linux操作系统argv
时间: 2023-11-17 14:58:25 浏览: 124
在Linux操作系统中,argv是命令行参数表,它是一个指向字符串数组的指针,其中每个字符串都是一个命令行参数。当我们在终端输入一个命令时,这个命令会被解析成一个或多个参数,这些参数会被存储在argv数组中。例如,如果我们在终端输入命令"ls -l",那么argv数组中就会有两个元素,分别是"ls"和"-l"。这些参数可以被程序读取和使用,以便程序根据不同的参数执行不同的操作。
除了argv之外,Linux操作系统还有一个环境变量表env,它也是一个字符串数组,存储了一些环境变量的值。环境变量可以被程序读取和使用,以便程序根据不同的环境变量执行不同的操作。环境变量和命令行参数一样,都是通过父进程传递给子进程的。
总之,argv和env都是Linux操作系统中非常重要的概念,它们可以帮助程序读取和使用命令行参数和环境变量,从而实现不同的功能。
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linux操作系统银行家代码
银行家算法是一种用于避免死锁的算法,它用来确保在分配资源时不会进入不安全的状态。以下是一个在Linux操作系统下实现银行家算法的示例代码:
```c
#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#define MAX_PROCESSES 10
#define MAX_RESOURCES 10
int available[MAX_RESOURCES];
int allocation[MAX_PROCESSES][MAX_RESOURCES];
int max[MAX_PROCESSES][MAX_RESOURCES];
int need[MAX_PROCESSES][MAX_RESOURCES];
bool finished[MAX_PROCESSES] = {false};
int num_processes;
int num_resources;
bool is_safe() {
int work[MAX_RESOURCES];
for (int i = 0; i < num_resources; i++) {
work[i] = available[i];
}
bool can_finish = true;
int safe_sequence[MAX_PROCESSES];
int num_finished = 0;
while (num_finished < num_processes && can_finish) {
can_finish = false;
for (int i = 0; i < num_processes; i++) {
if (!finished[i]) {
bool can_allocate = true;
for (int j = 0; j < num_resources; j++) {
if (need[i][j] > work[j]) {
can_allocate = false;
break;
}
}
if (can_allocate) {
for (int j = 0; j < num_resources; j++) {
work[j] += allocation[i][j];
}
safe_sequence[num_finished] = i;
num_finished++;
finished[i] = true;
can_finish = true;
}
}
}
}
if (num_finished == num_processes) {
printf("Safe sequence: ");
for (int i = 0; i < num_processes; i++) {
printf("%d ", safe_sequence[i]);
}
printf("\n");
return true;
} else {
printf("Not safe!\n");
return false;
}
}
int request_resources(int pid, int *request) {
for (int i = 0; i < num_resources; i++) {
if (request[i] > need[pid][i] || request[i] > available[i]) {
return -1;
}
}
for (int i = 0; i < num_resources; i++) {
available[i] -= request[i];
allocation[pid][i] += request[i];
need[pid][i] -= request[i];
}
if (is_safe()) {
return 0;
} else {
for (int i = 0; i < num_resources; i++) {
available[i] += request[i];
allocation[pid][i] -= request[i];
need[pid][i] += request[i];
}
return -1;
}
}
int release_resources(int pid, int *release) {
for (int i = 0; i < num_resources; i++) {
if (release[i] > allocation[pid][i]) {
return -1;
}
}
for (int i = 0; i < num_resources; i++) {
available[i] += release[i];
allocation[pid][i] -= release[i];
need[pid][i] += release[i];
}
return 0;
}
int main(int argc, char **argv) {
if (argc <= 1) {
printf("Usage: ./banker <num_processes> <num_resources> <resource1> ... <resourceN>\n");
return -1;
}
num_processes = atoi(argv[1]);
num_resources = atoi(argv[2]);
if (num_processes > MAX_PROCESSES || num_resources > MAX_RESOURCES) {
printf("Too many processes or resources!\n");
return -1;
}
for (int i = 0; i < num_resources; i++) {
available[i] = atoi(argv[3 + i]);
}
for (int i = 0; i < num_processes; i++) {
for (int j = 0; j < num_resources; j++) {
allocation[i][j] = 0;
need[i][j] = 0;
finished[i] = false;
}
}
while (true) {
char command;
int pid;
int request[MAX_RESOURCES];
int release[MAX_RESOURCES];
printf("> ");
if (scanf("%c", &command) == EOF) {
break;
}
switch (command) {
case 'i':
scanf("%d", &pid);
for (int i = 0; i < num_resources; i++) {
scanf("%d", &max[pid][i]);
need[pid][i] = max[pid][i] - allocation[pid][i];
}
break;
case 'q':
scanf("%d", &pid);
for (int i = 0; i < num_resources; i++) {
printf("%d ", need[pid][i]);
}
printf("\n");
break;
case 'r':
scanf("%d", &pid);
for (int i = 0; i < num_resources; i++) {
scanf("%d", &request[i]);
}
if (request_resources(pid, request) == -1) {
printf("Request denied\n");
}
break;
case 'f':
scanf("%d", &pid);
for (int i = 0; i < num_resources; i++) {
scanf("%d", &release[i]);
}
release_resources(pid, release);
break;
case 's':
is_safe();
break;
default:
break;
}
while (getchar() != '\n');
}
return 0;
}
```
该代码使用命令行界面与用户进行交互,支持以下命令:
- `i <pid> <r1> <r2> ... <rn>`:为进程 `<pid>` 指定最大的资源需求量。
- `q <pid>`:查询进程 `<pid>` 的当前资源需求量。
- `r <pid> <r1> <r2> ... <rn>`:请求进程 `<pid>` 的资源。
- `f <pid> <r1> <r2> ... <rn>`:释放进程 `<pid>` 的资源。
- `s`:检查系统是否处于安全状态。
可以根据需要进行修改和扩展。
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