C语言文件操作与时间测量-优快云博客

本文链接：https://blog.youkuaiyun.com/lin_FS/article/details/7160285

本文通过两个示例介绍了如何使用C语言进行文件读取操作，并分别采用秒级别和毫秒级别的时间测量来评估文件打开及读取的耗时。示例中详细展示了结构体的定义与使用、内存分配、文件指针操作等关键技术点。

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秒级别的：

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
int main()
{
time_t cur;

time(&cur);
printf("opencur1=%d\n",cur);

FILE *file=fopen("a.txt","r");
if(file==NULL){printf("file open failed!\n");}

time(&cur);
printf("opencur2=%d\n",cur);

typedef struct{
  int id;
  char name[10];
  double sal;
  }Emp;

Emp*es2=malloc(sizeof(Emp));

time(&cur);
printf("readcur1=%d\n",cur);

int n=fread(es2,sizeof(Emp),1,file);

time(&cur);
printf("readcur2=%d\n",cur);
fclose(file);

for(int i=0;i<n;i++){
  printf("%d,%s,%g\n",es2[i].id,es2[i].name,es2[i].sal);
}
free(es2);

}

毫秒级别的：

#include<stdio.h>
#include<sys/time.h>
#include<stdlib.h>
int main()
{
struct timeval t_start,t_end;
long const_timeopen=0;
long const_timeread=0;

//get opent sart time
gettimeofday(&t_start,NULL);
printf("start open time :%ld us\n",t_start.tv_usec);

FILE *file=fopen("test.info.swp","r");
if(file==NULL){printf("file open failed!\n");}

//get end time
gettimeofday(&t_end,NULL);
printf("end open time:%ld us\n",t_end.tv_usec);

//const open time
const_timeopen=t_end.tv_usec-t_start.tv_usec;
printf("const open time :%ld us\n",const_timeopen);

typedef struct{
  int id;
  char name[10];
  double sal;
  }Emp;

Emp*es2=malloc(sizeof(Emp));

//get read sart time
gettimeofday(&t_start,NULL);
printf("start read time :%ld us\n",t_start.tv_usec);

int n=fread(es2,sizeof(Emp),1,file);

//get end time
gettimeofday(&t_end,NULL);
printf("end read time:%ld us\n",t_end.tv_usec);

//const read time
const_timeread=t_end.tv_usec-t_start.tv_usec;
printf("const read time :%ld us\n",const_timeread);

fclose(file);

for(int i=0;i<n;i++){
  printf("%d,%s,%g\n",es2[i].id,es2[i].name,es2[i].sal);
}
free(es2);

}