fork

My issue is this. I am forking a process so that I can speed up access time to files on disk. I store any data from these files in a tmp file on local desk. ideally, after all processes have finished, I need to access that tmp file and get that data into an array. I then unlink the tmp file as it is no longer needed. My problem is that it would seem that pcntl_wait() does not acutally wait until all child processes are done before moving on to the final set of operations. So I end up unlinking that file before some random process can finish up. I can't seem to find a solid way to wait for all

Consider the following script in which I test two ways of performing some calculations on generators obtained by itertools.tee : #!/usr/bin/env python3 from sys import argv from itertools import tee from multiprocessing import Process def my_generator(): for i in range(5): print(i) yield i def double(x): return 2 * x def compute_double_sum(iterable): s = sum(map(double, iterable)) print(s) def square(x): return x * x def compute_square_sum(iterable): s = sum(map(square, iterable)) print(s) g1, g2 = tee(my_generator(), 2) try: processing_type = argv[1] except IndexError: processing_type = "no

I read that the new process created using vfork() system call executes as a thread in the parent's address space and until the child thread doesnot calls exit() or exec() system call, the parent is blocked. So I wrote a program using vfork() system call #include <stdio.h> #include <unistd.h> int main() { pid_t pid; printf("Parent\n"); pid = vfork(); if(pid==0) { printf("Child\n"); } return 0; } I got the output as follows: Parent Child Parent Child Parent Child .... .... .... I was assuming that the return statement must be calling the exit() system call internally so I was expecting the

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? kbenson Forking (or threading) is what you want, but you should look at CPAN for modules that will provide most of what you need to prevent you from reinventing the wheel and going through the learning pains of what you need to do. For example, Parallel:

进程的定义 进程是指一个具有一定独立功能的程序在一个数据集合上的一次动态执行过程 源代码在经过编译链接之后生成了可执行文件，再由操作系统进行加载并且进行一些堆栈的分配才是进程 进程控制块 操作系统管理控制进程运行所用的信息集合 操作系统用PCB来描述进程的基本情况以及运行变化的过程 PCB是进程存在的唯一标志 每个进程都在操作系统中有一个对应的PCB 进程控制块主要包含的就是进程的标识信息，处理机现场保存和进程控制信息 控制信息 ： 调度和状态信息 进程间通信信息 存储管理信息 进程所用资源 有关数据结构连接信息 进程的生命周期 进程创建 用户请求创建一个新进程，正在运行的进程执行了创建进程的系统调用，并且加入到就绪队列 进程执行 内核对就绪队列进行调度，到执行该进程 进程等待 运行中的进程可能会进入阻塞状态，比如进行IO的等待或者需要的数据没有到达 进程抢占 运行中的进程可能时间片被用完或者高优先级进程被唤醒导致了进程被抢占进入阻塞状态 进程唤醒 被阻塞需要的资源可以被满足就可能被唤醒进入就绪队列 进程结束 进程完成任务或者被迫结束 线程的定义 线程是进程的一部分，描述指令流执行状态。它是进程中的指令执行流的最小单元，是CPU调度的基本单位。 进程作为资源分配角色 进程由一组相关资源构成，包括地址空间（代码段、数据段）、打开的文件等各种资源 线程作为处理机调度角色

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? You mean that's a process tree and in the bubbles is the value of x ? Then no, that's not correct. When a child is spawned, it gets an exact copy of the parent...

,_,( ){ ,_,| ,_,&};,_, I am not sure what it means... Looks like a bash command but it might be s bash shell directive or something would appreciate if someone can help understand this. It killed my bash when I ran it. It's a fork bomb ; it will spawn a (potentially) infinite number of processes, until your system runs out of resources (and usually becomes inoperable). It defines the function named ,_, , which runs itself (recursion), and piping the output to itself. The last ,_, is needed to start off the thing. Formatted, and with ,_, replaced by fun , it looks like: fun() { fun | fun & };

https://docs.python.org/zh-cn/3/library/multiprocessing.html 在 3.8 版更改: 对于 macOS， spawn 启动方式是默认方式。 因为 fork 可能导致subprocess崩溃，被认为是不安全的，查看 bpo-33725 。 来源： https://www.cnblogs.com/yuanjiangw/p/11904721.html

As the parent process is using huge mount of memory, fork may fail with errno of ENOMEM under some configuration of kernel overcommit policy. Even though the child process may only exec low memory-consuming program like ls. To clarify the problem, when /proc/sys/vm/overcommit_memory is configured to be 2, allocation of (virtual) memory is limited to SWAP + MEMORY * ration(default to 50%) . When a process forks, virtual memory is not copied thanks to COW. But the kernel still need to allocate virtual memory space. As an analogy, fork is like malloc(virtual memory space size) which will not

using Maven surefire, I'm unable to fork parallel test execution. That is, each of my test cases hs to run in a serapate JVM, hence the forking. In addition, I want my test cases to run in parallel. the first part is working without problem: I'm able to run each test case in its own JVM. the second part, however is still a challene for me. I haven't managed to get the paralle execution of test cases working. Here is how my plugin declaration look like: <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <version>2.5</version> <configuration>