我如何获取fscanf来读取.csv文件，将逗号之间以及每一行中的每一节读入字符串？

Question

I'm writing a program to read a map from a .csv file, and I want to read each section of the file and then write the information from it into a relevant struct in a 2D array. I use fscanf to get the number of rows and columns to malloc the array of structs, and I can read the first value up until the comma and deal with it. However, there can also be blank fields, that appear in a line such as 1 goat,,2 cat My program reads the 1 and goat and deals with that, but then the next thing it scans is just cat. I want it to read the 2 commas, recognize there's nothing in them, and then move on to the cat and read that before moving on to the next line

I don't know how to do the correct format specifications for the fscanf. Currently I've got fscanf(fp, "%[^,]", animal);

/*scans file until comma, writes the scanned text into array*/

              fscanf(fp, "%[^,]", animal);
              printf("Scanned in string for y (%d) and x %d = (%s)\n", j, k, anima;l);
              if (strcmp(animal, "") != 0)
              {   
                  /*if first character is lowercase, change to upper)*/
                  if(animal[0]>90)
                  {
                      animal[0]=animal[0]-32;
                  }
                  /*Checks if item is cat goat or mouse by checking 1st letter of the scanned in array is C G or M*/                     
                  if(strncmp(animal,"C", 1) == 0)             
                  {
                      /*copies name of the animal into the struct*/
                      strcpy(animalarray[j][k].name, "Cat");

                      /*write animal name into struct*/
                      token =strtok(animal, spaceDelimeter);
                      /* The 1 is already dealt with, can be moved past*/
                      token = strtok(NULL, commaDelimeter);
                      printf("token = %s\n", token);


                      animalarray[j][k].number= atoi(token); 


                      printf("Animal is %s, number is %d\n", animalarray[j][k].name, animalarray[j][k].number);
                  }  

The Input File is ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

2,3 1 goat,,2 cat 3 mouse, 5 goat,

The output when i run is

rows  2, columns  3 
Scanned in string for row 0 and column 0 = 1 goat
token = goat
Animal is goat, number is 1
Scanned in string for row 0 and column 1 = 2
token = (null)
Segmentation fault (core dumped)

it should be

...
Scanned in string for row 0 and column 1 = "blank"
Scanned in string for row 0 and column 1 = 2 cat
...

Answer 1

fscanf cannot scan empty strings, but you can use the return value to detect whether there was anything scanned at all:

FILE *f = fopen(filename, "r");
char buf[80];
int row = 0;
int col = 0;

while (1) {
    int n = fscanf(f, "%79[^,\n]", buf);

    if (n == EOF) break;
    if (n == 0) *buf = '\0';

    printf("[%d, %d] '%s'\n", row, col, buf);

    if (fgetc(f) == ',') {
        col++;
    } else {
        col = 0;
        row++;
    }
}

If nothing was acanned, n is 0- In that case, the code explicitly clears the input string by writing the null terminator in the first char. Rows and columns are detected by whether an comma or a newline was read. (The next character can only be a comma, a newline or the end of the file.)

Another possibility is to read the input line-wise with fgets and then scan each line. The string scanning function sscanf has the same limitations as fscanf , so it might be better to use string functions, such as strchr . Here I have used strcspn from <string.h> , which counts the characters in a string until any of the given characters or the end of the string are found. That makes it very similar to the %[^n ...] format in fscanf :

FILE *f = fopen(filename, "r");
char line[80];
int row = 0;

while (fgets(line, sizeof(line), f)) {
    int col = 0;
    int offset = 0;

    while (line[offset]) {
        int next = strcspn(line + offset, ",\n");

        printf("[%d, %d] '%.*s'\n", row, col, next, line + offset);
        offset += next + 1;

        col++;
    }

    row++;
}

Again, column and line detection are by context.