Why I can not use the inputted value from one-dimensional array, in C?

Question

I understand that: I can use a two-dimensional array for storaging many strings. But, I would like to solve this problem with one-dimensional; so, please do not advise me to use two-dimensional array for solving.

I have a small one-dimensional array, which is used for storaging many strings. Here is all of source code:

#include <stdio.h>

void main()
{
    #define MAX 10

    int N = 3;

    char * str[MAX];

    printf("Input a string in each line:\n\n");

    for (int i = 0; i < N; i++)
    {
        printf("str[%d] = ", i);
         gets(str[i]);
    }

    printf("\n\n---\n\nExport the list of strings:\n\n");

    for (int j = 0; j < N; j++)
    {
        printf("str[%d] = ", j);
        printf("%s\n", str[j]);
    }

}

When I compile it, the compiler does not return any error or warning. But, after I inputted the data, there is an error message from Windows:

A problem caused the program to stop working correctly

Then, my program is broken.

`&str[i]` is incorrect and you don't allocate any memory for the strings either. — Lundin, Dec 14 '16 at 08:26
Related: [Reading a string with scanf](http://stackoverflow.com/questions/5406935/reading-a-string-with-scanf) — qxz, Dec 14 '16 at 08:27
`char str[MAX];` is 1D-Array. Why do you think it is different? — BLUEPIXY, Dec 14 '16 at 08:38
Have you ever heard about Array of Pointers, or moreover about Pointers? — Michi, Dec 14 '16 at 09:10

score 3 · Answer 1 · answered Dec 14 '16 at 08:24

3

In this array: char * str[MAX]

None of the entries is initialized to point to a valid (properly allocated) memory block.

And so you should not scanf("%s", &str[i]) until you have initialized entry #i.

answered Dec 14 '16 at 08:24

barak manos

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score 1 · Answer 2 · answered Dec 14 '16 at 08:26

1

char * str[MAX];

str is an array of pointers. You should allocate memory to pointers before writing anything to it.

str[i] = malloc(20);/* Showing an example of using malloc() . How much memory should be allocated is left to you */

Using a scanf() to scan a string is not a good idea I would rather prefer fgets()

answered Dec 14 '16 at 08:26

Gopi

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What's wrong with scanf? It is almost always wrong used. – Michi Dec 14 '16 at 09:21

Why I can not use the inputted value from one-dimensional array, in C?

2 Answers2