following web page: http://harpo.wustl.edu/hardware.html There seems to be a Linux system (SGI Altix) but because of the way my account was set up my entry is on Harpo which runs Irix. I'll be runnin on batch so I do not know if this is important at all. I'd like to be able to recompile and run my simulation (developed on SuSE) with the least possible discomfort from s/w environment incompatibilities ... There is no GNU Scientific Library which I need. My question for you is: What should I ask this center administrator for ? They are amenable to install some s/w upon user request ... In the case GSL cannot run/be installed then is ther any replacement for a good Random Number Generator that you'd advice ? I like SuSE and am very gratefull to all generous people that have been helping me regularly. The only drawback is when it comes to porting my project to some other platform ... Thank you in advance for your help. maura Thank you for clarifying my ideas. Maura

3 2

Suse and LVM VFS-lock patch
by Rajesh Saxena 20 Jan '04

20 Jan '04

Greetings list............ after posting to the linux-lvm mailing list I am informed that there is a patch[1] for LVM which allows more reliable filesystem snapshots. The last patch for the 2.4 kernel [2] seems to be for 2.4.20 but Suse running 2.4.21 instead. Question to Suse developers or experienced kernel programmer: Do the default kernel have this patch included? [1] http://marc.theaimsgroup.com/?l=linux-lvm&m=107426158117112&w=2 [2] http://tech.sistina.com/cgi-bin/viewcvs.cgi/LVM/PATCHES/ ______________________________________________________________________ Post your free ad now! http://personals.yahoo.ca

1 0

libpthread.so.0 not found trying to link simple app. Library is present in /lib
by Burt Bicksler 19 Jan '04

19 Jan '04

Hi, I’m trying to build a simple hello world test application using pthreads. This is on a stock SUSE Pro 8.2 installation with all of the latest patches installed. During the link the linker whines that it cannot find libpthread.so.0. I have tried presenting this as -l/lib/libpthread.so.0 (which is where the lib physically resides). This doesn’t change the problem, still no joy with linking the application. I’m probably doing something wrong, but I’ve scanned the web with Google and, while I’ve found similar problems with other libraries mentioned all of those appear to be related to not having the library installed. I haven’t been able to track down a good specific example showing what library to link with, so I’m making the assumption that libpthread.so.0 is the correct one, but it doesn’t appear to be recognized by the linker. Has anyone else encountered this problem, and if so what was the solution? If you can point me to a specific document that details the settings to use to build a “hello world” threaded application on SUSE 8.2 that would be great. Thanks, Burt --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.558 / Virus Database: 350 - Release Date: 1/2/2004

2 1

newer Kdevelop and dependencies on KDE 3.2
by Ivan Sergio Borgonovo 19 Jan '04

19 Jan '04

Anyone made Kdevelop 3 packages for 9.0 without making them dependent on KDElibs for KDE 3.2? I'm trying to make the package right now but compiling it is pretty long even on an Athlon 2500+ 1Gb RAM. Correcting mistakes in the spec file is pretty expensive.

1 0

glade prob
by oguz eren 19 Jan '04

19 Jan '04

Hi, I'm trying to learn glade. autogen.sh failed on my first try; giving the error below: ./configure: line 4068: syntax error near unexpected token `PACKAGE,' ./configure: line 4068: `PKG_CHECK_MODULES(PACKAGE, $pkg_modules)' Then i learned that i had to install pkgconfig; i did so; but this time autogen gave the following error: checking for gtk+-2.0 >= 2.0.0... Package gtk+-2.0 was not found in the pkg-config search path. Perhaps you should add the directory containing `gtk+-2.0.pc' to the PKG_CONFIG_PATH environment variable No package 'gtk+-2.0' found configure: error: Library requirements (gtk+-2.0 >= 2.0.0) not met; consider adjusting the PKG_CONFIG_PATH environment variable if your libraries are in a nonstandard prefix so pkg-config can find them. How do i have to set PKG_CONFIG_PATH environment variable? Thanks in advance.

