fork

问题 C beginner here. I'm trying to read from my reducer_pipes in the fork_reducer method, but when I call read , nothing under the read gets executed. If I don't call read it does get executed. The read method does not appear to be printing any error messages. C Code #include <sys/wait.h> #include <stdbool.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <time.h> #include <errno.h> #define BUFFER_SIZE 1024 #define ALPHA_OFFSET 97 #define LETTERS 26 const

问题 My Windows 7 was upgraded to Windows 10 a week ago. Before the upgrade, my NetBeans IDE 8.0.2 with C/C++ plugin worked fine with C++ programs. However, after the Windows 10 upgrade, it cannot build/make C++ programs any more, with the error message below. Note that the Java plugin still works fine, and the C++ editor part is still OK too. The C/C++ Tool Collection is 64-bit Cygwin. Any clue on what caused this specifically, and any solution on fixing this? ===== Complete Error Message Below:

问题 Program runs once and it both throws data to the pipe and gets it out in the same condition that should be mutually exclusive (in if and else). What I don't get here? How does that work? I have no experience with this kind of programming. #include <sys/types.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> Read characters from the pipe and echo them to stdout. void read_from_pipe (int file) { FILE *stream; int c; stream = fdopen (file, "r"); while ((c = fgetc (stream)) != EOF)

问题 Attempting to write a message to anonymous shared memory with a child process, terminate it. Then have the message read by the parent. I have seen examples for mapping input & output files using file descriptors obtained through read & write calls. But do not know how to approach this correctly. int main(void) { char *shared; int status; pid_t child; shared = mmap(0, sizeof(int) , PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0); if (shared == MAP_FAILED) { perror("mmap"); return 1; }

问题 May be it look childish for most of you but I am unable to understand this small piece of code. #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> int main(int argc, char** argv) { int i, pid; pid = fork(); printf("Forking the pid: %d\n",pid); for(i =0; i<5; i++) printf("%d %d\n", i,getpid()); if(pid) wait(NULL); return (0); } Out put of this program is Forking the pid: 2223 0 2221 1 2221 2 2221 3 2221 4 2221 Forking the pid: 0 0 2223 1

问题 This question already has answers here : Closed 6 years ago . Possible Duplicate: fork() and output by running: #include<stdio.h> int main() { fork(); printf("b"); if (fork() == 0) { write(1, "a", 1); }else{ write(1, "c", 1); } return 0; } I got cbcabbab , could someone explain the output to me? And if possible, is there a tool to see the running procedure step by step? 回答1: Try running it again, you'll probably get a different output. As for a tool to see the procedure step by step, I think

问题 I've been asked to develop the consumer (client) side to a producer (server), where the producer creates processes, waits until the consumer has read shared memory and deleted processes, then passes control back to the producer for the killing of processes and the shutting down of the shared memory block. I've researched the difference between sleep and wait, and realise that as soon as fork() is called, the child process begins running. The below code is after the creation of processes and

问题 I have forked many child processes and assigned priority and core to each of them. Porcess A executes at period of 3 sec and process B at a period of 6 sec. I want them to execute in such a way that the higher priority processes should preempt lower priority ones only at predefined points and tried to acheive it with semaphores. I have used this same code snippets within the 2 processes with different array values in both. 'bubblesort_desc()' sorts the array in descending order and prints it.

问题 If I have a process which creates N threads; namely T1 .... Tn. Assume that N threads are using a lock L to synchronize among themselves. If this process calls fork() The new child process created has N threads or just 1 thread ? From this question, looks like its just 1 thread The lock L is copied to new memory (physical) location with the same value, right ? If answer to question (1) is that only 1 thread gets copied, what happens in new process if T1 had locked L and fork() is called from

问题 I'm confused. Supposedly, basing on man, and many other sources, like this: Return code when OS kills your process wait(&status) should make it possible for me to get the exit status or return value of a child process? Those 2 snippets of code, should allow me to see the exit value of it's child, and then print it. child process function: int childFunction(char in[],char logPath[]){ FILE *logFile= fopen( logPath, "a" ); if(logFile==NULL) return 1; int c=system(in); fclose(logFile); return(c);