我正在通过编写一个简单程序来学习fork（）和管道。我成功返回了结果，但是结果之一重复了一次。我一直在尝试用代码来解决它，但无法正确完成。
睡眠时间就是模拟系统调整的时间。我一直试图将导航睡眠时间设置为介于0到6之间的随机秒数，但我无法设法做到这一点并打印出生成给报告的随机数。这是我愿意忍受的问题，但希望它能奏效。
当前代码：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <wait.h>
#include <time.h>
#define MAX 150
#define PipeStdIn 0 //UNIX StdIn
#define PipeStdOut 1 //UNIX StdOut
void lifeSupport();
void navigation();
int main()
{
const char *message = {"Calibrate Systems\n"};
int pipes[2], ret;
char buf[MAX + 1];
if(pipe(pipes) == 0)
{
if(fork() == 0)
{
ret = read(pipes[PipeStdIn], buf, MAX);
printf("Life Support receives instruction: %s\n", buf);
sleep(5);
sleep(4);
const char *breathGL = {"Breathing gas levels have been adjusted\nAdjustment time: 5 seconds\nLighting and temperature levels have been adjusted\nAdjustment time: 4 seconds\n"};
ret = write(pipes[PipeStdOut], breathGL, strlen(breathGL) + 1);
}
else
{
ret = write(pipes[PipeStdOut], message, strlen(message) + 1); //write
ret = wait(NULL);
ret = read(pipes[PipeStdIn], buf, MAX);
time_t now;
time(&now);
printf("Report received: %s\n", buf);
printf("Report time: %s\n", ctime(&now));
}
}
if(pipe(pipes) == 0)
{
if(fork() == 0)
{
ret = read(pipes[PipeStdIn], buf, MAX);
printf("Navigation receives instruction: %s\n", buf);
sleep(3);
const char *nav = {"Navigation system has been adjusted\nAdjustment time: 3 seconds\n"};
ret = write(pipes[PipeStdOut], nav, strlen(nav) + 1);
}
else
{
ret = write(pipes[PipeStdOut], message, strlen(message) + 1); //write
ret = wait(NULL);
ret = read(pipes[PipeStdIn], buf, MAX);
time_t now;
time(&now);
printf("Report received: %s\n", buf);
printf("Report time: %s\n", ctime(&now));
}
}
close(pipes[PipeStdIn]);
close(pipes[PipeStdOut]);
return 0;
}
预期结果：
Life Support receives instruction: Calibrate Systems
Report received: Breathing gas levels have been adjusted
Adjustment time: 5 seconds
Lighting and temperature levels have been adjusted
Adjustment time: 4 seconds
Report time: Tue Apr 28 08:48:49 2020
Navigation receives instruction: Calibrate Systems
Report received: Navigation system has been adjusted
Adjustment time: 3 seconds
Report time: Tue Apr 28 08:48:52 2020
当前结果：
Life Support receives instruction: Calibrate Systems
Navigation receives instruction: Calibrate Systems
Report received: Navigation system has been adjusted
Adjustment time: 3 seconds
Report time: Tue Apr 28 08:48:49 2020
Report received: Breathing gas levels have been adjusted
Adjustment time: 5 seconds
Lighting and temperture levels have been adjusted
Adjustment time: 4 seconds
Report time: Tue Apr 28 08:48:49 2020
Navigation receives instruction: Calibrate Systems
Report received: Navigation system has been adjusted
Adjustment time: 3 seconds
Report time: Tue Apr 28 08:48:52 2020
如果注释中的解释不清楚，则需要将完整的第二个if(fork() == 0) {...} else {...}移动到第一个else中，以防止父级和子级都执行该块。向上移动if(fork() == 0) {...} else {...}后，您的逻辑将类似于：
if(pipe(pipes) == 0)
{
if(fork() == 0)
{
ret = read(pipes[PipeStdIn], buf, MAX);
...
ret = write(pipes[PipeStdOut], breathGL, strlen(breathGL) + 1);
}
else
{
ret = write(pipes[PipeStdOut], message, strlen(message) + 1);
...
if(fork() == 0)
{
ret = read(pipes[PipeStdIn], buf, MAX);
...
const char *nav = "Navigation system has been adjusted\n"
"Adjustment time: 3 seconds\n";
ret = write(pipes[PipeStdOut], nav, strlen(nav) + 1);
}
else
{
ret = write(pipes[PipeStdOut], message, strlen(message) + 1);
...
// time_t now;
time(&now);
printf("Report received: %s\n", buf);
printf("Report time: %s\n", ctime(&now));
}
}
}
close(pipes[PipeStdIn]);
close(pipes[PipeStdOut]);
还请注意，C编译将在编译过程中将相邻的字符串连接为单个字符串，使您可以将长行分解为一系列双引号的字符串，例如，在编译时将它们连接在一起。
const char *breathGL = "Breathing gas levels have been adjusted\n"
"Adjustment time: 5 seconds\n"
"Lighting and temperature levels have been adjusted\n"
"Adjustment time: 4 seconds\n";
和
const char *nav = "Navigation system has been adjusted\n"
"Adjustment time: 3 seconds\n";
（（也请注意不包含{...}）
仔细检查，如果还有其他问题，请告诉我。