2 2

RE: [suse-programming-e] Set uid on executables
by Hallingstad Håkon 19 Jan '04

19 Jan '04

Try to write /usr/bin/passwd without setuid/setgid. I thought the hole point with the shebang-scheme was that we could write scripts so that they would seem to work excatly as compiled programs. The kernel does not make the system more safe by ignoring setuid/setgid on scripts, since I can always write a setuid/setgid wrapper C program that calls my script. The kernel should instead provide a simple API, that setuid/setgid on programfiles works in the same manner no matter how the program is implemented. But anyway, I got the answer I was looking for. Case closed. -----Original Message----- From: Derek Fountain [mailto:derekfountain@yahoo.co.uk] Sent: 19. januar 2004 10:31 To: suse-programming-e(a)suse.com Subject: Re: [suse-programming-e] Set uid on executables > Why do not pids.sh also report euid=0? Does this mean setuid/setgid on > bash scripts are useless and misleading? Basically, yes. A better way of looking at it is that setuid scripts are a security nightmare - the shell is so easy to corrupt that it's very hard to make a setuid script safe. For this reason the kernel doesn't allow them. This is a good thing - honest! -- > eatapple core dump -- To unsubscribe, email: suse-programming-e-unsubscribe(a)suse.com For additional commands, email: suse-programming-e-help(a)suse.com Archives can be found at: http://lists.suse.com/archive/suse-programming-e

1 0

Set uid on executables
by Hallingstad Håkon 19 Jan '04

19 Jan '04

I have two programs that (for all practical purposes) should be identical. root@dirac:/tmp/ cat pids.c #include <stdlib.h> int main(int argc, const char *argv[]) { return system("/usr/bin/id"); } root@dirac:/tmp/ cat pids.sh #! /bin/bash /usr/bin/id root@dirac:/tmp/ ls -l pids* -rwsr-xr-x 1 root root 4814 Jan 18 23:16 pids -rw-rw-rw- 1 root root 95 Jan 18 23:16 pids.c -rwsr-xr-x 1 root root 25 Jan 19 09:38 pids.sh root@dirac:/tmp/ su - hakonhal hakonhal@dirac:~/ cd /tmp hakonhal@dirac:/tmp/ ./pids uid=1000(hakonhal) gid=1000(hakonhal) euid=0(root) groups=1000(hakonhal),24(cdrom),40(src),100(users) hakonhal@dirac:/tmp/ ./pids.sh uid=1000(hakonhal) gid=1000(hakonhal) groups=1000(hakonhal),24(cdrom),40(src),100(users) hakonhal@dirac:/tmp/ Why do not pids.sh also report euid=0? Does this mean setuid/setgid on bash scripts are useless and misleading? Regards, Håkon Hallingstad

2 1

RE: [suse-programming-e] libpthread.so.0 not found trying to link simple app. Library is present in /lib
by Gustavo Dutra 15 Jan '04

15 Jan '04

Hi, It should work if you put -lpthread only. BTW, did you install pthread-dev(something like that) rpm??? -----Mensaje original----- De: Burt Bicksler [mailto:bbicksler@fortresstech.com] Enviado el: Thursday, January 15, 2004 4:10 PM Para: suse-programming-e(a)suse.com Asunto: [suse-programming-e] libpthread.so.0 not found trying to link simple app. Library is present in /lib Hi, I'm trying to build a simple hello world test application using pthreads. This is on a stock SUSE Pro 8.2 installation with all of the latest patches installed. During the link the linker whines that it cannot find libpthread.so.0. I have tried presenting this as -l/lib/libpthread.so.0 (which is where the lib physically resides). This doesn't change the problem, still no joy with linking the application. I'm probably doing something wrong, but I've scanned the web with Google and, while I've found similar problems with other libraries mentioned all of those appear to be related to not having the library installed. I haven't been able to track down a good specific example showing what library to link with, so I'm making the assumption that libpthread.so.0 is the correct one, but it doesn't appear to be recognized by the linker. Has anyone else encountered this problem, and if so what was the solution? If you can point me to a specific document that details the settings to use to build a "hello world" threaded application on SUSE 8.2 that would be great. Thanks, Burt --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.558 / Virus Database: 350 - Release Date: 1/2/2004

