fork

问题 I'd like to fork a subprocess in python that does not run an external command ... it would just run a defined function. And I want to capture stdout and stderr separately. I know how to use os.fork() and os.pipe() , but that mechanism only gives me two fd's to work with. I'm looking for three fd's: one for stdin , one for stdout , and one for stderr . This is easy to manage using subprocess.Popen when running an external command, but that function doesn't seem to allow a local function to be

问题 I need to implement concurrent matrix multiplication in C using multiple processes. I understand that because each process has its own private address space, I will have to use some form of interprocess communication (IPC). I did some looking around and couldn't find many implementations that didn't use threads. I was wondering if anyone knew the most best way to go about this, either using shared memory, message passing, or pipes? I am not asking for a solution, but rather, if anyone knows,

问题 I'm wondering if I have to wait() for all child process to finish in the parent program? I have read the manuals and some online resources about fork(), but none of them mentioned that a wait() in the parent is enforced. However, if I do not wait in the parent program, the process does not terminate but just does nothing until I press enter, and than terminates. 回答1: If the parent process doesn't use a system call of the wait() -family for its children processes, it could simply die first.

问题 I'm trying to write a very basic HTTP server. I want to separate the server and the service in two separate executable (similar to inetd). So I have a generic server, that forks a service and execute its code using exec. The main loop is as follows: while(true) { int client_sock; if ((client_sock = accept(server_sock, (struct sockaddr *) NULL, NULL)) < 0) { return -1; } pid_t pid = fork(); if (pid == 0) { close(server_sock); close(0); dup(client_sock); close(1); dup(client_sock); execvp(argv

问题 I am trying to use setrlimit to limit the number of processes a program can create. Here is my code: struct rlimit limiter; getrlimit( RLIMIT_NPROC, &limiter ); limiter.rlim_max = limiter.rlim_cur = 10; setrlimit( RLIMIT_NPROC, &limiter ); int val = fork(); printf( "Error number %d\n", errno ); //gives 11 if( val == -1 ) { printf( "Fork failed\n" ); } else if( val ) { printf( "parent\n" ); } else { printf("child\n" ); } return 0; Since the value of rlim_max and rlim_cur is 10, my program

问题 I'm trying to create a daemon process that handles several child threads. But the child thread doesn't seem to send the signal back to the parent to call the function. i have tried to take it out of the class and make it a standard function but that doesn't seem to help either. class Daemon { public function __construct() { $set = pcntl_signal(SIGCHLD, array($this, 'childSignalHandler')); $pid = pcntl_fork(); if ($pid == -1) { echo 'could not fork'; } elseif ($pid) { // parent sleep(20); //

问题 I fork()'d a child process and created pipes between them and am able to send argument argv[1] to the child. I want the child to take that filename provided from argv[1] and perform an execl("/bin/cat","cat",(char *) 0); How do I route the filename piped to the child to the execl? Enclose is my code for clearity : int main(int argc, char ** argv){ int fds[2]; char buffer[100]; int status; if(pipe(fds) == -1){ perror("pipe creation failed"); exit(EXIT_FAILURE); } switch (fork()){ case 0:/

问题 I am trying to use the raw clone system, but I could not find any proper documentation. I tried to write a small program to try it, but this ends up with a segmentation fault. I cannot understand where I am wrong. here is the small application : define STACK_SIZE 0x10000 define BUFSIZE 200 #define _GNU_SOURCE void hello (){ fprintf(stderr,"Hello word\n"); _exit(0); } int main() { int res; void *stack = mmap(0, STACK_SIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); pid_t ptid,

问题 we use delayed job in our web application and we need multiple delayed jobs workers happening parallelly, but we don't know how many will be needed. solution i currently try is running one worker and calling fork/Process.detach inside the needed task. i was trying to run fork directly in rails application previously but it didnt work too good with passenger. this solution seems to work well. could there be any caveats in production? 回答1: one issue which happened to me today and which anyone

问题 I'm trying a small unit-testing here. But the program doesn't work as I expected. char *args[2]; args[0] = (char*)"/usr/bin/firefox"; args[1] = NULL; pid = fork(); printf("forked and my pid is %d\n",pid); //check for errors if (pid<0){ printf("Error: invoking fork to start ss has failed, Exiting\n "); exit(1); } //the child process runs firefox if (pid==0){ if (execv(args[0],args)<0){ perror("Error: running s with execvp has failed, Exiting\n"); } printf("IVE BEEN KILLED\n"); } //dad is here