Question

我想从子进程向父进程发送数据。我做管道并尝试发送数据，它正在工作。但是如何看待这个子流程在父流程中完成了它的工作呢？

我的代码是：

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>

int main(int argc, char **argv){
    pid_t pid;
    int status;
    int i;
    int pipe[2];
    char buf[1];
    char  *envp[] = {NULL};
    char  *arg[] = {NULL, "2", NULL};
    int res;
    if(argc != 3){
        exit(EXIT_FAILURE);
    }
    if(pipe2(pipe, 0) == -1){
        printf("-1 : %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }
    arg[0] = argv[1];
    // for(i = 0; i < argc; i++){
    //  printf("argv[%d]: %s\n", i, argv[i]);
    // }
    pid = fork();
    if(pid == -1){
        printf("1 : %s", strerror(errno));
        exit(EXIT_FAILURE);
    }
    if(pid == 0){
        printf("child start\n");
        close(pipe[0]);
        dup2(pipe[1], 1);
        if(-1 == execvp(argv[1], arg)){
            printf("2 : %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }
        printf("child end\n");
        exit(0);
    } else {
        do{
            res = read(pipe[0], buf, 1);
            printf("read some info\n");
            if(res == -1){
                printf("%s\n", strerror(errno));
                break;
            } else if(res == 0) {
                printf("end\n");
                break;
            } else {
                if(*buf == EOF){
                    printf("EOF\n");
                }
                printf("char: %c\n", *buf);
            }
        } while(1);
        close(pipe[0]);
        printf("parent end\n");// in the parent
    }
    return 0;
}

第二个应用程序的代码是：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>


int main(int argc, char const *argv[])
{
    int i;
    int nmbr;
    for(i = 0; i < argc; i++){
        printf("g: argv[%d]: %s\n", i, argv[i]);
    }
    if(argc < 2){
        exit(EXIT_FAILURE);
    }

    printf("Hello from gen_test\n");
    nmbr = atoi(argv[1]);
    for(i = 0; i < nmbr; i++){
        printf("0");
        //sleep(1);
    }
    exit(EXIT_SUCCESS);
}

我将此应用用作

brainiac@brainiac-Latitude-7480:~/workspace/linux_fund$ ./solution ./a.out 2
child start
read some info
char: g
read some info
char: :
read some info
char:  
read some info
char: a
read some info
char: r
read some info
char: g
read some info
char: v
read some info
char: [
read some info
char: 0
read some info
char: ]
read some info
char: :
read some info
char:  
read some info
char: .
read some info
char: /
read some info
char: a
read some info
char: .
read some info
char: o
read some info
char: u
read some info
char: t
read some info
char: 

read some info
char: g
read some info
char: :
read some info
char:  
read some info
char: a
read some info
char: r
read some info
char: g
read some info
char: v
read some info
char: [
read some info
char: 1
read some info
char: ]
read some info
char: :
read some info
char:  
read some info
char: 2
read some info
char: 

read some info
char: H
read some info
char: e
read some info
char: l
read some info
char: l
read some info
char: o
read some info
char:  
read some info
char: f
read some info
char: r
read some info
char: o
read some info
char: m
read some info
char:  
read some info
char: g
read some info
char: e
read some info
char: n
read some info
char: _
read some info
char: t
read some info
char: e
read some info
char: s
read some info
char: t
read some info
char: 

read some info
char: 0
read some info
char: 0
^C

但是当子应用程序关闭时，我不能在父进程中和函数读取得到返回值零，我不知道为什么。需要帮助或任何建议。

无法捕捉关闭管道的时刻

0 个答案: