How do you allow spaces to be entered using scanf?

Question

Using the following code:

char *name = malloc(sizeof(char) + 256); 

printf("What is your name? ");
scanf("%s", name);

printf("Hello %s. Nice to meet you.\n", name);

A user can enter their name but when they enter a name with a space like Lucas Aardvark, scanf() just cuts off everything after Lucas. How do I make scanf() allow spaces

Answer 1

Try scanf("%10[0-9a-zA-Z ]s", str);

Hope that helps.

Edited because I forgot what language we are using.

Answer 2

People (and especially beginners) should never use scanf() or gets() or any of those functions that do not have buffer overflow protection.

Just remember than scanf stands for "scan formatted" and there's precious little less formatted than user-entered data. It's ideal if you have total control of the input data format but generally unsuitable for user input.

Use fgets() to get your input into a string and sscanf() to evaluate it. Since you just want what the user entered, you don't really need sscanf() in this case anyway:

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

/* Maximum name size + 1. */
#define MAX_NAME_SZ 256

int main(int argC, char *argV[]) {
    /* Allocate memory and check if okay. */
    char *name = malloc (MAX_NAME_SZ);
    if (name == NULL) {
        printf ("No memory\n");
        return 1;
    }

    /* Ask user for name. */
    printf("What is your name? ");

    /* Get the name, with size limit. */
    fgets (name, MAX_NAME_SZ, stdin);

    /* Remove trailing newline, if there. */
    if (name[strlen (name) - 1] == '\n')
        name[strlen (name) - 1] = '\0';

    /* Say hello. */
    printf("Hello %s. Nice to meet you.\n", name);

    /* Free memory and exit. */
    free (name);
    return 0;
}

Answer 3

Don't use scanf() to read strings without specifying a field width. You should also check the return values for errors:

#include <stdio.h>

#define NAME_MAX    80
#define NAME_MAX_S "80"

int main(void)
{
    static char name[NAME_MAX + 1]; // + 1 because of null
    if(scanf("%" NAME_MAX_S "[^\n]", name) != 1)
    {
        fputs("io error or premature end of line\n", stderr);
        return 1;
    }

    printf("Hello %s. Nice to meet you.\n", name);
}

Alternatively, use fgets():

#include <stdio.h>

#define NAME_MAX 80

int main(void)
{
    static char name[NAME_MAX + 2]; // + 2 because of newline and null
    if(!fgets(name, sizeof(name), stdin))
    {
        fputs("io error\n", stderr);
        return 1;
    }

    // don't print newline
    printf("Hello %.*s. Nice to meet you.\n", strlen(name) - 1, name);
}

Answer 4

getline()

Now in the standard library, none-the-less.

It also takes care of the buffer allocation problem that you asked about earlier, though you have to take care of freeing the memory.

Answer 5

This example uses an inverted scanset, so scanf keeps taking in values until it encounters a '\n'-- newline, so spaces get saved as well

#include <stdio.h>

int main (int argc, char const *argv[])
{
    char name[20];
    scanf("%[^\n]s",name);
    printf("%s\n", name);
    return 0;
}

Answer 6

Refer Accepting Paragraph using Scanf : Click Here