LinuxProc文件系统实验（代码）

Linux上的/proc目录是一种文件系统，称为proc文件系统（虚拟文件系统），它存储内核状态信息，包括cpu、内存以及进程等信息。proc文件系统有很多优点：应用程序获取内核数据不用切换到内核态，增加了系统的安全性（像ps命令就是通过proc获取进程信息）；应用程序可以通过proc直接改变内核参数，这样不用重新编译内核就可以改变和优化内核行为。总之，proc为用户应用程序获取系统内部信息提供了一个安全、方便的界面。proc存在内存中，不占用外存。

下面是/proc目录下的文件： 

下面是我自己写得一个查看cpu和内核版本信息以及启动时间的程序：

因为要涉及文件读写，先介绍一下几个文件读写函数。

1)fgetc从流中读取一个字符，并增加文件指针的位置，常与EOF配合使用，将流中的字符全部读出。

2)putchar向终端输出一个字符。

3)fgets(char *s, int size, FILE *stream)，从文件流中读取一行到s中，size一般为数组s的大小，且s以字符'/0'结束。

4)int feof(FILE *stream)判断是否遇到文件结束，如果遇到则返回非零值，否则为0。

5)int fscanf(FILE *stream, const char *format, ...)从文件流（或标准输入）中进行格式化输入，用法如下：

#include<stdio.h>int main(){       int i;    char s[5];    fscanf(stdin, "%d %5[a-z]%*s", &i, s);    printf("%d %s /n", i, s);    return 0;    }

#include<stdio.h>#include<sys/time.h>#define LB_SIZE 80enum TYPE{STANDARD, SHORT, LONG};FILE *thisProcFile; //Proc open file pointerstruct timeval now; //system time dateenum TYPE reportType; //the type of observation reportchar repTypeName[16];char *lineBuf; //read out bufferint interval; //system overload detect intervalint duration; //system overload detect durationint iteration;char c1, c2; //character handle uintvoid getTwoTime(FILE *fp) {	long uptime, idletime;	int day, hour,minute, second;	int m, n;	char temp[80];	m = n = 0;	int ret;	int i = 0;	char s[100][100];	int j;	while((ret=fscanf(fp, "%s", s[i])) != EOF) i++;		//print	for(j = 0; j < i; j++)	{		printf("%s/n", s[j]);	}	uptime = atol(s[0]);	idletime = atol(s[1]);	printf("<<---------------------___________------------------------->/n");	printf("the uptime of system -----------------------------> %ld/n", uptime);	printf("the idletime of process -----------------------------> %ld/n", idletime);	printf("<<---------------------___________------------------------->/n");	/*	time_t uptime_timet = uptime;	printf("xixixixixi%ld/n", uptime_timet);	char *result = ctime(&uptime_timet); 		printf("hahahahahahah %s/n", result);*/	int days;	int hours;	int minutes;	int seconds;	//uptime of system	days = (int)uptime/86400;	hours = (int)uptime%86400/3600;	minutes = (int)uptime%3600/60;	seconds = (int)uptime%3600%60;	printf("the uptime of system-------------days %d----hours %d-----minutes %d-----seconds %d----/n", days, hours, minutes, seconds);		//idletime	days = (int)idletime/86400;	hours = (int)idletime%86400/3600;	minutes = (int)idletime%3600/60;	seconds = (int)idletime%3600%60;	printf("the idletime of system-------------days %d----hours %d-----minutes %d-----seconds %d----/n", days, hours, minutes, seconds);}//get time from startingvoid sampleTime(){	//open timer file	FILE *fp;	if((fp=fopen("/proc/uptime", "r")) == NULL)	{		printf("not open /proc/uptime");		exit(0);	}		getTwoTime(fp);		fclose(fp);}void getCPUinfo(){	FILE *cpuinfo;	char ch;	if((cpuinfo=fopen("/proc/cpuinfo","r")) == NULL)	{		printf("not open /proc/cpuinfo");		exit(0);	}	/*	while((ch=fgetc(cpuinfo)) != EOF)		putchar(ch);	fclose(cpuinfo);*/	printf("*********************cpu*******************/n");		while(!feof(cpuinfo))	{		fgets(lineBuf, LB_SIZE+1, cpuinfo);		printf("%s", lineBuf);	}		fclose(cpuinfo);}void getKernelVersion() {		FILE *version;	char ch;	if((version=fopen("/proc/version","r")) == NULL)	{		printf("not open /proc/version");		exit(0);	}	printf("*****************version*************************/n");	while(!feof(version))	{		fgets(lineBuf, LB_SIZE+1, version);		printf("%s", lineBuf);	}		fclose(version);}int main(int argc, char *argv[]) {	lineBuf = (char *)malloc(LB_SIZE + 1);	reportType = STANDARD;	strcpy(repTypeName, "Standard");	if(argc > 1) 	{		sscanf(argv[1], "%c%c", &c1, &c2);		if(c1 != '-')  exit(1);		if(c2 == 'b')		{			printf("********************************Memory Info*********************************/n");			//open memory info 			FILE *meminfo; 			char ch;			if((meminfo=fopen("/proc/meminfo","r")) == NULL)			{				printf("not open /proc/meminfo");				exit(0);			}			while((ch=fgetc(meminfo)) != EOF)				putchar(ch);			fclose(meminfo);						printf("********************************TIME*********************************/n");			//cat the start time			sampleTime();		} else if(c2 == 'c')		{			//get cpu info and kernel version			printf("*************************CPU & kernel*************************/n");						getCPUinfo();			getKernelVersion();					}	}}

./main -b 查看内存信息以及经过格式化的启动时间。

./main -c查看cpu类型和kernel版本。