c - 为什么我的 fifo 读取中间有奇怪字符的返回字符串？

Question

我正在尝试通过命名管道将日志记录语句传递给守护进程。这些语句包含时间戳、发件人和消息。这些消息是按预期创建的，但是当我从管道的另一端读取它们时，它们有时会在字符串中间出现奇怪的字符，例如 Úèþ。我尝试将 '\0' 附加到每个日志记录语句的末尾，但它没有任何效果。下面是我的管道创建和读取部分的代码:

char * fdfifo = "./fifo/myfifo";
    mkfifo(fdfifo, 0666);
    int fd = open(fdfifo,O_RDONLY);
    struct timeval timeout;
    timeout.tv_sec = 5;
    timeout.tv_usec = 0;
    logger(getpid(), pthread_self(), "logger started");
    while(1 && keepRunning){
        fd_set fds;
        FD_ZERO(&fds);
        FD_SET(fd, &fds);
        if(select(fd + 1, &fds, NULL, NULL, &timeout)<=0){
            logger(getpid(), pthread_self(), "stopping logger");
            close(fd);
            exit(EXIT_SUCCESS);
            break;
        }
        else{
            pthread_mutex_lock(&lock2);
            FILE *f = fopen("./log/log.log", "a");
            char concat_str[200];
            read(fd, concat_str, 200);
            fprintf(f, "%s\n", concat_str);
            fclose(f);
            pthread_mutex_unlock(&lock2);
        }
    }

这是我写入管道的部分:

int startLoggerEnd(){
    readfifo = "./fifo/myfifo";
    mkfifo(readfifo, 0666);
    writedesc = open(readfifo,O_WRONLY);
    sleep(2);
    return 0;
}

int logger(pid_t pid, pthread_t tid, char *message){
    char tmp[100];
    char buff[20];
    char msg[200];
    struct tm *sTm;
    time_t now = time (0);
    sTm = gmtime (&now);
    strftime (buff, sizeof(buff), "%Y-%m-%d %H:%M:%S", sTm);
    sprintf(msg,"%s %s %d %s %d %s %s\n", get_timestamp(tmp), "process:", pid,
            "thread:",(unsigned) tid, "||", message);
    write(writedesc, msg, strlen(msg));
    return 0;
}

还有日志文件末尾的几行:

13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
 process: 14736 thread: 127881216 || moi
13:29:41:729 process: 14736 thread: 127881216 || moi
13:29:

Answer 1

您当前正在显示分配的内存片 (str2)。

但是，您不能确保您请求的内存部分是空的。

它可能包含之前操作的字节，导致显示不佳。

确保不显示先前字节的正确方法是在打印之前清理内存。

char *str2 = calloc(strlen(msg) + 1, sizeof(char));
strcpy(str2, msg);
str2[strlen(msg)] = '\0'; // index start at 0, strlen start at 1
write(fd, str2, strlen(str2));
close(fd);

calloc 将在返回给您之前清理分配的内存。

此外，请注意这段代码存在严重的内存泄漏问题，您甚至没有释放已分配的 str2。