1 0

C++ compile problem. error in function
by ged.suse 14 Jan '04

14 Jan '04

Can anyone please, please show me what's going wrong here. (Full code listed at end of post) I'm trying to access a structure from within another structure but am receiving errors. Unfortunately, I need to build this on a windows machine, but I think I have made the code fully portable for Linux. It compiles with the mingw compiler anyway. Structures are global and are as follows: struct StockItem { int code; char desc[20]; float price; }stock[NUM_OF_ITEMS]; struct BillLine { StockItem stock; float weight; float cost; }bill_line[50]; The 'stock' array is already populated. All I'm trying to do is fill the 'BillLine bill_line' array in the first function, and then print out the array values in the second. My error seems to be coming from accessing one structure from another. My problem code is as follows, I've commented the line numbers flagged up by the compiler: BillLine bill_item(void) { BillLine bill; int item; cls(); cout << "Enter item number purchased: "; cin >> item; item -= 1; /*line 213*/ bill.stock = stock[item]; cout << "Weight: "; cin >> bill.weight; bill.cost = stock[item].price * bill.weight; return (bill); } void print_bill ( BillLine bill_line[50], int num_bill_items ) { for (int i=0; i<num_bill_items; ++i) { /*line 240*/ cout << "Name = " << bill_line[i].stock.desc << endl; cout << "Weight = " << bill_line[i].weight << endl; cout << "Cost = " << bill_line[i].cost << endl; } } MY compile log is as follows: Compiler: Default compiler Executing g++.exe... g++.exe "C:\Ged\code\assignment\best.cpp" -o "C:\Ged\code\assignment\best.exe" -g3 -O0 -g3 -I"C:\Ged\Dev-Cpp\include\c++" -I"C:\Ged\Dev-Cpp\include\c++\mingw32" -I"C:\Ged\Dev-Cpp\include\c++\backward" -I"C:\Ged\Dev-Cpp\include" -L"C:\Ged\Dev-Cpp\lib" C:/Ged/code/assignment/best.cpp: In function `BillLine bill_item()': C:/Ged/code/assignment/best.cpp:213: incompatible types in assignment of ` StockItem' to `StockItem[125]' C:/Ged/code/assignment/best.cpp: In function `void print_bill(BillLine*, int)': C:/Ged/code/assignment/best.cpp:240: request for member `desc' in `(bill_line + (+(i * 3508)))->BillLine::stock', which is of non-aggregate type ` StockItem[125]' Execution terminated The rest of the program runs fine. Although there is not much error checking (I'll add that later) there are no warnings when compiled. My full program code is as follows #include <iostream> #include <fstream> #include <conio.h> //for getch() using namespace std; const int NUM_OF_ITEMS = 125; struct StockItem { int code; char desc[20]; float price; }stock[NUM_OF_ITEMS]; struct BillLine { StockItem stock[NUM_OF_ITEMS]; float weight; float cost; }bill_line[50]; void cls(void) { system("cls"); } //function designed to aid portability. void disp_menu( void ); StockItem enter_data( void ); void delete_data( StockItem* ); void see_stock( StockItem*, int ); void writeToDisk( StockItem*, int ); int readFromDisk( StockItem* ); BillLine bill_item( void ); void print_bill ( BillLine*, int ); int main() { int ans, ctr; int num_stock_items = 0; int num_bill_items = 0; do { do { disp_menu(); cin >> ans; } while ((ans<1) || (ans>9)); switch (ans) { case 1: stock[num_stock_items] = enter_data(); num_stock_items++; break; case 2: delete_data( stock ); num_stock_items -= 1; break; case 3: see_stock(stock, num_stock_items); break; case 4: writeToDisk( stock, num_stock_items ); // NOT writing the whole array to disk. break; case 5: num_stock_items = readFromDisk( stock ); // setting the number items we read from file break; case 6: bill_line[num_bill_items] = bill_item(); num_bill_items++; break; case 7: print_bill( bill_line, num_bill_items ); break; default: break; } }while (ans!=8); return 0; } void disp_menu() { cout << "\n*** The Corner Shop ***\n\n"; cout << "Select an option: \n\n"; cout << "\t1. Enter new stock item " << endl; cout << "\t2. Delete stock item " << endl; cout << "\t3. See current stock " << endl; cout << "\t4. Save stock to disk " << endl; cout << "\t5. Load stock from disk " << endl; cout << "\t6. Enter purchase order " << endl; cout << "\t7. Print Bill " << endl; cout << "\t8. Exit \n" << endl; cout << "option> "; } StockItem enter_data(void) { StockItem stock_item; cls(); cout << "\n\nWhat is the product code: "; cin >> stock_item.code; cout << "What is the product description: "; cin.ignore(); cin.getline(stock_item.desc, 20); cout << "What is the product price: "; cin >> stock_item.price; cls(); return (stock_item); } void delete_data(StockItem stock[NUM_OF_ITEMS] ) { StockItem stock_temp[NUM_OF_ITEMS]; int item, n=0; cls(); cout << "Enter item to delete "; cin >> item; item -= 1; for(int i = 0; i < NUM_OF_ITEMS; i++) { if(i == item) ++n; stock_temp[i] = stock[n]; ++n; } for(int i = 0; i < NUM_OF_ITEMS; i++) stock[i] = stock_temp[i]; cls(); } void see_stock(StockItem stock[NUM_OF_ITEMS], int num_stock_items) { int ctr; cls(); cout << "\n\nHere is the stock listing:\n\n"; for (ctr = 0; ctr < num_stock_items; ++ctr) { cout << "Item " << ctr+1 << endl; cout << "Product Code: " << stock[ctr].code << endl; cout << "Product Description: " << stock[ctr].desc << endl; cout << "Price: " << stock[ctr].price << endl; cout << "------------------------------------------------\n"; } cout << "\nHit any key to continue.....\n"; getch(); cls(); } void writeToDisk( StockItem* array, int numOfItems ) { ofstream outfile( "items.txt" ); if (outfile.bad()) { cout << "\n*** Error opening file ***\n"; } for( int index = 0; index < numOfItems; index++ ) outfile.write( (char*)&array[index], sizeof(StockItem) ); cls(); } int readFromDisk( StockItem* array ) { int numOfItems = 0; ifstream infile( "items.txt" ); if (infile.bad()) { cout << "\n*** Error opening file ***\n"; } StockItem tmp_stockItem; // read from the file until we reach EOF while( infile.read( (char*)&tmp_stockItem, sizeof(tmp_stockItem) ) ) { // after a successfull read we store the the item into the array memcpy( &array[numOfItems], &tmp_stockItem, sizeof( array[numOfItems] ) ); numOfItems++; } cls(); // returning the number of array items we read from the file return numOfItems; } BillLine bill_item(void) { BillLine bill; int item; cls(); cout << "Enter item number purchased: "; cin >> item; item -= 1; bill.stock = stock[item]; cout << "Weight: "; cin >> bill.weight; bill.cost = stock[item].price * bill.weight; return (bill); } void print_bill ( BillLine bill_line[50], int num_bill_items ) { for (int i=0; i<num_bill_items; ++i) { cout << "Name = " << bill_line[i].stock.desc << endl; cout << "Weight = " << bill_line[i].weight << endl; cout << "Cost = " << bill_line[i].cost << endl; } }

