fork

问题 I've recently learned how to do the whole fork/exec/wait thing and ended up writing some code that looked like this stripped down: #include <stdio.h> #include <stdlib.h> #include <unistd.h> int main() { pid_t x = fork(); if (x == 0) { execlp("sqlite3", "sqlite3"); printf("exec failed\n"); } else { wait(NULL); printf("Hi\n"); } } This works out pretty well, and actually ends up opening the sqlite3 shell, but there's one problem. If you Ctrl + C out of the sqlite3 shell, then it also terminates

问题 I am having a difficult time understanding what the fork() command does under different scenarios. Here is some sample code from my book: int main() { int a = 12; int b = 9; int fid = fork(); if (fid == 0) { a++; } else { wait(NULL); b = b - 5; } printf("program exit. a = %d, b = %d\n", a, b); return 0; } Can someone walk me through what the fork() command is doing in this case and perhaps give some more examples to clarify? 回答1: [main] a = 12 b = 9 fork() | | +--------------+--------------+

问题 I know there's another thread with the same name, but this is actually a different question. When a process forks multiple times, does the parent finish executing before the children? Vice versa? Concurrently? Here's an example. Lets say I have a for loop that forks 1 parent process into 4 children. At the end of that for loop, I want the parent process to feed some data to the children via pipes. The data is written to each child process' respective stdin. Will the parent send the data first

问题 OK I have a program that creates two pipes -> forks -> the child's stdin and stdout are redirected to one end of each pipe -> the parent is connected to the other ends of the pipes and tries to read the stream associated with the child's output and print it to the screen (and I will also make it write to the input of the child eventually). The problem is, when the parent tries to fgets the child's output stream, it just stalls and waits until the child dies to fgets and then print the output.

问题 Calling tzset() after forking appears to be very slow. I only see the slowness if I first call tzset() in the parent process before forking. My TZ environment variable is not set. I dtruss 'd my test program and it revealed the child process reads /etc/localtime for every tzset() invocation, while the parent process only reads it once. This file access seems to be the source of the slowness, but I wasn't able to determine why it's accessing it every time in the child process. Here is my test

问题 I have situation where one parent process may spawn many child processes. What I want to achieve is that if parent process is killed or if it exits, then all it's children should terminate together with parent. In the post (link below) I have found suggestion to archive this by making parent process a group leader. If I understand it right this is also the main purpose of process groups. Am I right? Post also mentions prctl(PR_SET_PDEATHSIG, SIGHUP); and some other methods, but they are ether

问题 I'm trying to make a homework assignment where I have to use fork() but I don't know why I can't stop my forks after running them through my for loop: #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/types.h> #include <sys/wait.h> int main(int argc, char *argv[]){ int limit = argc/2; if(argc%2 == 0){ perror("the number of arguments given must pe even!"); exit(1); } int i; for(i=0; i<=limit; i++){ if(fork()==-1){ perror("childes couldn't be created\n"); exit(1); } if

问题 I'm supposed to be getting comfortable with fork, and I saw an exercise that said to use a fork call to search an array indexed from 0 to 15. We're to assume that each process can only do two things...(1) is to check to see if an array is length 1, and (2) compare a single element of an array to the number were searching for. Basically i pass it a number, and its supposed to do a finite number of forks and return the index of that number. Here's my code.. #define MAXINDEX 16 int forkSearch

问题 I got a question to solve but it is giving me errors: 2009-EE-182-Part2.c: In function ‘main’: 2009-EE-182-Part2.c:35:13: error: expected identifier or ‘(’ before ‘->’ token 2009-EE-182-Part2.c:40:22: error: expected identifier or ‘(’ before ‘->’ token 2009-EE-182-Part2.c:41:14: error: expected identifier or ‘(’ before ‘->’ token 2009-EE-182-Part2.c:42:22: error: expected expression before ‘shared_data’ 2009-EE-182-Part2.c:44:15: error: expected identifier or ‘(’ before ‘->’ token 2009-EE-182

问题 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 回答1: You need to add a remote repo ' upstream ' in the local repo (which has for origin your fork) (git remote man page) git