scanf会阻塞进程吗
时间: 2023-11-04 14:48:09 浏览: 40
是的,当调用 `scanf` 函数时,程序会等待用户输入数据,直到用户输入并按下回车键,否则程序会一直阻塞在 `scanf` 函数处,直到有数据输入。这种行为被称为阻塞式输入。在需要用户输入数据的时候,阻塞式输入是一种很常见的处理方式,但是在一些特殊情况下,如果程序需要等待用户输入的时间过长,可能会导致程序无响应或者卡死的现象。因此,在使用阻塞式输入时,需要注意控制等待时间,并考虑使用异步输入方式。
相关问题
1、模拟处理器管理功能 (1)模拟创建进程,并将进程插入就绪队列 (2)模拟进程调度算法,并将进程从就绪队列,转会到运行态 (3)模拟实现阻塞进程,并将进程插入某个资源的等待带队中。 (4)模拟实现唤醒进程,将进程从等待队列中出队,并将将该进程插入到就绪队列 (5)模拟实现进程的通信 备注:调度算法,可以在FIFO, SFJ,RR中选择一种或多种,也可只选择多级轮转调度算法实现调度
以下是一个简单的模拟处理器管理功能的C代码示例:
```c
#include <stdio.h>
#include <stdlib.h>
// 定义进程结构体
typedef struct {
int pid; // 进程ID
int runtime; // 运行时间
int state; // 进程状态,0表示就绪,1表示运行,2表示阻塞
} Process;
// 定义进程队列结构体
typedef struct {
Process** processes; // 进程数组指针
int front; // 队头指针
int rear; // 队尾指针
int capacity; // 队列容量
int size; // 队列当前大小
} ProcessQueue;
// 初始化进程队列
ProcessQueue* initQueue(int capacity) {
ProcessQueue* queue = (ProcessQueue*)malloc(sizeof(ProcessQueue));
queue->processes = (Process**)malloc(capacity * sizeof(Process*));
queue->front = 0;
queue->rear = -1;
queue->capacity = capacity;
queue->size = 0;
return queue;
}
// 判断队列是否为空
int isEmpty(ProcessQueue* queue) {
return queue->size == 0;
}
// 判断队列是否已满
int isFull(ProcessQueue* queue) {
return queue->size == queue->capacity;
}
// 入队操作
void enqueue(ProcessQueue* queue, Process* process) {
if (isFull(queue)) {
printf("队列已满,无法入队!\n");
return;
}
queue->rear = (queue->rear + 1) % queue->capacity;
queue->processes[queue->rear] = process;
queue->size++;
}
// 出队操作
Process* dequeue(ProcessQueue* queue) {
if (isEmpty(queue)) {
printf("队列为空,无法出队!\n");
return NULL;
}
Process* process = queue->processes[queue->front];
queue->front = (queue->front + 1) % queue->capacity;
queue->size--;
return process;
}
// 创建进程
Process* createProcess(int pid, int runtime) {
Process* process = (Process*)malloc(sizeof(Process));
process->pid = pid;
process->runtime = runtime;
process->state = 0; // 初始状态为就绪
return process;
}
// 进程调度函数
void scheduleProcess(ProcessQueue* readyQueue, ProcessQueue* runningQueue, int schedulingAlgorithm) {
switch (schedulingAlgorithm) {
case 1: // FIFO调度算法
if (!isEmpty(readyQueue)) {
Process* process = dequeue(readyQueue);
process->state = 1; // 将进程状态设置为运行
enqueue(runningQueue, process);
}
break;
case 2: // SJF调度算法
if (!isEmpty(readyQueue)) {
Process* shortestProcess = readyQueue->processes[readyQueue->front];
int shortestRuntime = shortestProcess->runtime;
// 寻找运行时间最短的进程
for (int i = readyQueue->front; i <= readyQueue->rear; i++) {
Process* process = readyQueue->processes[i];
if (process->runtime < shortestRuntime) {
shortestProcess = process;
shortestRuntime = process->runtime;
}
}
shortestProcess->state = 1; // 将进程状态设置为运行
enqueue(runningQueue, shortestProcess);
}
break;
case 3: // RR调度算法
if (!isEmpty(readyQueue)) {
Process* process = dequeue(readyQueue);
process->state = 1; // 将进程状态设置为运行
enqueue(runningQueue, process);
}
break;
default:
printf("无效的调度算法!\n");
break;
}
}
// 阻塞进程
void blockProcess(ProcessQueue* runningQueue, ProcessQueue* waitingQueue) {
if (!isEmpty(runningQueue)) {
Process* process = dequeue(runningQueue);
process->state = 2; // 将进程状态设置为阻塞
enqueue(waitingQueue, process);
}
}
// 唤醒进程
void wakeupProcess(ProcessQueue* waitingQueue, ProcessQueue* readyQueue) {
if (!isEmpty(waitingQueue)) {
Process* process = dequeue(waitingQueue);
process->state = 0; // 将进程状态设置为就绪
enqueue(readyQueue, process);
}
}
int main() {
int schedulingAlgorithm; // 调度算法标识,1表示FIFO,2表示SJF,3表示RR
ProcessQueue* readyQueue = initQueue(10); // 就绪队列
ProcessQueue* runningQueue = initQueue(1); // 运行队列,最多同时运行一个进程
ProcessQueue* waitingQueue = initQueue(10); // 等待队列
// 创建进程并加入就绪队列
Process* p1 = createProcess(1, 5);
Process* p2 = createProcess(2, 3);
Process* p3 = createProcess(3, 4);
enqueue(readyQueue, p1);
enqueue(readyQueue, p2);