5 13

USB device
by expatriate 13 Jan '04

13 Jan '04

Hello I'm interested in some reading material on how to open/ioctl/read/write a /dev/usb/xxx device. Does anyone know of a good text/website? TIA & Cheers

1 0

Please unsubscribe me from suse-programming-e@suse.com
by Twort, Richard 12 Jan '04

12 Jan '04

-----Original Message----- From: suse-programming-e-help(a)suse.com [mailto:suse-programming-e-help@suse.com] Sent: Wednesday, 2 July 2003 8:28 a.m. To: Twort, Richard Subject: confirm subscribe to suse-programming-e(a)suse.com Hi! This is the ezmlm program. I'm managing the suse-programming-e(a)suse.com mailing list. I'm working for my owner, who can be reached at suse-programming-e-owner(a)suse.com. To confirm that you would like richard.twort(a)openpolytechnic.ac.nz added to the suse-programming-e mailing list, please send an empty reply to this address: suse-programming-e-sc.1057091266.jpmliljoeajbalnfcgel-richard.twort=openpolytechnic.ac.nz(a)suse.com Usually, this happens when you just hit the "reply" button. If this does not work, simply copy the address and paste it into the "To:" field of a new message. or click here: mailto:suse-programming-e-sc.1057091266.jpmliljoeajbalnfcgel-richard.twort=openpolytechnic.ac.nz@suse.com This confirmation serves two purposes. First, it verifies that I am able to get mail through to you. Second, it protects you in case someone forges a subscription request in your name. --- Administrative commands for the suse-programming-e list --- I can handle administrative requests automatically. Please do not send them to the list address! Instead, send your message to the correct command address: For help and a description of available commands, send a message to: <suse-programming-e-help(a)suse.com> To subscribe to the list, send a message to: <suse-programming-e-subscribe(a)suse.com> To remove your address from the list, just send a message to the address in the ``List-Unsubscribe'' header of any list message. If you haven't changed addresses since subscribing, you can also send a message to: <suse-programming-e-unsubscribe(a)suse.com> For addition or removal of addresses, I'll send a confirmation message to that address. When you receive it, simply reply to it to complete the transaction. If you need to get in touch with the human owner of this list, please send a message to: <suse-programming-e-owner(a)suse.com> Please include a FORWARDED list message with ALL HEADERS intact to make it easier to help you. --- Enclosed is a copy of the request I received. Return-Path: <richard.twort(a)openpolytechnic.ac.nz> Received: (qmail 3939 invoked from network); 1 Jul 2003 20:27:45 -0000 Received: from ns.suse.de (HELO Cantor.suse.de) (213.95.15.193) by 0 with SMTP; 1 Jul 2003 20:27:45 -0000 Received: from Hermes.suse.de (Hermes.suse.de [213.95.15.136]) by Cantor.suse.de (Postfix) with ESMTP id 00F35150C5 for <suse-programming-e-subscribe(a)lists.suse.com>; Tue, 1 Jul 2003 22:27:44 +0200 (MEST) Received: from Cantor.suse.de (ns.suse.de [213.95.15.193]) by Hermes.suse.de (Postfix) with ESMTP id EFDE01104 for <suse-programming-e-subscribe(a)suse.com>; Tue, 1 Jul 2003 22:27:44 +0200 (CEST) Received: from turing.suse.de (Turing.suse.de [213.95.15.200]) by Cantor.suse.de (Postfix) with ESMTP id E7002150C5 for <suse-programming-e-subscribe(a)suse.com>; Tue, 1 Jul 2003 22:27:44 +0200 (MEST) Date: Tue, 1 Jul 2003 22:27:44 +0200 From: richard.twort(a)openpolytechnic.ac.nz Message-Id: <200307012027.h61KRik29102(a)turing.suse.de> To: undisclosed-recipients: ;

