fork

问题 Here is a code: int i=0; pid_t pid; puts("Hello, World!"); puts(""); pid = fork(); if(pid) i=42; printf("%p\n", &i); printf("%d\n", i); puts(""); And output Hello, World! 0x7fffc2490278 42 0x7fffc2490278 0 Program print Hello, World! one time, so child process wasn't start from the beginning and it wasn't re-define variables. Adresses of variables are same. So they are same. But I change i's value in parent process which is executed first, it didn't change for child process. Why? 回答1:

问题 int x=0; int main() { for(i=0;i<2;i++) { fork(); x=x+5; } return 0; } I am a newbie to the fork() concept. Is the above tree (with x values) a correct solution for the C code mentioned above? The values in the nodes are the x values of their processes respectively. And also can we return values to the parent process from the child process? Suppose in the above example code can I return the x value of the child to the parent process? 回答1: You mean that's a process tree and in the bubbles is

问题 I'm trying to do a simple fork -> execute another program -> say "hello" to that child process -> read back something -> print what received. The program used as child just waits for any line of input and prints something to the stdout like "hello there!" This is my "host" program (that is not working): #include <sys/types.h> #include <unistd.h> #include <stdio.h> #define IN 0 #define OUT 1 #define CHILD 0 main () { pid_t pid; int pipefd[2]; FILE* output; char buf[256]; pipe(pipefd); pid =

问题 I saw the question Why does Process.fork make stuff slower in Ruby on OS X? and was able to determine that Process.fork does not actually make tasks, in general, slower. However, it does seem to make Time.utc , in particular, much slower. require 'benchmark' def do_stuff 50000.times { Time.utc(2016) } end puts "main: #{Benchmark.measure { do_stuff }}" Process.fork do puts "fork: #{Benchmark.measure { do_stuff }}" end Here are some results: main: 0.100000 0.000000 0.100000 ( 0.103762) fork: 0

问题 Does the Linux scheduler prefer to run the child process after fork() to the father process? Usually, the forked process will execute exec of some kind so, it is better to let child process to run before father process(to prevent copy on write). I assume that the child will execute exec as first operation after it will be created. Is my assumption (that the scheduler will prefer child process) correct. If not, why? If yes, is there more reasons to run child first? 回答1: To quote The Linux

问题 I'm working on Chromium fork. How can i replace Chromium resources and app package? Resources I've found that one day android_branding_res_dirs gn argument was introduced: @@ -43,10 +43,10 @@ # GYP: //chrome/chrome.gyp:chrome_java (resources part) android_resources("chrome_java_resources") { - resource_dirs = [ - "java/res", - "java/res_default", - ] + if (!defined(android_branding_res_dirs)) { + android_branding_res_dirs = [ "//chrome/android/java/res_chromium" ] + } + resource_dirs = [

问题 The following code never ends. Why is that? #include <sys/types.h> #include <stdio.h> #include <unistd.h> #define SIZE 5 int nums[SIZE] = {0, 1, 2, 3, 4}; int main() { int i; pid_t pid; pid = vfork(); if(pid == 0){ /* Child process */ for(i = 0; i < SIZE; i++){ nums[i] *= -i; printf(”CHILD: %d “, nums[i]); /* LINE X */ } } else if (pid > 0){ /* Parent process */ wait(NULL); for(i = 0; i < SIZE; i++) printf(”PARENT: %d “, nums[i]); /* LINE Y */ } return 0; } Update: This code is just to

问题 I have executed a block of code. And it is as shown below: #include<stdio.h> main() { int i=0; fork(); printf("The value of i is:%d\n",++i); fork(); printf("The value of j is:%d\n",++i); fork(); wait(); } And I got following output: The value of i is:1 The value of j is:2 The value of i is:1 The value of j is:2 The value of j is:2 pckoders@ubuntu:~$ The value of j is:2 Can anyone explain to me what role fork() and wait() functions play here? 回答1: The program generates a tree of processes. At

问题 I need help returning a "status code" from my child program back to the parent, where it will check the status code, print code, and exit the parent. This is for a class project, so I will put some relevant code here, but I don't to post the entire project for obvious reasons. I have forked and created the child process through exec. The parent does some fancy math and uses a named pipe to push data to the child process. The child does some more fancy math. When I uses a keyword, the child

问题 I need help returning a "status code" from my child program back to the parent, where it will check the status code, print code, and exit the parent. This is for a class project, so I will put some relevant code here, but I don't to post the entire project for obvious reasons. I have forked and created the child process through exec. The parent does some fancy math and uses a named pipe to push data to the child process. The child does some more fancy math. When I uses a keyword, the child