enqueue(readyQueue, p3);
printf("请选择调度算法(1-FIFO,2-SJF,3-RR):");
scanf("%d", &schedulingAlgorithm);
// 进程调度
scheduleProcess(readyQueue, runningQueue, schedulingAlgorithm);
// 输出当前运行进程信息
if (!isEmpty(runningQueue)) {
Process* runningProcess = runningQueue->processes[runningQueue->front];
printf("当前运行进程:PID=%d,运行时间=%d\n", runningProcess->pid, runningProcess->runtime);
} else {
printf("当前无运行进程!\n");
}
// 阻塞进程
blockProcess(runningQueue, waitingQueue);
// 唤醒进程
wakeupProcess(waitingQueue, readyQueue);
free(readyQueue->processes);
free(readyQueue);
free(runningQueue->processes);
free(runningQueue);
free(waitingQueue->processes);
free(waitingQueue);
return 0;
}
```
请注意,这只是一个简单的示例代码,可能不包含所有边界情况和错误处理。实际上,模拟处理器管理功能的实现涉及更多的细节和复杂性,因此建议根据具体需求进行进一步的设计和开发。
用c语言 模拟 一个进程管理程序 拥有创建、撤销、阻塞、唤醒与调度等功能
这是一个简单的进程管理程序,可以创建、撤销、阻塞、唤醒和调度进程。
```
#include <stdio.h>
#include <stdlib.h>
#define MAX_PROCESS 10 // 最大进程数
typedef enum {READY, RUNNING, BLOCKED} state_t; // 进程状态
typedef struct {
int pid; // 进程ID
state_t state; // 进程状态
} process_t;
process_t processes[MAX_PROCESS]; // 进程数组
int num_processes = 0; // 进程数
// 创建进程
void create_process() {
if (num_processes == MAX_PROCESS) {
printf("Cannot create more processes!\n");
return;
}
process_t new_process;
new_process.pid = num_processes + 1;
new_process.state = READY;
processes[num_processes] = new_process;
num_processes++;
printf("Process %d created.\n", new_process.pid);
}
// 撤销进程
void destroy_process(int pid) {
int i;
for (i = 0; i < num_processes; i++) {
if (processes[i].pid == pid) {
// 撤销进程
printf("Process %d destroyed.\n", pid);
if (i != num_processes - 1) {
processes[i] = processes[num_processes - 1];
}
num_processes--;
return;
}
}
printf("Process %d not found!\n", pid);
}
// 阻塞进程
void block_process(int pid) {
int i;
for (i = 0; i < num_processes; i++) {
if (processes[i].pid == pid) {
// 阻塞进程
processes[i].state = BLOCKED;
printf("Process %d blocked.\n", pid);
return;
}
}
printf("Process %d not found!\n", pid);
}
// 唤醒进程
void unblock_process(int pid) {
int i;
for (i = 0; i < num_processes; i++) {
if (processes[i].pid == pid) {
// 唤醒进程
processes[i].state = READY;
printf("Process %d unblocked.\n", pid);
return;
}
}
printf("Process %d not found!\n", pid);
}
// 调度进程
void schedule() {
int i;
int running = -1;
// 找到正在运行的进程
for (i = 0; i < num_processes; i++) {
if (processes[i].state == RUNNING) {
running = i;
break;
}
}
// 如果没有正在运行的进程,就找到一个 READY 状态的进程运行
if (running == -1) {
for (i = 0; i < num_processes; i++) {
if (processes[i].state == READY) {
running = i;
processes[i].state = RUNNING;
printf("Process %d is running.\n", processes[i].pid);
break;
}
}
}
// 如果有正在运行的进程,就把它切换为 READY 状态,找到下一个 READY 状态的进程运行
if (running != -1) {
processes[running].state = READY;
for (i = (running + 1) % num_processes; i != running; i = (i + 1) % num_processes) {
if (processes[i].state == READY) {
processes[i].state = RUNNING;
printf("Process %d is running.\n", processes[i].pid);
break;
}
}
if (i == running) {
printf("No process is ready to run.\n");
}
}
}
int main() {
int choice, pid;
while (1) {
printf("1. Create process\n");
printf("2. Destroy process\n");
printf("3. Block process\n");
printf("4. Unblock process\n");
printf("5. Schedule process\n");
printf("6. Exit\n");
printf("Enter your choice: ");
scanf("%d", &choice);
switch (choice) {
case 1:
create_process();
break;
case 2:
printf("Enter process ID: ");
scanf("%d", &pid);
destroy_process(pid);
break;
case 3:
printf("Enter process ID: ");
scanf("%d", &pid);
block_process(pid);
break;
case 4:
printf("Enter process ID: ");
scanf("%d", &pid);
unblock_process(pid);
break;
case 5:
schedule();
break;
case 6:
exit(0);
default:
printf("Invalid choice!\n");
}
}
return 0;
}
```
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