1 0

(C++) Saving / reading structures to / from disk (desperate measures)
by ged.suse＠ntlworld.com 08 Jan '04

08 Jan '04

Thanks to all who have helped so far :) I don't have much time left to get this program running, so I have opted to drop the functions and try and get it running in the main()..... ....however, I still can't get it to do what I want. Can anyone PLEASE help me with this. I would be very grateful, I need to get this program running. Cade now as follows: #include <iostream> #include <fstream> using namespace std; struct StockItem { int code; char desc[20]; float price; }stock[125]; /*struct bill_line { StockItem product; float weight; float cost; }; struct bill { bill_line items[20]; int num_lines; };*/ void disp_menu(void); struct StockItem enter_data(); void see_stock(StockItem stock[125], int num_items); main() { int ans, ctr; int num_items = 0; FILE *item_file = NULL; do { do { disp_menu(); cin >> ans; } while ((ans<1) || (ans>6)); switch (ans) { case 1: stock[num_items] = enter_data(); num_items++; break; case 2: see_stock(stock, num_items); break; case 3: { item_file = fopen("items.txt", "ab"); for (ctr=0;ctr<125;++ctr) { fwrite(&stock[ctr], sizeof(StockItem), 3, item_file); } fclose(item_file); break; } case 4: { item_file = fopen("items.txt", "rb"); for (ctr=0;ctr<125;++ctr) { fread(&stock[ctr], sizeof(StockItem), 3, item_file); } fclose(item_file); break; } default: break; } }while (ans!=5); return 0; system("PAUSE"); return 0; } void disp_menu() { cout << "\n*** The Corner Shop ***\n\n"; cout << "Select an option: \n\n"; cout << "\t1. Enter new stock " << endl; cout << "\t2. See current stock " << endl; cout << "\t3. Save stock to disk " << endl; cout << "\t4. Load stock from disk " << endl; cout << "\t5. Exit \n" << endl; cout << "option> "; } StockItem enter_data() { StockItem stock_item; cout << "\n\nWhat is the product code: "; cin >> stock_item.code; cout << "What is the product description: "; fflush(stdin); cin.getline(stock_item.desc, 20); cout << "What is the product price: "; cin >> stock_item.price; return (stock_item); } void see_stock(StockItem stock[125], int num_items) { int ctr; char ret; cout << "\n\nHere is the stock listing:\n\n"; for (ctr = 0; ctr < num_items; ++ctr) { cout << "Item " << ctr+1 << endl; cout << "Product Code: " << stock[ctr].code << endl; cout << "Product Description: " << stock[ctr].desc << endl; cout << "Price: " << stock[ctr].price << endl; cout << "------------------------------------------------\n"; } } > > From: Salman Khilji <skhilji(a)tampabay.rr.com> > Date: 2004/01/06 Tue AM 06:32:27 GMT > To: ged.suse(a)ntlworld.com > Subject: Re: [suse-programming-e] (C++) Saving / reading structures to / from disk > > Sorry I don't have time to give you a complete implementation, but lets see > what I can pull out of my brain. the following won't compile, but will give > you a brief idea as how to read and write a structure to/from disk. The > following will NOT work with structure that have embedded pointers in them. > > > example: > > struct Foo { > float bar; > int john; > }; > > Foo array[2]; > > ... populate the array of structs... > > FILE * file = fopen("myfile", "w+b"); > fwrite(file, array, sizeof(array)); // I know the arguments are wrong here, > but lookup the docs to correct it. > > > To read it back, first use fopen call and read it into a char array. > > Then do this. > > Foo * array; > > array = (Foo*) myCharArray; > > After this, you should be able to see what the contents of Foo are. > > > I have an example that does this, but its at my office and I will have to dig > it out. > > Salman > > ----------------------------------------- Email provided by http://www.ntlhome.com/

