如何使用 fgets() 和 sscanf

Question

Suppose there is a case: input required:

Name of Player
Height of Player
Age of Player

User may input in such a way that he may press enter(\n) after each input.

printf("Please enter Name, Height and Age of Player");

All I want to take this input with the combination of fgets() and sscanf()

Answer 1

You can define a function that does that for you:

bool readline(char *line, size_t size, FILE *stream)
{
    if (!fgets(line, size, stream))
        return false;
    
    size_t npos = strcspn(line, "\n");
    if (line[npos] != '\n') {
        flush_stdin();
        return false;
    }

    line[npos] = '\0';
    return true;
}

• line : the char buffer that will hold your input.
• size : the size (capacity) of line .
• stream : the file stream you want to read from.

In case the number of characters read exceeds the capacity of the buffer, one must flush the input buffer:

int flush_stdin(void)
{
    int c = 0;
    while ((c = getchar()) != EOF && c != '\n');
    return c;
}

As for sscanf() , use it to parse what has been read by fgets() .

Here is a demo:

int main(void)
{
    char input[64], name[64];
    printf("Enter your name: ");
    readline(name, sizeof(name), stdin);
    
    printf("Enter your height: ");
    readline(input, sizeof(input), stdin);
    
    float height = .0;
    if (sscanf(input, "%f", &height) != 1) {
        printf("Input error\n");
        return 1;
    }
    
    printf("Enter your age: ");
    readline(input, sizeof(input), stdin);
    
    int age = 0;
    if (sscanf(input, "%d", &age) != 1) {
        printf("Input error\n");
        return 1;
    }
    
    printf("%s is %d years old and %.2f feet tall.\n", name, age, height);
}

Enter your name: Johnny
Enter your height: 5.6
Enter your age: 18
Johnny is 18 years old and 5.60 feet tall.

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Notes:

• Never use fflush(stdin) .
• Skipped checking for readline() return values for simplicity.