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  • How to R/W hard disk when CPU is in Protect Mode?

    - by smwikipedia
    I am doing some OS experiment. Until now, all my code utilized the real mode BIOS interrupt to manipulate hard disk and floppy. But once my code enabled the Protect Mode of the CPU, all the real mode BIOS interrupt service routine won't be available. How could I R/W the hard disk and floppy? I have a feeling that I need to do some hardware drivers now. Am I right? Is this why an OS is so difficult to develop? I know that hardwares are all controlled by reading from and writing to certain control or data registers. For example, I know that the Command Block Registers of hard disk range from 0x1F0 to 0x1F7. But I am wondering whether the register addresses of so many different hardwares are the same on the PC platform? Or do I have to detect that before using them? How to detect them?? For any responses I present my deep appreciation.

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  • Ubuntu makes noise and heat when AC charger is inserted

    - by user2263752
    I have an issue with heat and noise on my laptop with Ubuntu 14.04 installed. The thing is that when I have the AC charger plugged into the laptop, it automatically goes to "boost mode" or something. And when the laptop is on battery mode, the heat and noise is reduced shortly. I want the laptop to be on battery mode as general and "boost mode" as an option if more power is needed. Any solutions? I have installed tlp that doesn't seen to have any effect.

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  • Question with "extern" in C

    - by why
    When programming, I would like to split one large file(which contains main function) to many small files, so there is one common case: functions in small files can modify the var from main file, so i think extern is very useful! for instance: in main.c extern int i = 100; in small.c extern int i; fprintf(stdout, "var from main file: %d\n", i); I just want to know is my understanding right?

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  • Parsing line with delimiter in Python

    - by neversaint
    I have lines of data which I want to parse. The data looks like this: a score=216 expect=1.05e-06 a score=180 expect=0.0394 What I want to do is to have a subroutine that parse them and return 2 values (score and expect) for each line. However this function of mine doesn't seem to work: def scoreEvalFromMaf(mafLines): for word in mafLines[0]: if word.startswith("score="): theScore = word.split('=')[1] theEval = word.split('=')[2] return [theScore, theEval] raise Exception("encountered an alignment without a score") Please advice what's the right way to do it?

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  • Bash:Redirection Halts

    - by user365828
    I have a command e.g. ls-l file.txt When there is insufficient space on my drive, the above command just stalls waiting for something to happen. Does anyone know about a code that I could write enabling me to display a message about the lack of space on my drive? E.g. could I use IPC or do you have any other ideas? Thanks in advance.

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  • Fade unfocused GNU Emacs frame (X window)

    - by Mischa Arefiev
    Is it possible to make GNU Emacs 24 dim unfocused windows a bit? For example, I can set my rxvt-unicode clients to become darker when their windows don't have focus with this string in ~/.Xdefaults: URxvt*fading: 50 It greatly reduces discomfort when you have a lot of terminal windows on 2+ monitors. I would like a similar feature in Emacs, but couldn't google up anything. Here is how it looks like with urxvt (png, 1.43 MB)

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  • Address of instruction causing SIGSEGV in external program

    - by karramba
    I want to get address of instruction that causes external program to SIGSEGV. I tried using ptrace for this, but I'm getting EIP from kernel space (probably default signal handler?). How GDB is able to get the correct EIP? Is there a way to make GDB provide this information using some API? edit: I don't have sources of the program, only binary executable. I need automation, so I can't simply use "run", "info registers" in GDB. I want to implement "info registers" in my own mini-debugger :)

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  • MP3 and OGG tags in PHP

    - by Quamis
    Except http://us3.php.net/manual/en/book.ktaglib.php and http://getid3.sourceforge.net/ does anyone know of any other way to work from PHP with tags on audio files? I need to read and write them, and KTagLib seems a little too much for the job, and also don't really get the documentation, and getID3 seems to only write ID3v1 tags.

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  • Is there a way to find a specific file and then change into the directory containing it in one go?

    - by bergyman
    I'm looking for a way to find what I know will be a unique file, and then change into the directory containing that file. Something along the lines of: find . -name 'Subscription.java' | xargs cd Or: find . -name 'Subscription.java' -exec cd {} \; I know this won't work because it's both trying to cd supplying the entire absolute path, which contains the file, and also because xargs can't do any built in shell commands...but you get the point of what I want to accomplish.