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Re: [suse-programming-e] Tips for PCRE expressions?
by Mark Gray 08 Jan '04

08 Jan '04

Trey Gruel <drathos-suse(a)nightmoose.net> writes: >> Secondly, it is almost always a mistake to try to do all your work >> using a single regex -- use multiple regex's and program logic based >> on the results. > One of the reasons I'm trying to move things to regex is so the simpler > checks can be edited in config files that can be reloaded on the fly. Have you considered embedding a perl interpreter in your program? Not such overkill if you have a lot of configuration that you would like to be that flexible. (For one regex, it would be overkill though:-) > If this check ends up being a problem, I may end up making an option for a > "negative check" where it'll match invalid values. Prolly not a bad idea > anyway.. This is what the perl cookbook 2nd edition (page 61) gives for a VALID C float: ^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$ and pcretest seems to like it: markgray@soyo:/ARK/BOOKS/perlcookbook2/ch02> pcretest PCRE version 4.4 21-August-2003 re> /^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/ data> 123.45 0: 123.45 1: 2: .45 data> -123.45 0: -123.45 1: - 2: .45 data> unkn No match data> NaN No match data> abcdef No match data> +123.456e+02 0: +123.456e+02 1: + 2: .456 3: e+02 4: +02 data>

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Re: [suse-programming-e] Tips for PCRE expressions?
by Mark Gray 08 Jan '04

08 Jan '04

Trey Gruel <drathos-suse(a)nightmoose.net> writes: > I'm trying to implement some data checking using PCRE for regular > expressions. My experience using regex is fairly limited and very > rusty. For the most part, I've been able to replace most of the > simple C based checks with regex, but I'm having trouble with one > that I think should be possible with regex. > What I'm having trouble with is a check of an alphanumeric field (up > to 10 characters) that lets everything *except* UNK, UNKN, and > UNKNOWN through (logic being if it's unknown, it should be blank). > I was thinking I should be able to do this with look-ahead or > look-behind assertion, but I can't seem to make it work. > Any ideas would be appreciated. First off, get ahold of a copy of: Mastering Regular Expressions, 2nd Edition By Jeffrey E. F. Friedl 2nd Edition July 2002 ISBN 0-596-00289-0, Order Number: 2890 484 pages, $39.95 US, $61.95 CA, 28.50 UK O'Reilly Secondly, it is almost always a mistake to try to do all your work using a single regex -- use multiple regex's and program logic based on the results.

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Tips for PCRE expressions?
by Trey Gruel 07 Jan '04

07 Jan '04

I'm trying to implement some data checking using PCRE for regular expressions. My experience using regex is fairly limited and very rusty. For the most part, I've been able to replace most of the simple C based checks with regex, but I'm having trouble with one that I think should be possible with regex. What I'm having trouble with is a check of an alphanumeric field (up to 10 characters) that lets everything *except* UNK, UNKN, and UNKNOWN through (logic being if it's unknown, it should be blank). I was thinking I should be able to do this with look-ahead or look-behind assertion, but I can't seem to make it work. Any ideas would be appreciated. -- trey

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Re: (forw) [suse-programming-e] SuSE-9.0 /usr/include/wx/html/htmlproc.h left out of wxGTK-devel package
by Michal Čihař 07 Jan '04

07 Jan '04

Hi > ----- Forwarded message from Mark Gray <markgray-temp-1072781312(a)iago.nac.net> ----- > While this might not be > the only bug in wxGTK-devel (I am still working my way through the > samples) /usr/include/wx/html/htmlproc.h is not packaged up to be > installed in the wxGTK-devel package (which causes html/test/test.cpp > to fail to compile) Copying htmlproc.h from the source package to > /usr/include/wx/html/ fixes the problem. Well this is bug in wxWindows install scripts (they have there manually maintained list of files to install). I reported it to their bugs (bug #872377). I'll make some more checks what other headers are not installed before next release. -- Best Regards, Michal Cihar SUSE CR, s.r.o.

