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• Why fork() before setsid()

  - by corentin.kerisit

  Why fork() before setsid() to daemonize a process ? Basically, if I want to detach a process from its controlling terminal and make it a process group leader : I use setsid(). Doing this without forking before doesn't work. Why ? Thanks :)

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• forks in C - exercise

  - by Zka

  I try to repeat and learn more advanced uses and options when cutting trees with forks in the jungle of C. But foolishly I find an example which should be very easy as I have worked with forks before and even written some code, but i can't understand it fully. Here comes : main() { if (fork() == 0) { if (fork() == 0) { printf("3"); } else if ((wait(NULL)) > 0) { printf("2"); } } else { if (fork() == 0) { printf("1"); exit(0); } if (fork() == 0) { printf("4"); } } printf("0"); return 0; } Possible solutions are : 3201040 3104200 1040302 4321000 4030201 1403020 where 2, 5 and 6 are correct answers. First of all, shouldn't there be four zeroes in the output? Second... How does one come to the solution at all? Been doing this on paper for almost an hour and I'm not even close to understanding why the given solution are more correct than the false ones (except for nr3 as it can't end with 2 since a 0 must follow). Anyone with his forks in check who can offer some good explanation?

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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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• Git Submodule or fork

  - by Eric

  I have a private repo in github that is the complete source code to my cms. Now I have a few local customers that I want to use the same code base on but with different themes. Is it better to fork the original project out into a repo for each one. Or use a submodule and create a new repo for each customer? After each site is complete I would imagine the theme files wouldn't change much but would need to pull in changes from the main repo when bugs are discovered.

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• os.fork() sem_wait: Permission denied

  - by Roger

  I am trying to compile python 2.5 on AIX 6.1, and the following occurs: Python 2.6.5 (r265:79063, Jun 3 2010, 11:43:45) [GCC 4.2.0] on aix6 Type "help", "copyright", "credits" or "license" for more information. >>> import os >>> os.fork() 0 sem_wait: Permission denied 741398 I have found this bug, which sounds similar: http://bugs.python.org/issue1234 which suggests setting HAVE_BROKEN_POSIX_SEMAPHORES I have tried this by modifying the configure script, and I can see it being set, but that does not help.. Any ideas ??

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• How to handle inputs in a C shell program during exec

  - by hits_lucky

  I am currently writing my own shell program. This simple shell can just execute commands. When executing commands like vi or calc which require input from the terminal , the command is getting executed and is waiting for the input from the user. But I am unable to give any input on the screen. How should the input be handled during the fork and exec. Here is the piece of code which is executing commands: if((pid = fork()) < 0) { perror("Fork failed"); exit(errno); } if(pid == 0) { // Child process if(execvp(arguments[0], arguments) == -1) { child_status = errno; switch(child_status) { case ENOENT: printf(" command not found \n"); break; } exit(errno); } } else { // parent process int wait_stat; if(waitpid(pid , &wait_stat, WNOHANG) == -1) { printf(" waitpid failed \n"); return; } } } ~ Thanks,

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• Github without merging

  - by tfmoraes

  I have the following situation: A software hosted at github. 4 developers, each have her own fork in github. Each developer creates and develops using branches in her own fork. Given that we use branches to develop, we want to merge our branches (in our forks) to the upstream repo. How do I merge in github without using pull request? Is it possible to merge to upstream from my own fork? Thanks in advance.

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• Fork or copy a users browser session in IE

  - by jmoeller

  Is it possible to fork a users session (or do something similar) in a Internet Explorer plugin? I want to process the page the user is on when they click a button in the toolbar. To avoid interrupting the users browsing, I'd like to "copy" everything so I can parse and process the page in the background. The processing can involve things such as loading the content of the result links on a Google search, if that's where the button was clicked. So - what I basically want is to imitate "Ctrl+N" but hide the window from the user, so they won't be interrupted. As you can see, if you fill out and submit the form on http://www.snee.com/xml/crud/posttest.html and press "Ctrl+N", everything posted will still appear in the new window, but it won't post the data twice. I was thinking of somehow copying the IWebBrowser2, but: I'm not sure if that's possible (I haven't been able to find any information on MSDN) I don't know if it copies the sessions as well. Creating a new instance of the IWebBrowser2 and simply navigating to the current URL isn't a valid solution as POST-variables of course doesn't get carried over.

