读取 3 个文件并从中制作 arrays

Question

I have three text files which contains a list of lines and each line is comprised a latitude longitude, and value. These arrays cover different ranges of latitude and longitude. Now what I want to make three different latitude arrays, three different longitude arrays, and three different value arrays where each text file is supposed to generate one latitude,longitude and value array each.

Below I have the code in c in which I am attempting to accomplish this:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>


int main(int argc, char *argv[])
{
    FILE    *fp=NULL, *fpb=NULL, *fpc=NULL, *FPOUT=NULL;
    char    inpFname[81],inpFnameb[81],inpFnamec[81],FILEOUT[81];
    int     i,j,k;
    char    buf[8000];
    int     count;
    char    datetime[10],year[4],month[2],day[2],hour[2],type[10];

    float   latnum,lonnum,valnum;
    float   latnumb,lonnumb,valnumb;
    float   latnumc,lonnumc,valnumc;

    float*  latarray = malloc(sizeof(float) * 1038240);
    float*  lonarray = malloc(sizeof(float) * 1038240);
    float*  valarray = malloc(sizeof(float) * 1038240);

    float*  latarrayb = malloc(sizeof(float) * 3185);
    float*  lonarrayb = malloc(sizeof(float) * 3185);
    float*  valarrayb = malloc(sizeof(float) * 3185);

    float*  latarrayc = malloc(sizeof(float) * 5265);
    float*  lonarrayc = malloc(sizeof(float) * 5265);
    float*  valarrayc = malloc(sizeof(float) * 5265);


    sprintf(datetime,"%s",argv[1]);


    sprintf(inpFname,"100_%s.txt1",datetime);
    printf("%s\n",inpFname);

    if ((fp=fopen(inpFname,"rt"))==NULL)
    {
        printf("\nERROR: Cannot open/read input file [%s]\n\n",inpFname);
        exit(1);
    } 

    i=0;
    while(i < 1038240 && fgets(buf,sizeof buf, fp))
    {
        sscanf(buf,"%f %f %f\n",&latnum,&lonnum,&valnum);
    
        latarray[i]=latnum;
        lonarray[i]=lonnum;
        valarray[i]=valnum;
    
    
        i=i+1;  
    }
    fclose(fp);

    sprintf(inpFnameb,"100_%s.txt2",datetime);
    printf("%s\n",inpFnameb);

    if ((fpb=fopen(inpFnameb,"rt"))==NULL)
    {
        printf("\nERROR: Cannot open/read input file [%s]\n\n",inpFnameb);
    }

    i=0;
    while(i < 3185 && fgets(buf,sizeof buf, fpb))
    {
        sscanf(buf,"%f %f %f\n",&latnumb,&lonnumb,&valnumb);
    
        latarrayb[i]=latnumb;
        lonarrayb[i]=lonnumb;
        valarrayb[i]=valnumb;
    
        i=i+1;  
    }
    fclose(fpb);

    sprintf(inpFnamec,"100_%s.txt3",datetime);
    printf("%s\n",inpFnamec);

    if ((fpc=fopen(inpFnamec,"rt"))==NULL)
    {
        printf("\nERROR: Cannot open/read input file [%s]\n\n",inpFnamec);
    }

    i=0;
    while(i < 3185 && fgets(buf,sizeof buf, fpb))
    {
        sscanf(buf,"%f %f %f\n",&latnumc,&lonnumc,&valnumc);
    
        latarrayc[i]=latnumc;
        lonarrayc[i]=lonnumc;
        valarrayc[i]=valnumc;
    
        i=i+1;  
    }
    fclose(fpc);


}

Unfortunately when running this code I am getting a segmenation fault. It I take the third set of arrays out (arrayc), I do not get this segmentation fault so there must be a memory issue possibly. How do I tweak this program so as not to get a segmentation fault and be able to achieve my desired result of getting a latitude, longitude and value array for each file for a total of 9 arrays?

Answer 1

Instead of creating 3 sets of arrays and combining them later, you can create one set of arrays large enough for all the files, read the data directly in to the large array.

All the files appear to have the same format, so use a function to repeat the same read operation. There is no need for 3 sets of temporary variables for each file.

Open the files with "r" format. Valid open read modes are "r" or "rb" for binary.

Add error checks for malloc , sscanf , argc . Remove variables which are not used.

You can improve the code by using realloc , this way you don't have to know the size of the array ahead of time.

void readfile(const char *filename, int *iptr, int count,
    float* latarray, float* lonarray, float* valarray)
{
    int i = *iptr;
    char buf[8000];
    FILE* fp = fopen(filename, "r");
    if (!fp) { perror(filename); exit(1); }
    while (i < count && fgets(buf, sizeof buf, fp))
    {
        if (sscanf(buf, "%f %f %f\n", 
            &latarray[i], &lonarray[i], &valarray[i]) != 3)
            continue;
        i++;
    }
    *iptr = i;
    fclose(fp);
}

int main(int argc, char* argv[])
{
    if (argc < 2) return 0;
    char datetime[10];
    sprintf(datetime, "%s", argv[1]);

    char filename[100];

    int i = 0;
    int count = 1038240 + 3185 + 5265;
    float* latarray = malloc(sizeof(float) * count);
    float* lonarray = malloc(sizeof(float) * count);
    float* valarray = malloc(sizeof(float) * count);
    if (!latarray) return 0;
    if (!lonarray) return 0;
    if (!valarray) return 0;    

    sprintf(filename, "100_%s.txt1", datetime);
    readfile(filename, &i, count, latarray, lonarray, valarray);

    sprintf(filename, "100_%s.txt2", datetime);
    readfile(filename, &i, count, latarray, lonarray, valarray);

    sprintf(filename, "100_%s.txt3", datetime);
    readfile(filename, &i, count, latarray, lonarray, valarray);

    printf("Total lines read: %d\n", i);

    free(latarray);
    free(lonarray);
    free(valarray);

    return 0;
}