string input with spaces

Question

I'm trying to run the following code in the basic ubuntu gcc compiler for a basic C class.

#include<stdio.h>

struct emp
{

  int emp_num, basic;
  char name[20], department[20];

};

struct emp read()
{
  struct emp dat;

  printf("\n Enter Name : \n");
  scanf("%s", dat.name);

  printf("Enter Employee no.");
  scanf("%d", &dat.emp_num);

  //printf("Enter department:");
  //fgets(dat->department,20,stdin);

  printf("Enter basic :");
  scanf("%d", &dat.basic);

  return dat;
}

void print(struct emp dat)
{
  printf("\n Name : %s", dat.name);

  printf("\nEmployee no. : %d", dat.emp_num);

  //printf("Department: %s", dat.department);

  printf("\nBasic : %d\n", dat.basic);
}

int main()
{
  struct emp list[10];

  for (int i = 0; i < 3; i++)
  {
    printf("Enter Employee data\n %d :\n", i + 1);
    list[i] = read();
  }

  printf("\n The data entered is as:\n");

  for (int i = 0; i < 3; i++)
  {
    print(list[i]);
  }

  return 0;
}

I want the name to accept spaces.

The problem comes when I'm entering the values to the structures. I am able to enter the name the first time but the subsequent iterations don't even prompt me for an input.

I've tried using fgets, scanf("%[^\n]",dat.name) and even gets() (I was desperate) but am the facing the same problem every time.

The output for the 1st struct is fine but for the rest is either garbage, the person's last name or just blank.

Any ideas?

Answer 1

When reading a string using scanf("%s"), you're reading up to the first white space character. This way, your strings cannot include spaces. You can use fgetsinstead, which reads up to the first newline character.

Also, for flushing the input buffer, you may want to use e.g. scanf("%d\n") instead of just scanf("%d"). Otherwise, a subsequent fgets will take the newline character and not ask you for input.

I suggest that you experiment with a tiny program that reads first one integer number and then a string. You'll see what I mean and it will be much easier to debug. If you have trouble with that, I suggest that you post a new question.

Answer 2

The problem is that scanf("%[^\n",.. and fgets don't skip over any whitespace that may be left over from the previous line read. In particular, they won't skip the newline at the end of the last line, so if that newline is still in the input buffer (which it will be when the last line was read with scanf("%d",..), the scanf will fail without reading anything (leaving random garbage in the name array), while the fgets will just read the newline.

The easiest fix is to add an explicit space in the scanf to skip whitespace:

printf("\n Enter Name : \n");
scanf(" %19[^\n]", dat.name);

This will also skip over any whitespace at the beginning of the line (and blank lines), so may be a problem if you want to have a name that begins with a space.

Note I also added a length limit of 19 to avoid overflowing the name array -- if the user enters a longer name, the rest of it will be left on the input and be read as the employeee number. You might want to skip over the rest of the line:

scanf("%*[^\n]");

This will read any non-newline characters left on the input and throw them away. You can combine this with the prior scanf, giving you code that looks like:

printf("\n Enter Name : ");
scanf(" %19[^\n]%*[^\n]", dat.name);
printf("Enter Employee no. : ");
scanf("%d%*[^\n]", &dat.emp_num);
printf("Enter department : ");
scanf(" %19[^\n]%*[^\n]", dat.department);
printf("Enter basic : ");
scanf("%d%*[^\n]", &dat.basic);

This will ignore any spurious extra stuff that someone enters on a line, but will still have problems with someone entering letters where numbers are expected, or end-of-file conditions. To deal with those, you need to be checking the return value of scanf.

Answer 3

What you have tried was:-

scanf("%[^\n]",dat.name)

In this you forgot to specify the specifier.

You can try to use this:-

scanf ("%[^\n]%*c", dat.name);

or fgets() if you want to read with spaces.

Note:- "%s" will read the input until whitespace is reached.