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• Forking in PHP on Windows

  - by Doug Kavendek

  We are running PHP on a Windows server (a source of many problems indeed, but migrating is not an option currently). There are a few points where a user-initiated action will need to kick off a few things that take a while and about which the user doesn't need to know if they succeed or fail, such as sending off an email or making sure some third-party accounts are updated. If I could just fork with pcntl_fork(), this would be very simple, but the PCNTL functions are not available in Windows. It seems the closest I can get is to do something of this nature: exec( 'php-cgi.exe somescript.php' ); However, this would be far more complicated. The actions I need to kick off rely on a lot of context that already will exist in the running process; to use the above example, I'd need to figure out the essential data and supply it to the new script in some way. If I could fork, it'd just be a matter of letting the parent process return early, leaving the child to work on a few more things. I've found a few people talking about their own work in getting various PCNTL functions compiled on Windows, but none seemed to have anything available (broken links, etc). Despite this question having practically the same name as mine, it seems the problem was more execution timeout than needing to fork. So, is my best option to just refactor a bit to deal with calling php-cgi, or are there other options? Edit: It seems exec() won't work for this, at least not without me figuring some other aspect of it, as it waits until the call returns. I figured I could use START, sort of like exec( 'start php-cgi.exe somescript.php' );, but it still waits until the other script finishes.

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• Does waitpid yield valid status information for a child process that has already exited?

  - by dtrebbien

  If I fork a child process, and the child process exits before the parent even calls waitpid, then is the exit status information that is set by waitpid still valid? If so, when does it become not valid; i.e., how do I ensure that I can call waitpid on the child pid and continue to get valid exit status information after an arbitrary amount of time, and how do I "clean up" (tell the OS that I am no longer interested in the exit status information for the finished child process)? I was playing around with the following code, and it appears that the exit status information is valid for at least a few seconds after the child finishes, but I do not know for how long or how to inform the OS that I won't be calling waitpid again: #include <assert.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/wait.h> int main() { pid_t pid = fork(); if (pid < 0) { fprintf(stderr, "Failed to fork\n"); return EXIT_FAILURE; } else if (pid == 0) { // code for child process _exit(17); } else { // code for parent sleep(3); int status; waitpid(pid, &status, 0); waitpid(pid, &status, 0); // call `waitpid` again just to see if the first call had an effect assert(WIFEXITED(status)); assert(WEXITSTATUS(status) == 17); } return EXIT_SUCCESS; }

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• Packaging python software with custom dependencies

  - by viraptor

  Hi, I'm looking for a good way to package a Python application that is going to be deployed on a Debian server. The application itself depends on some modules which are not included in base Debian repository, although they might be in the future. This creates some problems... I depend on some patches to those modules. If the original module gets installed one day, the application will break. However if I install everything I need in a virtualenv just for that application, I lose the ability to upgrade Python itself (in case of security updates). The third option would be to rename my fork of the upstream module and just treat it as a completely separate one. But that would mean changing the code (not much work, but it wouldn't be that clean / universal anymore). Are there any other options that I missed? Are there any pros / cons I didn't see in the solutions above?

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• Which MySQL Fork/Version to Pick??

  - by Drew

  As most of you know, Sun acquired MySQL (and later Oracle acquired Sun), and during these acquisitions, there were a lot of FUD in MySQL community which resulted in creation of various forks. Today we have MySQL from MySQL, Percona (XtraDB) MySQL, OurDelta MySQL, MariaDB, Drizzle to name a few. Which brings us to the source of the problem. We are in the process of upgrading our databases (hardware/software) and I would like to know which one of the forks should I go with. Each has their own set of pros/cons. We are currently using MySQL 5.0.x from MySQL/Linux on an 8-core machine. Our new hardware is a monster with 32 cores and 32GB of memory connecting to a fast NetApp Storage via FC. I would like to stick with MySQL from MySQL but I have heard horror stories on how badly MySQL 5.1 performs on many cores. I have also heard that MySQL 5.4 performs better on multi-core machines but that's still not production ready. In addition, I have also heard a lot of good things about Percona builds. This is what I know so far: MySQL 5.1 from MySQL: Reliable choice, but doesn't scale well on a big machine Percona: Scales well, good backing company. I don't have much experience with it MariaDB: Don't know much about it besides that it was founded by Original MySQL developers (including Monty) OurDelta: Don't know much Drizzle: Mostly optimized for cloud computing I would like to know what's the general notion about this problem. Which build/version should I go with? How are you guys picking your builds/versions? Thanks!

