fork

问题 I'm having issues with my client side implementation of client server chat program where multiple clients connect. The issue is that i'm coming across is that how exactly should i be sending (chat message to another client) and receiving (chat message from another client) at the same time? What's happening is that i'm always sending data and never reading. Do i need to fork and have one read and the other send? here is the relevant code client side while(1) { fd_set rfds, wfds; FD_ZERO(&rfds)

问题 This code is supposed to print "Output from 'ls -l':" and append the result of 'ls -l', but it doesn't... Does anyone has a clue whats wrong with this? #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> void readStringFromFile (int file, char * readbuffer) { int nbytes = read(file, readbuffer, sizeof(readbuffer)); readbuffer[nbytes] = 0; } int main(int argc, char const *argv[]) { int fd[2]; pipe(fd); if (fork()==0)//child process { close(fd[0]); dup2(fd[1],1);

问题 I am trying to figure out how many processes are created with the following C code: int main () { fork(); if (fork()) { fork(); } fork(); return 0; } There are a couple of things I am confused about: Each time fork() is called, does the child start from the start of the code, or does it start where the current fork() created it from? For instance, if line 3's first fork is called, will I start the child at line 4, or line 1? I believe this is a stupid question, b/c it would create an infinite

问题 I am trying to run a simple program in cygwin that includes fork and wait. I thought it would be very easy to compile but I am having problems. #include <stdio.h> #include <unistd.h> void testFork(){} int main(int argc,char* argv[]){ if (fork()==0) {testFork();return 0;} while (wait() == -1); return 0; } Compiled using: gcc -Wall -Wextra -o test.o test I get the following error: C:\Users\Aaron\AppData\Local\Temp\ccgh3MfS.o:ostest.c:(.text+0x11): undefined reference to `fork' C:\Users\Aaron

问题 I am trying to to fork my c++ program and direct the parents output into the childs input, I am using pipe() and fork(). In the directory of the program there is a file called input.txt. Unfortunately the only output I get is "wc: stdin: read: Bad file descriptor". Does anyone know why this is? If so what am I doing wrong? Thanks #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/wait.h> #include <errno.h> #include <string.h> #include <iostream> #include<sys/types.h>

问题 I am new in C. I am trying to make a shell - like program. I am currently making a signal handler, which means, when the process is running and somebody pressed ctrl + Z the process should pause and go to background while shell has to continue. The problem here is: parent process is making wait(NULL) , but child is not ending the program so basically parent waits the child which is not ending the program yet. How to make it so that parent continues to work foreground. (you can see my code How

问题 I would like to use IPC::Run to communicate with child via child's STDIN, STDOUT and STDERR (start, pump, finish). It seems to work. I would like to know how to detect premature child exit (e.g. caused by errors) pipes closed by the child 回答1: The pump throws a die on errors, or writes its message to STDERR if " called after all harnessed activities have completed ." See right before ROUTINES section and pump itself. The second case can come about if the child exited. So wrap the pump call in

问题 I have the following function which execute command via fork and execvp. my script that I launch in fork is listening for input data. How I can send data to myscript? int external_command() { int pfds[2]; if (pipe(pfds) < 0) return -1; if ((uproc.pid = fork()) == -1) return -1; if (uproc.pid == 0) { /* child */ const char *argv[4]; int i = 0; argv[i++] = "/bin/sh"; argv[i++] = "myscript.sh"; argv[i++] = NULL; close(pfds[0]); dup2(pfds[1], 1); close(pfds[1]); execvp(argv[0], (char **) argv);

问题 I work on a system in which swap is disabled and memory overcommit is disabled. Lets say my process consumes 100 MB memory currently and the system free memory is less than 100 MB. If I do a fork() will it fail because kernel tries to allocate 100 MB for the child process as well ? I have read that Linux uses copy-on-write when forking, so child & parent share all the pages. So I guess fork should succeed ? Assuming fork succeeds, lets say I have few lines of code in the child process before

问题 I'm using Grails 2.3.5 and I need to pass an option to the forked JVM. I've tried doing this by setting the JAVA_OPTS environment variable, but that simply gets ignored by the forked JVM. How can I go about passing the forked JVM an option? I've found this: http://jira.grails.org/browse/MAVEN-177?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel but that's if you're using the Maven plugin I believe. I'm looking for the equivalent but without having to get Maven plugin involved