我的程序出现问题我想让run_uptime函数每隔5秒向stdout显示正常运行时间函数的输出。但是，我不知道我在代码中做错了什么，我查看了与exec（）和fork（）相关的各种其他问题，但我似乎仍无法找到解决方案。另一件事是如何在没有switch语句的情况下重写fork调用，但这更多是一个美学原因，但我仍然想知道如何去做。我很感激任何帮助。请解释原因，因为我是新手。
问题陈述，程序应该做什么：
您应创建一个执行以下操作的程序：
o启动时，读取用户希望程序运行的总运行时间（以秒为单位）。如果用户不包括启动程序的时间，则将使用默认值10秒（即，rohan＆gt; a3 30导致程序运行30秒，rohan＆gt; a3将运行程序10秒）。
o程序应创建三个子进程，然后忙等待直到所有子进程完成然后退出。
o第一个子进程应实现一个时钟，每秒打印一小时，分钟和秒（在人类可读的本地时间）
o第二个子进程应每5秒运行一次正常运行时间（/ usr / bin / uptime）
o第三个子进程应实现倒数计时器，打印剩余的分钟和秒数，每秒一次，直到达到00:00。
o第三个子进程在到达00:00时，应通知（信号，管道或......等，您选择的IPC机制）第一个和第二个子进程'（即它的兄弟进程）他们终止然后终止自己。
o所有子进程终止后，父进程应打印一条友好消息，然后退出。
这是我的代码，它编译但我需要一个不同的输出。
/* Include Files */
#include <stdio.h>
#include <time.h> /* for local time functions */
#include <unistd.h> /* for fork */
#include <string.h>
#include <stdlib.h>
#include <sys/wait.h> /* for wait function */
#include <sys/types.h> /* for pid_t */
/* remember 0 means program finished correctly, by unix convention */
/* Definitions */
#define TIME_QUANTUM 5 //Default time for program to run!
/* Functions */
void system_clock(void); //function to display human readable time.
void time_to_kill(int timequota); //prints out the time in a countdown fashion, till program ends.
void run_uptime(void);
/* Variables */
int procpipe1[2]; //Allocate Pipe Set 1
int procpipe2[2]; //Allocate Pipe Set 2
char bufkill[12]; //Buffer to hold kill signal, to tell other processes to end.
int main(int argc, const char * argv[])
{
int time=TIME_QUANTUM;
if(argc==2)
{
time=atoi(argv[1]); //looking to see if user wants a custom running time.
}
//Creating pipes before creating child processes, so they could communicate.
pipe(procpipe1);
pipe(procpipe2);
printf("Pipes opened, now creating child process!\n");
//Create Child Processes and run associated functions in them.
//Creating the the 1st child process!
switch (fork())
{
case -1:
printf("Error: couldn't create 1st Child!\n");
exit(1);
case 0: //If no error in creating child process then create process!
printf("\nChild 1 process: time_to_kill executing...\n");
system_clock();
exit(1);
default:
break;
}
//Creating the 2nd child process!
switch (fork())
{
case -1:
printf("Error: couldn't create 3rd Child!\n");
case 0: //If no error in creating child process then create process!
printf("\nChild 2 process: time_to_kill executing...\n");
run_uptime();
exit(1);
default:
break;
}
//Creating the 3rd child process!
switch (fork())
{
case -1:
printf("Error: couldn't create 2nd Child!\n");
exit(1);
case 0: //If no error in creating child process then create process!
printf("\nChild 3 process: time_to_kill executing...\n");
time_to_kill(time);
exit(1);
default:
break;
}
printf("Parent closing pipes\n");
//Need to close the pipes after using them, close communications between processes.
//pipe close error checking
close(procpipe1[0]);
close(procpipe1[1]);
close(procpipe2[0]);
close(procpipe1[1]);
printf("Parent waiting for children completion...\n");
//Wait for child processes to end before ending Main, the overall process
//that spawned the child processes.
wait(NULL);
wait(NULL);
wait(NULL);
printf("Time to print out a Friendly Message!\n");
printf("Parent process finishing, bye!\n");
exit(EXIT_SUCCESS);
}//end main
//This is the 1st Child Process
void system_clock(void)
{
/* variable of system_clock()*/
//temp buffer to get termination string
char str1[12];
time_t now;
struct tm *lcltime;
strcpy(str1, "time to die"); //store this string into str1 local variable
close(procpipe1[0]);
close(procpipe1[1]);
close(procpipe2[1]);
//show current time
for(;;)
{
now = time ( NULL );
lcltime = localtime ( &now );
//read message from child 2 process
int status = read(procpipe2[0], bufkill, 12);
if ((strcmp(str1, bufkill)) != 0)
{
//printf("Read status: %d, Buffer= %s\n", status, bufkill);
printf ("The time is %d:%d:%d\n", lcltime->tm_hour, lcltime->tm_min, lcltime->tm_sec );
//show ever second
sleep(1);
}
//if end signal came in
//if(ret == 0)
if ((strcmp(str1, bufkill)) == 0)
{
//close reading end
close(procpipe2[0]);
//return back to parent
printf("Child 1 process: system_clock ending...\n");
exit(1);
}
}
}//end system_clock
//This is the 2nd Child Process
void run_uptime()
{
// variable of run_uptime
//temp buffer to get termination string
char str1[12];
strcpy(str1, "time to die"); //store this string into str1 local variable
close(procpipe1[0]);
close(procpipe1[1]);
close(procpipe2[1]);
for(;;)
{
//read message from child 2 process
int status = read(procpipe2[0], bufkill, 12);
if ((strcmp(str1, bufkill)) != 0)
{
//printf("Read status: %d, Buffer= %s\n", status, bufkill);
execl("/usr/bin/uptime","uptime",NULL);
//show ever 5 seconds
sleep(1);
}
//if end signal came in
if ((strcmp(str1, bufkill)) == 0)
{
//close reading end of pipe.
close(procpipe2[0]);
//return back to parent
printf("Child 2 process: run_uptime ending...\n");
exit(1);
}
}
}//end run_uptime
//This is the 3rd Child Process
void time_to_kill(int timequota) //This process signals the other processes to stop.
{
/* Need to change this signal */
//string signal to end process
strcpy(bufkill, "time to die");
//Pipes that aren't being used close them.
close(procpipe1[0]);
close(procpipe1[1]);
close(procpipe2[0]);
for( ;timequota>0; timequota--)
{
printf("Count Down: 00:0%d\n", timequota);
//send signal to child 1 process and child 2 process not to end
write(procpipe2[1], "not die yet",12); //write into pipe2 statement that doesn't signal stopping process.
//count down every second
sleep(1);
}
//send signal to child 1 process and child 2 process to be terminate itself.
write(procpipe2[1], bufkill, sizeof(bufkill)); //write into pipe2 the kill statement stored in bufkill
//close pipe 2 writing end
close(procpipe2[1]);
//back to main
printf("Count Down: 0\n");
printf("Child 3 process: time_to_kill ending...\n");
exit(1);
}//end time_to_kill