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• Running daemon through rsh

  - by Max

  I want to run program as daemon in remote machine in Unix. I have rsh connection and I want the program to be running after disconnection. Suppose I have two programs: util.cpp and forker.cpp. util.cpp is some utility, for our purpose let it be just infinite root. util.cpp int main() { while (true) {}; return 0; } forker.cpp takes some program and run it in separe process through fork() and execve(): forker.cpp #include <stdio.h> #include <errno.h> #include <stdlib.h> #include <unistd.h> int main(int argc, char** argv) { if (argc != 2) { printf("./a.out <program_to_fork>\n"); exit(1); } pid_t pid; if ((pid = fork()) < 0) { perror("fork error."); exit(1); } else if (!pid) { // Child. if (execve(argv[1], &(argv[1]), NULL) == -1) { perror("execve error."); exit(1); } } else { // Parent: do nothing. } return 0; } If I run: ./forker util forker is finished very quickly, and bash 'is not paused', and util is running as daemon. But if I run: scp forker remote_server://some_path/ scp program remote_server://some_path/ rsh remote_server 'cd /some_path; ./forker program' then it is all the same (i.e. at the remote_sever forker is finishing quickly, util is running) but my bash in local machine is paused. It is waiting for util stopping (I checked it. If util.cpp is returning than it is ok.), but I don't understand why?! There are two questions: 1) Why is it paused when I run it through rsh? I am sure that I chose some stupid way to run daemon. So 2) How to run some program as daemon in C/C++ in unix-like platforms. Tnx!

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• Etiquette: Version bump my fork of opensource project?

  - by Ross

  This question is about etiquette and open source projects. I have forked an application from github and added two new features. The first feature has been request frequently elsewhere. I have added it. Code & implementation are clean (I think). The second feature is more of a hack. It will be of use to others, but the implementation is a little dirty in useage and more so in code. I need the feature but I don't have the skills to fully implement it properly or to a level that could be considered a worth while contrabution to the main project. How should the versioning work? Do I just bump up my version numbers care-free and push to my master branch? It is annoying to know which version is running, modifed or original, as both have the same version number. But will it be confusing when, months later, my github page has a version number the same as the original but both are actually completely different. (I have made pull requests etc. but that is not the context of my question.) The project I have forked uses ruby jeweler so has a versioning format of: Jeweler tracks the version of your project. It assumes you will be using a version in the format x.y.z. x is the 'major' version, y is the 'minor' version, and z is the patch version. Is this standard for other projects/langauges too? Are my changes patches? Thanks

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• What happens to a SIGINT (^C) when sent to a perl script containing children?

  - by CmdrGuard

  I have a Perl script that forks. Each fork runs an external program, parses the output, and converts the output to a Storable file. The Storable files are then read in by the parent and the total data from each of the children are analyzed before proceeding onto a repeat of the previous fork or else the parent stops. What exactly happens when I issue a ^C while some of the children are still running the external program? The parent perl script was called in the foreground and, I presume, remained in the foreground despite the forking. Is the SIGINT passed to all children, that is, the parent, the parent's children, and the external program called by the children??

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• What to do if exec() fails?

  - by Grigory

  Let's suppose we have a code doing something like this: int pipes[2]; pipe(pipes); pid_t p = fork(); if(0 == p) { dup2(pipes[1], STDOUT_FILENO); execv("/path/to/my/program", NULL); ... } else { //... parent process stuff } As you can see, it's creating a pipe, forking and using the pipe to read the child's output (I can't use popen here, because I also need the PID of the child process for other purposes). Question is, what should happen if in the above code, execv fails? Should I call exit() or abort()? As far as I know, those functions close the open file descriptors. Since fork-ed process inherits the parent's file descriptors, does it mean that the file descriptors used by the parent process will become unusable?

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• How to fork my android app?

  - by eidylon

  So I've written my first Android app, ... and want to be able to provide both free and paid versions. I wrote and compiled it in Eclipse on Windows. I'm wondering if it is possible, and how I would go about doing so, to have separate compile jobs somehow, so that I can maintain my free and paid versions from one set of source code, and just leave out certain bits for the paid version, but keep the main source the same. What are the recommended ways/best practices for devving a paid and free version of the same app from one set of source? Is it even possible?

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• What options do individual have to fork a project?

  - by skrco

  Let's assume our example individual has an idea, engagement, ... to fork project. By project I mean any kind of software - thick client, web site, portal, service, driver, plc, ... - anything that can be programmed. Motto of question: What options do our example individual have to fork this project from the early beginning through getting collaborators and users to mature software? Here are the main subquestions: Sandbox phase: Where can he announce his idea and proposal and receive positive/negative critic and feedback? Development phase: Where can he build his team to work on this project? Yet deployed phase: Where can he schedule tasks, assign tickets and bugs to be solved? and the list can go on... What really interests me is the "sandbox phase question".