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SuSE-9.0 /usr/include/wx/html/htmlproc.h left out of wxGTK-devel package
by Mark Gray 07 Jan '04

07 Jan '04

Since feedback(a)suse.com no longer exists, and I cannot use feedback.cgi from my shell account, I thought I ought to report this here in hopes someone from SuSE might see it. While this might not be the only bug in wxGTK-devel (I am still working my way through the samples) /usr/include/wx/html/htmlproc.h is not packaged up to be installed in the wxGTK-devel package (which causes html/test/test.cpp to fail to compile) Copying htmlproc.h from the source package to /usr/include/wx/html/ fixes the problem. (wxGTK is a fast, very powerful and beautiful collection of widgets by the way.)

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Re: (C++) Saving / reading structures to / from disk
by Ged 07 Jan '04

07 Jan '04

Hi Davi, I understand what you mean. however this also gives the same output file as before. My main problem is getting the data back into the program after I have exited and restarted. This is what I have been stuck with for the past few days. I'm beginning to think its not possible (although I know it is) as nobody, including experienced coders on c++ forums seems to be able to get it to work. If you get a second, could you compile the code and run the program, you'll see what I mean. Thanks, Ged. On Tuesday 06 January 2004 19:32, davicastro(a)terra.com.br wrote: > The main error is at: > > void save_data(StockItem * tosave) > .... > fout.write((char *) &tosave, sizeof(tosave)); > > sizeof(tosave) is the same of sizeof(StockItem *), and probably 4 bytes. > Furthermore, you should not use the & before tosave, since it is already > a pointer (array). The same mistake occurs in the load code. > If you want to store a C array you should also store its size (and also > pass it as argument to others functions). If you want to fix this code, you > should read some more about C pointers and arrays until everything get > clear. Then it will be straightforward. > > []s > Davi > -=SuSE Linux 9.0=-

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Someone tell me
by bruno berisso summers 07 Jan '04

07 Jan '04

where I can reed a good guie about programing in UNIX? Thankes and sorry about mi inglish _________________________________________________________________ Charla con tus amigos en línea mediante MSN Messenger: http://messenger.latino.msn.com/

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emacs starts faster than qt "Hello World!" -- Does anyone use wxGTK?
by Mark Gray 06 Jan '04

06 Jan '04

The good news with SuSE-9.0 is that emacs starts almost instantly once you remove unneeded startup files from site-lib (my compliments to GNU and SuSE). The bad news is that qt applications start up slower with every release -- the example "Hello World!" takes 5-10 seconds to start. I just got through compiling the examples for the wxGTK c++, library, and I am thoroughly impressed with how fast they start. Does anyone on this list use wxGTK in "real" world applications?

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(C++) Saving / reading structures to / from disk
by ged.suse＠ntlworld.com 05 Jan '04

05 Jan '04

Hi all, I hate to ask like this as I normally like to work things out for myself, but I am running out of ideas....and hair !!! I am writing a stock inventory program using structures. The program data is initially populated by hand, and then there is an option to save the array of structures to disk. If the program is exited, the data will need to be inserted back into the program, hence the load function. My main problem is, I can't get these 2 functions to work. I have been working on this section for nearly 3 days now, and do not seem to be getting anywhere. I do not know any programmers to ask for help, so am relying on forums, but I have only been programming for about 2-3 months, so its difficult to implement what advise people give you. The program compiles, and I think the problem may lie in the way the data is being passed to the functions, but I am not experienced enough yet to solve it. Would anyone be able to get these functions working for me please. I have a lot more code to put into this program, but I can't move on until this part is complete. Like I said, I would not normally ask like this, but I am running out of options. Thanks to anyone who can help me, my code so far is as follows: #include <iostream> #include <fstream> using namespace std; struct StockItem { int code; char desc[20]; float price; } stock[125]; /*struct bill_line { StockItem product; float weight; float cost; }; struct bill { bill_line items[20]; int num_lines; };*/ void disp_menu(void); struct StockItem enter_data(); void see_stock(StockItem stock[125], int num_items); void save_data(StockItem * tosave); StockItem *load_data(StockItem toload[]); int main() { //StockItem stock[125]; int ans; int num_items = 0; do { do { disp_menu(); cin >> ans; } while((ans < 1) || (ans > 6)); switch (ans) { case 1: stock[num_items] = enter_data(); num_items++; break; case 2: see_stock(stock, num_items); break; case 3: save_data(stock[ctr]); break; case 4: { //StockItem temp[125]; StockItem *eerrmm = load_data(stock); break; } default: break; } } while(ans != 5); return 0; } void disp_menu() { cout << "\n*** The Corner Shop ***\n\n"; cout << "Select an option: \n\n"; cout << "\t1. Enter new stock " << endl; cout << "\t2. See current stock " << endl; cout << "\t3. Save stock to disk " << endl; cout << "\t4. Load stock from disk " << endl; cout << "\t5. Exit \n" << endl; cout << "option> "; } StockItem enter_data() { StockItem stock_item; cout << "\n\nWhat is the product code: "; cin >> stock_item.code; cout << "What is the product description: "; fflush(stdin); cin.getline(stock_item.desc, 20); cout << "What is the product price: "; cin >> stock_item.price; return (stock_item); } void see_stock(StockItem stock[125], int num_items) { int ctr; char ret; cout << "\n\nHere is the stock listing:\n\n"; for(ctr = 0; ctr < num_items; ++ctr) { cout << "Item " << ctr + 1 << endl; cout << "Product Code: " << stock[ctr].code << endl; cout << "Product Description: " << stock[ctr].desc << endl; cout << "Price: " << stock[ctr].price << endl; cout << "------------------------------------------------\n"; } cout << "Press any key to return to the menu"; if(cin >> ret) return; } //Problem sections void save_data(StockItem * tosave) { ofstream fout("items.txt", ios::binary); if(!fout) { cout << "\n*** Error opening file ***\n"; } fout.write((char *) &tosave, sizeof(tosave)); fout.close(); } StockItem *load_data(StockItem * toload) { ifstream fin("items.txt", ios::binary); if(!fin) { cout << "\n*** Error opening file ***\n"; } fin.read((char *) &toload, sizeof(toload)); fin.close(); cout << toload; return toload; } ----------------------------------------- Email provided by http://www.ntlhome.com/