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  • spin_lock_irqsave vs spin_lock_irq

    - by cojocar
    On a SMP machine we must use spin_lock_irqsave and not spin_lock_irq from interrupt context. Why would we want to save the flags (which contains the IF)? Is there another interrupt routine that could interrupt us? The flags are per CPU?

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  • Appending rather than overwriting files when moving

    - by ukas1
    I have the following directory structure: +-archive +-a +-data.txt +-b +-data.txt +-incoming +-a +-data.txt +-c +-data.txt How do I do the equivalent of mv incoming/* archive/ but have the contents of the files in incoming appended to those in archive rather than overwrite them?

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  • sigprocmask not working

    - by EpsilonVector
    I'm using sigprocmask as follows: void mask(){ sigset_t new_set,old_set; sigemptyset(&new_set); sigaddset(&new_set,SIGALRM); sigprocmask(SIG_BLOCK, &new_set, &old_set); } and to my surprise a function which prints a big list somehow gets interrupted by the signal, even though I invoke mask() at its beginning. It looks as if mask fails, since my function doesn't invoke any other functions and therefore nowhere in its run should an unmask() happen. What can cause sigprocmask to fail?

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  • Using /dev/tcp instead of wget

    - by User1
    Why does this work: exec 3</dev/tcp/www.google.com/80 echo -e "GET / HTTP/1.1\n\n"&3 cat <&3 And this fail: echo -e "GET / HTTP/1.1\n\n" /dev/tcp/www.google.com/80 cat </dev/tcp/www.google.com/80 Is there a way to do it in one-line w/o using wget, curl, or some other library?

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  • appending text to all files that starts with a string

    - by learner135
    How do I append a string to all the files in a directory that starts with a particular string? I tried, cat mysig >> F* But instead of appending contents of mysig to all files starting with F, it creates a file named "F*". Obviously wildcard doesn't seem to work. Any alternatives? Thanks in advance. Edit: Also how do I delete this newly created file "F*" safely?. Using rm F* would delete all the files starting with F which I wouldn't want.

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  • BASH: Checking for environment variables

    - by Hamza
    Hi folks, I am trying to check the value of an environment variable and depending on the value do certain things and it works fine as long as the variable is set. When it isn't though I get a whole bunch of errors (as BASH is trying to compare the string I specify with an undefined variable, I guess) I tried implementing an extra check to prevent it happening but no luck. The block of code I am using is: #!/bin/bash if [ -n $TESTVAR ] then if [ $TESTVAR == "x" ] then echo "foo" exit elif [ $TESTVAR == "y" ] then echo "bar" exit else echo "baz" exit fi else echo -e "TESTVAR not set\n" fi And this the output: $ export TESTVAR=x $ ./testenv.sh foo $ export TESTVAR=y $ ./testenv.sh bar $ export TESTVAR=q $ ./testenv.sh baz $ unset TESTVAR $ ./testenv.sh ./testenv.sh: line 5: [: ==: unary operator expected ./testenv.sh: line 9: [: ==: unary operator expected baz My question is, shouldn't 'unset TESTVAR' nullify it? It doesn't seem to be the case... Thanks.

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  • Process is killed without a (obvious) reason and program stops working