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• Why does fprintf start printing out of order or not at all?

  - by Steve Melvin

  This code should take an integer, create pipes, spawn two children, wait until they are dead, and start all over again. However, around the third time around the loop I lose my prompt to enter a number and it no longer prints the number I've entered. Any ideas? #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #define WRITE 1 #define READ 0 int main (int argc, const char * argv[]) { //Pipe file-descriptor array unsigned int isChildA = 0; int pipeA[2]; int pipeB[2]; int num = 0; while(1){ fprintf(stderr,"Enter an integer: "); scanf("%i", &num); if(num == 0){ fprintf(stderr,"You entered zero, exiting...\n"); exit(0); } //Open Pipes if(pipe(pipeA) < 0){ fprintf(stderr,"Could not create pipe A.\n"); exit(1); } if(pipe(pipeB) < 0){ fprintf(stderr,"Could not create pipe B.\n"); exit(1); } fprintf(stderr,"Value read: %i \n", num); fprintf(stderr,"Parent PID: %i\n", getpid()); pid_t procID = fork(); switch (procID) { case -1: fprintf(stderr,"Fork error, quitting...\n"); exit(1); break; case 0: isChildA = 1; break; default: procID = fork(); if (procID<0) { fprintf(stderr,"Fork error, quitting...\n"); exit(1); } else if(procID == 0){ isChildA = 0; } else { write(pipeA[WRITE], &num, sizeof(int)); close(pipeA[WRITE]); close(pipeA[READ]); close(pipeB[WRITE]); close(pipeB[READ]); pid_t pid; while (pid = waitpid(-1, NULL, 0)) { if (errno == ECHILD) { break; } } } break; } if (procID == 0) { //We're a child, do kid-stuff. ssize_t bytesRead = 0; int response; while (1) { while (bytesRead == 0) { bytesRead = read((isChildA?pipeA[READ]:pipeB[READ]), &response, sizeof(int)); } if (response < 2) { //Kill other child and self fprintf(stderr, "Terminating PROCID: %i\n", getpid()); write((isChildA?pipeB[WRITE]:pipeA[WRITE]), &response, sizeof(int)); close(pipeA[WRITE]); close(pipeA[READ]); close(pipeB[WRITE]); close(pipeB[READ]); return 0; } else if(!(response%2)){ //Even response/=2; fprintf(stderr,"PROCID: %i, VALUE: %i\n", getpid(), response); write((isChildA?pipeB[WRITE]:pipeA[WRITE]), &response, sizeof(int)); bytesRead = 0; } else { //Odd response*=3; response++; fprintf(stderr,"PROCID: %i, VALUE: %i\n", getpid(), response); write((isChildA?pipeB[WRITE]:pipeA[WRITE]), &response, sizeof(int)); bytesRead = 0; } } } } return 0; } This is the output I am getting... bash-3.00$ ./proj2 Enter an integer: 101 Value read: 101 Parent PID: 9379 PROCID: 9380, VALUE: 304 PROCID: 9381, VALUE: 152 PROCID: 9380, VALUE: 76 PROCID: 9381, VALUE: 38 PROCID: 9380, VALUE: 19 PROCID: 9381, VALUE: 58 PROCID: 9380, VALUE: 29 PROCID: 9381, VALUE: 88 PROCID: 9380, VALUE: 44 PROCID: 9381, VALUE: 22 PROCID: 9380, VALUE: 11 PROCID: 9381, VALUE: 34 PROCID: 9380, VALUE: 17 PROCID: 9381, VALUE: 52 PROCID: 9380, VALUE: 26 PROCID: 9381, VALUE: 13 PROCID: 9380, VALUE: 40 PROCID: 9381, VALUE: 20 PROCID: 9380, VALUE: 10 PROCID: 9381, VALUE: 5 PROCID: 9380, VALUE: 16 PROCID: 9381, VALUE: 8 PROCID: 9380, VALUE: 4 PROCID: 9381, VALUE: 2 PROCID: 9380, VALUE: 1 Terminating PROCID: 9381 Terminating PROCID: 9380 Enter an integer: 102 Value read: 102 Parent PID: 9379 PROCID: 9386, VALUE: 51 PROCID: 9387, VALUE: 154 PROCID: 9386, VALUE: 77 PROCID: 9387, VALUE: 232 PROCID: 9386, VALUE: 116 PROCID: 9387, VALUE: 58 PROCID: 9386, VALUE: 29 PROCID: 9387, VALUE: 88 PROCID: 9386, VALUE: 