fork | 易学教程

Using fork() in simplest form need to hit enter to finish execution

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问题 I want to run some simple example to find out how fork() system call work. Its work but need to hit enter to exit the program after printing child process . #include <stdio.h> #include <unistd.h> int main() { pid_t pid; pid = fork(); if(pid == 0){ printf("child process\n"); } else{ printf("parent process\n"); } return 0; } compile, run & output ss@ss:~$ gcc dd.c -o dd ss@ss:~$ ./dd parent process ss@ss:~$ child process after print child process on screen program need to hit enter key to

How to create two child process executing parallel from a single parent process in C++?

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问题 Hi I'm working gin C++ on Linux platform. I have a parent process. i need to create two child process from this parent which will be execute in parallel for some time. While Parent process is waiting for both the process to complete and then it finishes its execution. any suggestion ? 回答1: use fork() and exec family of functions to start child processes. parent process can call waitpid till child process exists. exec link: http://linux.about.com/library/cmd/blcmdl3_execvp.htm 回答2: Spawn the

How to find the call to fork in my python program

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问题 Some module in my python program is calling fork(), and my mpi environment is unhappy with this: A process has executed an operation involving a call to the "fork()" system call to create a child process. Open MPI is currently operating in a condition that could result in memory corruption or other system errors; your job may hang, crash, or produce silent data corruption. The use of fork() (or system() or other calls that create child processes) is strongly discouraged. The process that

Why does my GitHub pull request have two commits?

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问题 I've forked a project on GIT, and started contributing. From what I've understood, that project has a pending pull request at the time I cloned the project, and later that commit of a 3rd person was refused by the project owner. I've done my change (adding a single new file), and I wanted to push it to the master branch of the project. So I've pushed it to my github master branch, and then I wanted to make a pull request. In case I'm not clear, I've done this: Clone the project add a file &

PHP FPM源代码反刍品味之三: 多进程模型

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 本文开始会涉及写源代码, FPM源代码目录位于PHP源代码目录下的sapi/fpm FPM多进程轮廓： FPM大致的多进程模型就是：一个master进程,多个worker进程. master进程负责管理调度，worker进程负责处理客户端(nginx)的请求. master负责创建并监听(listen)网络连接，worker负责接受(accept)网络连接. 对于一个工作池，只有一个监听socket, 多个worker共用一个监听socket. master进程与worker进程之间，通过信号(signals)和管道(pipe)通信． FPM支持多个工作池(worker pool), FPM的工作池可以简单的理解为监听多个网络的多个FPM实例，只不过多个池都由一个master进程管理．这里只考虑一个工作池的情况，理解了一个工作池，多个工作池也容易. fork()函数 Unix类操作系统通过fork调用新建子进程． int pid = fork(); fork函数，可以简单的理解为克隆一份进程，包含全局变量的复制．父子进程几乎一模一样，是两个独立的进程，两个进程使用同一份代码．在fork之前运行的代码也一样．两个进程之所以拥有不同的功能．主要就是在fork之后，父进程返回的子进程pid(大于零)

Forking a new process in C++ and executing a .jar file

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问题 I am attempting to write a program that will read the output from a java .jar file and also give it input from time to time. Basically I am hoping to make a program that will execute certain functions when certain output is encountered. The .jar file wasn't created by me, and I don't have the source code, so I have to use it as-is. After doing some research I decided using fork() and execl() in conjunction with pipes was the method I would need to use and I created a small program that

How to avoid read() from hanging in the following situation?

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问题 I have some code that forks a third-party application and redirects its standard output to the parent process, roughly as follows (no error handling here for brevity): char* args[] = {"/path/to/3rd/party/binary", "with", "args", NULL}; int fds[2]; pipe2(fds, O_CLOEXEC); pid_t pid = fork(); if (pid == 0) { dup2(fds[1], STDOUT_FILENO); execvp(args[0], args); _exit(1); } else { close(fds[1]); char buf[1024]; int bytes_read; while ((bytes_read = read(fds[0], buf, sizeof buf - 1)) > 0) { buf[bytes

（004）linux系统编程

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文章目录 fork 函数 gdb调试多进程程序子进程状态（孤儿与僵尸）子进程回收 exec 函数族 fork 函数 fork 函数用于创建一个进程（创建当前调用此函数的子进程）父进程的fork返回子进程ID ；而子进程的fork返回 0，表示进程创建成功 getpid函数返回调用此函数的进程ID；getppid函数返回调用此函数的父进程ID getuid函数返回当前进程的实际用户ID；geteuid函数返回当前进程的有效用户ID 在fork之后，父子进程有相同的权利去抢占CPU，并不意味着父进程的优先级一定会比子进程的高，取决于内核所使用的调度算法 fork函数遵循 “ 读时共享，写时复制 ” 的原则：如果fork后的代码只有读操作，那么共享同一块物理地址；否则复制一份循环创建多个进程示例：用 for() { fork(); } 循环调用fork函数会创建 2 n - 1 个子进程。正确的方法应该如下： # include <stdlib.h> # include <unistd.h> # include <stdio.h> int main ( ) { pid_t pid ; int i ; for ( i = 0 ; i < 5 ; ++ i ) { pid = fork ( ) ; if ( pid == - 1 ) { perror ( "fork

Create independent process in Linux

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问题 I'm looking to implement a function similar to CreateProcess but on Linux. I did a lot of research and found the "Fork off and die" approach which uses a double fork to run the child under init. That is, allow the child to operate independent of the parent. Because the parent needs to return information about the newly created child process (i.e. pid, name, etc.) I need to know if I'm running into a race condition in my code. Currently, I fork and retrieve the second fork's pid via pipes then

Referencing pointers after a fork() call in C

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问题 So, I've got a function that loads up a char** variable with some string data. My goal is to fork the process, and print some of that data in the child, and some from the parent. However, I'm unable to reference the pointer after the fork() call. I thought that fork() made a copy of the entire address space of the parent process, which seems that it would include the various stack pointers... Essentially, my code currently looks like this: load_data(char **data); char** data; load_data(data);