    - by Krzysiek Gurniak
    Here's what my program is supposed to do: create 4 child processes: process 0 is reading 1 byte at a time from STDIN, then writing it into FIFO process 1 is reading this 1 byte from fifo and write its value as HEX into shared memory process 2 is reading HEX value from shared memory and writing it into pipe finally process 3 is reading from pipe and writing into STDOUT (in my case: terminal) I can't change communication channels. FIFO, then shared memory, then pipes are the only option. My problem: Program stops at random moments when some file is directed into stdin (for example:./program < /dev/urandom). Sometimes after writing 5 HEX values, sometimes after 100. Weird thing is that when it is working and in another terminal I write "pstree -c" there is 1 main process with 4 children processes (which is what I want), but when I write "pstree -c" after it stopped writing (but still runs) there are only 3 child processes. For some reason 1 is gone even though they all have while(1) in them.. I think I might have problem with synchronization here, but I am unable to spot it (I've tried for many hours). Here's the code: #include <unistd.h> #include <fcntl.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/shm.h> #include <sys/sem.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/stat.h> #include <string.h> #include <signal.h> #define BUFSIZE 1 #define R 0 #define W 1 // processes ID pid_t p0, p1, p2, p3; // FIFO variables int fifo_fd; unsigned char bufor[BUFSIZE] = {}; unsigned char bufor1[BUFSIZE] = {}; // Shared memory variables key_t key; int shmid; char * tab; // zmienne do pipes int file_des[2]; char bufor_pipe[BUFSIZE*30] = {}; void proces0() { ssize_t n; while(1) { fifo_fd = open("/tmp/fifo",O_WRONLY); if(fifo_fd == -1) { perror("blad przy otwieraniu kolejki FIFO w p0\n"); exit(1); } n = read(STDIN_FILENO, bufor, BUFSIZE); if(n<0) { perror("read error w p0\n"); exit(1); } if(n > 0) { if(write(fifo_fd, bufor, n) != n) { perror("blad zapisu do kolejki fifo w p0\n"); exit(1); } memset(bufor, 0, n); // czyszczenie bufora } close(fifo_fd); } } void proces1() { ssize_t m, x; char wartosc_hex[30] = {}; while(1) { if(tab[0] == 0) { fifo_fd = open("/tmp/fifo", O_RDONLY); // otwiera plik typu fifo do odczytu if(fifo_fd == -1) { perror("blad przy otwieraniu kolejki FIFO w p1\n"); exit(1); } m = read(fifo_fd, bufor1, BUFSIZE); x = m; if(x < 0) { perror("read error p1\n"); exit(1); } if(x > 0) { // Konwersja na HEX if(bufor1[0] < 16) { if(bufor1[0] == 10) // gdy enter { sprintf(wartosc_hex, "0x0%X\n", bufor1[0]); } else { sprintf(wartosc_hex, "0x0%X ", bufor1[0]); } } else { sprintf(wartosc_hex, "0x%X ", bufor1[0]); } // poczekaj az pamiec bedzie pusta (gotowa do zapisu) strcpy(&tab[0], wartosc_hex); memset(bufor1, 0, sizeof(bufor1)); // czyszczenie bufora memset(wartosc_hex, 0, sizeof(wartosc_hex)); // przygotowanie tablicy na zapis wartosci hex x = 0; } close(fifo_fd); } } } void proces2() { close(file_des[0]); // zablokuj kanal do odczytu while(1) { if(tab[0] != 0) { if(write(file_des[1], tab, strlen(tab)) != strlen(tab)) { perror("blad write w p2"); exit(1); } // wyczysc pamiec dzielona by przyjac kolejny bajt memset(tab, 0, sizeof(tab)); } } } void proces3() { ssize_t n; close(file_des[1]); // zablokuj kanal do zapisu while(1) { if(tab[0] == 0) { if((n = read(file_des[0], bufor_pipe, sizeof(bufor_pipe))) > 0) { if(write(STDOUT_FILENO, bufor_pipe, n) != n) { perror("write error w proces3()"); exit(1); } memset(bufor_pipe, 0, sizeof(bufor_pipe)); } } } } int main(void) { key = 5678; int status; // Tworzenie plikow przechowujacych ID procesow int des_pid[2] = {}; char bufor_proces[50] = {}; mknod("pid0", S_IFREG | 0777, 0); mknod("pid1", S_IFREG | 0777, 0); mknod("pid2", S_IFREG | 0777, 0); mknod("pid3", S_IFREG | 0777, 0); // Tworzenie semaforow key_t klucz; klucz = ftok(".", 'a'); // na podstawie pliku i pojedynczego znaku id wyznacza klucz semafora if(klucz == -1) { perror("blad wyznaczania klucza semafora"); exit(1); } semafor = semget(klucz, 1, IPC_CREAT | 0777); // tworzy na podstawie klucza semafor. 1 - ilosc semaforow if(semafor == -1) { perror("blad przy tworzeniu semafora"); exit(1); } if(semctl(semafor, 0, SETVAL, 0) == -1) // ustawia poczatkowa wartosc semafora (klucz, numer w zbiorze od 0, polecenie, argument 0/1/2) { perror("blad przy ustawianiu wartosci poczatkowej semafora"); exit(1); } // Tworzenie lacza nazwanego FIFO if(access("/tmp/fifo", F_OK) == -1) // sprawdza czy plik istnieje, jesli nie - tworzy go { if(mkfifo("/tmp/fifo", 0777) != 0) { perror("blad tworzenia FIFO w main"); exit(1); } } // Tworzenie pamieci dzielonej // Lista pamieci wspoldzielonych, komenda "ipcs" // usuwanie pamieci wspoldzielonej, komenta "ipcrm -m ID_PAMIECI" shmid = shmget(key, (BUFSIZE*30), 0666 | IPC_CREAT); if(shmid == -1) { perror("shmget"); exit(1); } tab = (char *) shmat(shmid, NULL, 0); if(tab == (char *)(-1)) { perror("shmat"); exit(1); } memset(tab, 0, (BUFSIZE*30)); // Tworzenie lacza nienazwanego pipe if(pipe(file_des) == -1) { perror("pipe"); exit(1); } // Tworzenie procesow potomnych if(!(p0 = fork())) { des_pid[W] = open("pid0", O_WRONLY | O_TRUNC | O_CREAT); // 1 - zapis, 0 - odczyt sprintf(bufor_proces, "Proces0 ma ID: %d\n", getpid()); if(write(des_pid[W], bufor_proces, sizeof(bufor_proces)) != sizeof(bufor_proces)) { perror("blad przy zapisie pid do pliku w p0"); exit(1); } close(des_pid[W]); proces0(); } else if(p0 == -1) { perror("blad przy p0 fork w main"); exit(1); } else { if(!(p1 = fork())) { des_pid[W] = open("pid1", O_WRONLY | O_TRUNC | O_CREAT); // 1 - zapis, 0 - odczyt sprintf(bufor_proces, "Proces1 ma ID: %d\n", getpid()); if(write(des_pid[W], bufor_proces, sizeof(bufor_proces)) != sizeof(bufor_proces)) { perror("blad przy zapisie pid do pliku w p1"); exit(1); } close(des_pid[W]); proces1(); } else if(p1 == -1) { perror("blad przy p1 fork w main"); exit(1); } else { if(!(p2 = fork())) { des_pid[W] = open("pid2", O_WRONLY | O_TRUNC | O_CREAT); // 1 - zapis, 0 - odczyt sprintf(bufor_proces, "Proces2 ma ID: %d\n", getpid()); if(write(des_pid[W], bufor_proces, sizeof(bufor_proces)) != sizeof(bufor_proces)) { perror("blad przy zapisie pid do pliku w p2"); exit(1); } close(des_pid[W]); proces2(); } else if(p2 == -1) { perror("blad przy p2 fork w main"); exit(1); } else { if(!(p3 = fork())) { des_pid[W] = open("pid3", O_WRONLY | O_TRUNC | O_CREAT); // 1 - zapis, 0 - odczyt sprintf(bufor_proces, "Proces3 ma ID: %d\n", getpid()); if(write(des_pid[W], bufor_proces, sizeof(bufor_proces)) != sizeof(bufor_proces)) { perror("blad przy zapisie pid do pliku w p3"); exit(1); } close(des_pid[W]); proces3(); } else if(p3 == -1) { perror("blad przy p3 fork w main"); exit(1); } else { // proces macierzysty waitpid(p0, &status, 0); waitpid(p1, &status, 0); waitpid(p2, &status, 0); waitpid(p3, &status, 0); //wait(NULL); unlink("/tmp/fifo"); shmdt(tab); // odlaczenie pamieci dzielonej shmctl(shmid, IPC_RMID, NULL); // usuwanie pamieci wspoldzielonej printf("\nKONIEC PROGRAMU\n"); } } } } exit(0); }