44 PROCID: 9387, VALUE: 22 PROCID: 9386, VALUE: 11 PROCID: 9387, VALUE: 34 PROCID: 9386, VALUE: 17 PROCID: 9387, VALUE: 52 PROCID: 9386, VALUE: 26 PROCID: 9387, VALUE: 13 PROCID: 9386, VALUE: 40 PROCID: 9387, VALUE: 20 PROCID: 9386, VALUE: 10 PROCID: 9387, VALUE: 5 PROCID: 9386, VALUE: 16 PROCID: 9387, VALUE: 8 PROCID: 9386, VALUE: 4 PROCID: 9387, VALUE: 2 PROCID: 9386, VALUE: 1 Terminating PROCID: 9387 Terminating PROCID: 9386 Enter an integer: 104 Value read: 104 Parent PID: 9379 Enter an integer: PROCID: 9388, VALUE: 52 PROCID: 9389, VALUE: 26 PROCID: 9388, VALUE: 13 PROCID: 9389, VALUE: 40 PROCID: 9388, VALUE: 20 PROCID: 9389, VALUE: 10 PROCID: 9388, VALUE: 5 PROCID: 9389, VALUE: 16 PROCID: 9388, VALUE: 8 PROCID: 9389, VALUE: 4 PROCID: 9388, VALUE: 2 PROCID: 9389, VALUE: 1 Terminating PROCID: 9388 Terminating PROCID: 9389 105 Value read: 105 Parent PID: 9379 Enter an integer: PROCID: 9395, VALUE: 316 PROCID: 9396, VALUE: 158 PROCID: 9395, VALUE: 79 PROCID: 9396, VALUE: 238 PROCID: 9395, VALUE: 119 PROCID: 9396, VALUE: 358 PROCID: 9395, VALUE: 179 PROCID: 9396, VALUE: 538 PROCID: 9395, VALUE: 269 PROCID: 9396, VALUE: 808 PROCID: 9395, VALUE: 404 PROCID: 9396, VALUE: 202 PROCID: 9395, VALUE: 101 PROCID: 9396, VALUE: 304 PROCID: 9395, VALUE: 152 PROCID: 9396, VALUE: 76 PROCID: 9395, VALUE: 38 PROCID: 9396, VALUE: 19 PROCID: 9395, VALUE: 58 PROCID: 9396, VALUE: 29 PROCID: 9395, VALUE: 88 PROCID: 9396, VALUE: 44 PROCID: 9395, VALUE: 22 PROCID: 9396, VALUE: 11 PROCID: 9395, VALUE: 34 PROCID: 9396, VALUE: 17 PROCID: 9395, VALUE: 52 PROCID: 9396, VALUE: 26 PROCID: 9395, VALUE: 13 PROCID: 9396, VALUE: 40 PROCID: 9395, VALUE: 20 PROCID: 9396, VALUE: 10 PROCID: 9395, VALUE: 5 PROCID: 9396, VALUE: 16 PROCID: 9395, VALUE: 8 PROCID: 9396, VALUE: 4 PROCID: 9395, VALUE: 2 PROCID: 9396, VALUE: 1 Terminating PROCID: 9395 Terminating PROCID: 9396 105 Value read: 105 Parent PID: 9379 Enter an integer: PROCID: 9397, VALUE: 316 PROCID: 9398, VALUE: 158 PROCID: 9397, VALUE: 79 PROCID: 9398, VALUE: 238 PROCID: 9397, VALUE: 119 PROCID: 9398, VALUE: 358 PROCID: 9397, VALUE: 179 PROCID: 9398, VALUE: 538 PROCID: 9397, VALUE: 269 PROCID: 9398, VALUE: 808 PROCID: 9397, VALUE: 404 PROCID: 9398, VALUE: 202 PROCID: 9397, VALUE: 101 PROCID: 9398, VALUE: 304 PROCID: 9397, VALUE: 152 PROCID: 9398, VALUE: 76 PROCID: 9397, VALUE: 38 PROCID: 9398, VALUE: 19 PROCID: 9397, VALUE: 58 PROCID: 9398, VALUE: 29 PROCID: 9397, VALUE: 88 PROCID: 9398, VALUE: 44 PROCID: 9397, VALUE: 22 PROCID: 9398, VALUE: 11 PROCID: 9397, VALUE: 34 PROCID: 9398, VALUE: 17 PROCID: 9397, VALUE: 52 PROCID: 9398, VALUE: 26 PROCID: 9397, VALUE: 13 PROCID: 9398, VALUE: 40 PROCID: 9397, VALUE: 20 PROCID: 9398, VALUE: 10 PROCID: 9397, VALUE: 5 PROCID: 9398, VALUE: 16 PROCID: 9397, VALUE: 8 PROCID: 9398, VALUE: 4 PROCID: 9397, VALUE: 2 PROCID: 9398, VALUE: 1 Terminating PROCID: 9397 Terminating PROCID: 9398 106 Value read: 106 Parent PID: 9379 Enter an integer: PROCID: 9399, VALUE: 53 PROCID: 9400, VALUE: 160 PROCID: 9399, VALUE: 80 PROCID: 9400, VALUE: 40 PROCID: 9399, VALUE: 20 PROCID: 9400, VALUE: 10 PROCID: 9399, VALUE: 5 PROCID: 9400, VALUE: 16 PROCID: 9399, VALUE: 8 PROCID: 9400, VALUE: 4 PROCID: 9399, VALUE: 2 PROCID: 9400, VALUE: 1 Terminating PROCID: 9399 Terminating PROCID: 9400 ^C Another thing that's strange, when ran from within XCode it behaves normally. However, when ran from bash on Solaris or OSX it acts up.

