fscanf读取两次行

Question

I'm using fscanf in a text file like this:

T 1 1000
T 2 700
N 3 450
Y 4 200

I'm trying to count the lines to use a malloc and to do that I use:

Prize temp;
int count =0;
while ((fscanf(fa,"%c %d %f", &temp.A, &temp.B, &temp.C))!= EOF)
count ++;

where Prize is a struct:

typedef struct {
  char A;
  int B;
  float C;
} Prize;

So, after reading the lines the program prints me this:

 A: T B: 1 C: 1000.0000
 A:   B: 0 C: 0.0000
 A: T B: 2 C: 700.0000
 A:   B: 0 C: 0.0000
 A: N B: 3 C: 450.0000
 A:   B: 0 C: 0.0000
 A: Y B: 4 C: 200.0000

Using the debugger I noticed that fscanf gets (for example while reading the first line):

A = 84 'T', B=1, C=1000

and instead of reading the second line it reads another first line, but like this:

A = 10'\\n', B=1, C=1000

and continues doing this for each line but the last.

I controlled the file and it doesn't have extra spaces or lines.

Any suggestions to solve the problem?

Answer 1

Your file contains newlines. So the sequence of characters in the file is really as following:

T 1 1000\nT 2 700\n...

The first fscanf reads 'T' , 1 , and 1000 . It stops at the '\\n' character.

The seconds fscanf reads the '\\n' character to temp.A . Now it is at the second 'T' character. Therefore, it is unable to read temp.B and temp.C

The third fscanf reads 'T' , 2 , and 700 , but stops at '\\n' again.

You should skip all whitespace characters before reading temp.A , which is done by the space in the format string:

...fscanf(fa," %c %d %f", &temp.A, &temp.B, &temp.C)...

Answer 2

The %c format of the reading would not ignore any space or \\n character, even which it is unseen. However %s %d %c will. It is likely the better way to avoid the inconsistency if replace %c by %s (and single character to be a string).

char str[maxn];
fscanf(fa, "%s%d%f", str, &temp.B, &temp.C);
temp.A = str[0];