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  • Why I'm not getting "Multiple definition" error from the g++?

    - by ban
    I tried to link my executable program with 2 static libraries using g++. The 2 static libraries have the same function name. I'm expecting a "multiple definition" linking error from the linker, but I did not received. Can anyone help to explain why is this so? staticLibA.h #ifndef _STATIC_LIBA_HEADER #define _STATIC_LIBA_HEADER int hello(void); #endif staticLibA.cpp #include "staticLibA.h" int hello(void) { printf("\nI'm in staticLibA\n"); return 0; } output: g++ -c -Wall -fPIC -m32 -o staticLibA.o staticLibA.cpp ar -cvq ../libstaticLibA.a staticLibA.o a - staticLibA.o staticLibB.h #ifndef _STATIC_LIBB_HEADER #define _STATIC_LIBB_HEADER int hello(void); #endif staticLibB.cpp #include "staticLibB.h" int hello(void) { printf("\nI'm in staticLibB\n"); return 0; } output: g++ -c -Wall -fPIC -m32 -o staticLibB.o staticLibB.cpp ar -cvq ../libstaticLibB.a staticLibB.o a - staticLibB.o main.cpp extern int hello(void); int main(void) { hello(); return 0; } output: g++ -c -o main.o main.cpp g++ -o multipleLibsTest main.o -L. -lstaticLibA -lstaticLibB -lstaticLibC -ldl -lpthread -lrt