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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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• Open Source MariaDB, the MySQL fork to replace MySQL?

  - by Jenson

  Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 Frankly speaking, I’ve been out of touch with the Open source world for quite some time. Until recently, after I’ve joined the new government agency, I managed to do some research while given time to learn new technologies and languages. I started reading tech blogs and tech news again (since I’m not as busy as before where I need to rush for project deadlines in and out), and I spotted this MariaDB that really attracts my attention, this is the link to ZDNet article - http://www.zdnet.com/open-source-mariadb-a-mysql-fork-challenges-oracle-7000008311/ Open-Source MariaDB, a MySQL fork, challenges Oracle Yes, you’re right, MariaDB is a MySQL fork, and as mentioned in the article, MariaDB is run by the founder of MySQL, Michael ‘Monty’ Widenius, and he claims MariaDB is faster, more secure and has more features than MySQL. I’m actually very excited to know that the code is maintained by the same dedicated core team of MySQL in the past 18 years. They even bother to form a foundation, the MariaDB Foundation, to promote MariaDB. Already, there’s a lot of open source software officially supporting MariaDB, such as  Drupal, Jelastic – Java in the cloud, Kajona, MediaWiki, phpMyAdmin, Plone, SaltOs, WordPress, and Zend Framework. But the hosting service provider might not be readily supporting MariaDB in their hosting solution. Normal 0 false false false EN-GB X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;} Time will tell whether MariaDB would be the real replacement for MySQL, I’m sorry I don’t think I should use alternative here ;-) For more information, please visit MariaDB official site. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

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• Reading a file N lines at a time in ruby

  - by Sam

  I have a large file (hundreds of megs) that consists of filenames, one per line. I need to loop through the list of filenames, and fork off a process for each filename. I want a maximum of 8 forked processes at a time and I don't want to read the whole filename list into RAM at once. I'm not even sure where to begin, can anyone help me out?

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• pthread and child process data sharing in C

  - by mustafabattal

  hi everyone, my question is somewhat conceptual, how is parent process' data shared with child process created by a "fork()" call or with a thread created by "pthread_create()" for example, are global variables directly passed into child process and if so, does modification on that variable made by child process effect value of it in parent process? i appreciate partial and complete answers in advance, if i'm missing any existing resource, i'm sorry, i've done some search on google but couldn't find good results thanks again for your time and answers

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• What perl function to use?

  - by user301087

  I'm setting something up to SSH out to several servers in 'batches'. I basically want to maintain 5 connections at a time, and when one finishes open up another (following an array of server IPs). I'm wondering for something like this should I be using fork()? If so, what logic can I use to ensure that the I maintain 5 children at a time?

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• Redirecting exec output to a buffer or file

  - by devin

  I'm writing a C program where I fork(), exec(), and wait(). I'd like to take the output of the program I exec'ed to write it to file or buffer. For example, if I exec ls I want to write file1 file2 etc to buffer/file. I don't think there is a way to read stdout, so does that mean I have to use a pipe? Is there a general procedure here that I haven't been able to find?

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