fork | 易学教程

How can I manage a fork pool in Perl?

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问题 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? 回答1: 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

Applications of fork system call

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问题 fork is used to create a copy of process from which its called. This is typically followed by calls to exec family of functions. Are there any usages of fork other than this? I can think of one. Doing IPC with pipe functions. 回答1: Yes of course. It's quite common to start a process, do some data initialization and then spawn multiple workers. They all have the same data in their address space and it's Copy On Write. Another common thing is to have the main process listen to a TCP socket and

Maven Surefire: Unable to fork parallel test execution

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问题 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

socket() returns 0 in C client server application

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问题 I'm working on an application that contains several server sockets that each run in a unique thread. An external utility (script) is called by one of the threads. This script calls a utility (client) that sends a message to one of the server sockets. Initially, I was using system() to execute this external script, but we couldn't use that because we had to make sure the server sockets were closed in the child that was forked to execute the external script. I now call fork() and execvp()

Output from fork() in c

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I recently ran into this piece of code, and don't fully understand it. What circumstances would cause pid == 0? Why does wait(NULL) cause the program to go into the if(pid == 0) Basically I don't fully understand the output below. Any help would be appreciated. Thank you. Code: #include <stdio.h> #include <stdlib.h> #include <unistd.h> // standard POSIX header file #include <sys/wait.h> // POSIX header file for 'wait' function int main(void) { int i = -1; int pid; pid = getpid(); fprintf(stdout, "parent pid = %d\n", pid); pid = fork(); if (pid == 0) { for (i = 0; i < 10; ++i) { fprintf(stdout,

Errno::ENOMEM: Cannot allocate memory - cat

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问题 I have a job running on production which process xml files. xml files counts around 4k and of size 8 to 9 GB all together. After processing we get CSV files as output. I've a cat command which will merge all CSV files to a single file I'm getting: Errno::ENOMEM: Cannot allocate memory on cat (Backtick) command. Below are few details: System Memory - 4 GB Swap - 2 GB Ruby : 1.9.3p286 Files are processed using nokogiri and saxbuilder-0.0.8 . Here, there is a block of code which will process 4

fork() and exec() Two Child Processes

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I am calling fork() twice to create two child processes. I want child process A to do an exec() call and child process B to also do an exec() call. The problem I am having with the given code is that after the first exec() from child process A, the next fork() does not seem to occur and the program exits. I think that it has to do with how exec() overlays the parent process. What I want to accomplish is to call exec() from each of the child processes created by fork(). #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> #include <sys/wait.h> #include <stdlib.h> #include <unistd.h>

Github Fork 缎带.html

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/*--> */ /*--> */ <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title></title> <style> .ribbon { background-color: #a00; overflow: hidden; /* top left corner */ position: absolute; left: -3em; top: 2.5em; /* 45 deg ccw rotation */ -moz-transform: rotate(-45deg); -webkit-transform: rotate(-45deg); /* shadow */ -moz-box-shadow: 0 0 1em #888; -webkit-box-shadow: 0 0 1em #888; } .ribbon a { border: 1px solid #faa; color: #fff; display: block; font: bold 81.25% 'Helvetiva Neue', Helvetica, Arial, sans-serif; margin: 0.05em 0 0.075em 0; padding: 0.5em 3.5em; text-align: center; text

github fork confusion

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I followed this https://help.github.com/articles/fork-a-repo post to clone a repository locally. After doing that another developer created a branch to the main repository and added some features to that branch. My question is How do I get that branch into my fork. Can I get that missing branch again to my local using git pull upstream/missing_branch command? Thank you VonC You need to add a remote repo ' upstream ' in the local repo (which has for origin your fork) ( git remote man page ) git remote add upstream url://upstream/repo The OP opensourcelover mentions seeing this : git remote -v,

process from pcntl_fork not terminating

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I am running a web service which involved with daemons by php+apache2. So I tried pcntl_fork function. But there is a question that the child process are not terminating even I used exit(0) in the child process's code which result in a lot of apache2 processes. I'm wondering if there is a way to shutdown those useless apache2 processes? PS: because I'm not very aware of the mechanism of signal, so I tried to make daemon by a single call to a agent script which will exit as soon as the child is created. switch ($_GET['action']){ case "new": $pid = pcntl_fork(); switch ($pid){ case -1: echo