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any resource for Linux C++
by Ivan Sergio Borgonovo 04 Jan '04

04 Jan '04

I need to learn how to deal with threads, daemons and redirection in C++. I'll surely have to learn more about *nix particularly Linux and C++. I'm expecially looking for simple code samples and libraries. A framework of a multi threaded C++ daemon will be a perfect starting. With the exception of http://www.boost.org/ I didn't find anything interesting. Also any pointer to C++ and Linux mailing lists will be welcome. THX

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A good book on C programming?
by Gavin Henry 02 Jan '04

02 Jan '04

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi all, During my degree, BEng (Hons) Electronics and Communications Engineering, we did C programming every year, but I never kept it up, as I had no interest and didn't see the point. But now I really want to get back into it as I see a point with GNU/Linux. I want to get my old skills back and write something or help on some projects etc. I need some good books. I used to have one called "A Book On C", but sold it, and I have been reading various tutorials on the web and the many devoted websites. Anyone have any recommendations? One more question, should I go for C or C++? Which will benefit me more with GNU/Linux? Thanks for your time, Gavin. - -- Regards http://www.magicfx.co.uk http://www.suretecsystems.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (GNU/Linux) iD8DBQE/7e1UgNqd7Kng8UoRAqnYAKDWL9XQcMVkiUpLJheJQbx5nHDT/ACgzCM9 BCo4TWvJOFuyj9r815nIv50= =x9hf -----END PGP SIGNATURE-----

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Re: [suse-programming-e] SuSE-9.0 gcc-3.3.1 optimization turns off important warning
by Mark Gray 01 Jan '04

01 Jan '04

Marcus Meissner <meissner(a)suse.de> writes: > On Wed, Dec 31, 2003 at 09:22:36AM -0500, Mark Gray wrote: [snip] >> It is the toupper that turns it off then: >> >> markgray@soyo:/usr/src/packages/BUILD/bug> cat xx.c >> #include <ctype.h> >> >> void strupr_OLD (char *s) >> { >> while (*s) { >> *s++ = toupper(*s); >> } >> } >> >> markgray@soyo:/usr/src/packages/BUILD/bug> gcc -O2 -Wall -c xx.c >> markgray@soyo:/usr/src/packages/BUILD/bug> >> >> (This is also 9.0 btw) > Hmm. Probably because *s++ = toupper(*s); is translated by a macro to: > > *s++ = (__extension__ ({ int __res; if (sizeof (*s) > 1) { if (__builtin_constant_p (*s)) { int __c = (*s); __res = __c < -128 || __c > 255 ? __c : (*__ctype_toupper_loc ())[__c]; } else __res = toupper (*s); } else __res = (*__ctype_toupper_loc ())[(int) (*s)]; __res; })); > > Might be to hard for the compiler to spot the problem. As an assembly language programmer, I find it highly amusing that such a macro generates so few machine instructions :-)

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