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  • How to maipulate the shell output in php

    - by Mirage
    I am trying to write php script which does some shell functions like reporting. So i am starting with diskusage report I want in following format drive path ------------total-size --------free-space Nothing else My script is $output = shell_exec('df -h -T'); echo "<pre>$output</pre>"; and its ouput is like below Filesystem Type Size Used Avail Use% Mounted on /dev/sda6 ext3 92G 6.6G 81G 8% / none devtmpfs 3.9G 216K 3.9G 1% /dev none tmpfs 4.0G 176K 4.0G 1% /dev/shm none tmpfs 4.0G 1.1M 4.0G 1% /var/run none tmpfs 4.0G 0 4.0G 0% /var/lock none tmpfs 4.0G 0 4.0G 0% /lib/init/rw /dev/sdb1 ext3 459G 232G 204G 54% /media/Server /dev/sdb2 fuseblk 466G 254G 212G 55% /media/BACKUPS /dev/sda5 fuseblk 738G 243G 495G 33% /media/virtual_machines How can i convert that ouput into my forn\matted output

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  • kernel get stack when signalled

    - by yoavstr
    hi there i write readers and writers where the kernel have to syncronize between them and block writer who already read a massage when i am in the queue waiting I get signal so I do the fallowing while (i_Allready_Read(myf) == ALLREADY_READ || isExistWriter == false ) //while (!(i_Allready_Read(aliveProc,current->pid))) { int i, is_sig = 0; printk(KERN_INFO "\n\n*****entered set in read ******\n\n" ); if (i_Allready_Read(myf) == ALLREADY_READ ) wait_event_interruptible (readWaitQ1, !i_Allready_Read(myf)); else wait_event_interruptible (readWaitQ1, isExistWriter); //printk(KERN_INFO "Read Wakeup %d\n",current->pid); for (i = 0; i < _NSIG_WORDS && !is_sig; i++) { is_sig = current->pending.signal.sig[i] & ~current->blocked.sig[i]; } if (is_sig) { handledClose(myf); module_put (THIS_MODULE); return -EINTR; } } return 0;//success } inline void handledClose(struct file *myf)//v { /* *if we close the writer other writer *would be able to enter to permissiones */ if (myf == writerpid ) { isExistWriter = DOESNT_EXIST; //printk(KERN_INFO "procfs_close : this is pid that just closed %d \n", writerpid); } /* *else its a reader so our numofreaders *need to decremented */ else { removeFromArr(myf); numOfReaders--; } } and my close does nothing ... what did i do wrong?

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  • KSH: Variables containing double quotes

    - by nitrobass24
    I have a string called STRING1 that could contain double quotes. I am echoing the string through sed to pull out puntuation then sending to array to count certain words. The problem is I cannot echo variables through double quotes to sed. I am crawling our filesystems looking for files that use FTP commands. I grep each file for "FTP" STRING1=`grep -i ftp $filename` If you echo $STRING1 this is the output (just one example) myserver> echo "Your file `basename $1` is too large to e-mail. You must ftp the file to BMC tech support. \c" echo "Then, ftp it to ftp.bmc.com with the user name 'anonymous.' \c" echo "When the ftp is successful, notify technical support by phone (800-537-1813) or by e-mail ([email protected].)" Then I have this code STRING2=`echo $STRING1|sed 's/[^a-zA-Z0-9]/ /g'` I have tried double quoting $STRING1 like STRING2=`echo "$STRING1"|sed 's/[^a-zA-Z0-9]/ /g'` But that does not work. Single Qoutes, just sends $STRING1 as the string to sed...so that did not work. What else can I do here?

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  • Bash scripting - Iterating through "variable" variable names for a list of associative arrays

    - by user1550254
    I've got a variable list of associative arrays that I want to iterate through and retrieve their key/value pairs. I iterate through a single associative array by listing all its keys and getting the values, ie. for key in "${!queue1[@]}" do echo "key : $key" echo "value : ${queue1[$key]}" done The tricky part is that the names of the associative arrays are variable variables, e.g. given count = 5, the associative arrays would be named queue1, queue2, queue3, queue4, queue5. I'm trying to replace the sequence above based on a count, but so far every combination of parentheses and eval has not yielded much more then bad substitution errors. e.g below: for count in {1,2,3,4,5} do for key in "${!queue${count}[@]}" do echo "key : $key" echo "value : ${queue${count}[$key]}" done done Help would be very much appreciated!

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