在 C 中计算行数并显示结构数组

Question

这就是我到目前为止所拥有的。我需要读取文件day.txt，计算文件中的行数

#include "stdio.h"
#include "stdlib.h" 

#define MAX_LINE_LENGTH 

struct earthquake_t{ 
    float lat;
float lng;
float dep;
float mag;
};
FILE* fid;
int main(void)
{
double lat,lng dep,mag;
double userminlat,userminlng,usermaxlat,usermaxlng,minlat,minlng,maxlat,maxlng,i, ch,line;
struct earthquake_t *earthquake;

fid=fopen("day.txt","r");

while (!feof(fid))
{        /*Need help counting lines*/
    count = fscanf(fid," %lf %lf %lf\n",&lng,&lat,&dep,&mag);
/* count tell you how many of the % fields were matched,
 and you need to make sure all three were found to avoid blank lines*/

    if (count ==3)
    {
        line ++;
    }
}

fseek(fid,1,SEEK_SET);
print("%d\n",sizeof(struct earthquake_t));        
earthquake = (struct earthquake_t *)malloc(sizeof(struct earthquake_t)*line);

for (i=0;i<line;i++)
{        
    fscanf("fid,%lf %lf %lf\n",&lng,&lati,&elevi)
    earthquake[i].lat=lat;
    earthquake[i].lng=lng;
    earthquake[i].dep=dep;
    earthquake[i].mag=mag;


    /*Setting the min and max values for latitude and longatidue*/
    if(earthquake[i].lng >maxlng) 
    {     
        maxlng = earthquake[i].lng;
    }
    if(earthquake[i].lng >minlng)
    {    
        minlng = earthquake[i].lng;
    }
    if(earthquake[i].lat >maxlat)
    {
        maxlat = earthquake[i].lat;
    }
    if(earthquake[i].lat >minlat)
    {
        minlat = earthquake[i].lat;
    }

}

Answer 1

我将使用 fgets() 从文本文件中获取整行并将其放入字符串中，然后使用 sscanf() 提取您的值。

/* count tell you how many of the % fields were matched,
and you need to make sure all three were found to avoid blank lines*/

scanf man page部分说明:

返回值

这些函数返回成功匹配和分配的输入项的数量，该数量可能少于提供的数量，如果早期匹配失败，甚至为零。

如果在第一次成功转换或匹配失败发生之前到达输入末尾，则返回值 EOF。如果发生读取错误，也会返回 EOF，在这种情况下，会设置流的错误指示符(请参阅ferror(3))，并设置 errno 来指示错误。

您可以检查 line[0] == '\n' 以避免空行。

希望有帮助。