Code -

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

int main()
{
    char *e;
    int len;

    for (int i = 1; i < 4; i  )
    {
        printf("Enter the size of the ID of the Employee %d\n", i);
        scanf("%d", &len);

        printf("Enter Employee ID of Employee %d\n", i);
        scanf("%s", &e);
    }

    e = (char *)malloc((len   1) * sizeof(char));

    for (int i = 1; i < 4; i  )
    {
        printf("ID of Employee %d is %s\n", i, e);
    }

    return 0;
}

Terminal -

Enter the size of the ID of the Employee 1
2
Enter Employee ID of Employee 1
A2
Enter the size of the ID of the Employee 2
2
Enter Employee ID of Employee 2
A7
Enter the size of the ID of the Employee 3
3
Enter Employee ID of Employee 3
AA1

Expected Output -

ID of Employee 1 is A2
ID of Employee 2 is A7
ID of Employee 3 is AA1

Output I am getting -

»D of Employee 1 is Φ
»D of Employee 2 is Φ
»D of Employee 3 is Φ

Here, »D and Φ refers to Garbage Value that changes every time when I run it in another terminal

I'm just learning the basics of Dynamic Memory Allocation but getting problems even in that
Pls Help

CodePudding user response：

In addition to the comments above, you have a glaring mistake in that you are attempting to use the memory before you've allocated it. Try this:

#include <string.h>

#define MAX_EMP 3

int main()
{
    char *e[MAX_EMP];
    int len[3];

    for (int i = 0; i < MAX_EMP; i  )
    {
        printf("Enter the size of the ID of the Employee %d\n", i   1);
        scanf(" %d ", &len[i]);

        e[i] = (char*)malloc((len   1) * sizeof(char));
        printf("Enter Employee ID of Employee %d\n", i   1);
        scanf(" %s ", e[i]);
    }

    for (int i = 0; i < MAX_EMP; i  )
        printf("ID of Employee %d is %s\n", i   1, e[i]);

    return 0;
}

Also, note that memory resources are rarely at such a premium that dynamic memory allocation makes sense for such small strings. It's more practical to just do this:

#include <string.h>

#define MAX_EMP 3
#define MAX_LEN 10

int main()
{
    char e[MAX_EMP][MAX_LEN   1];

    for (int i = 0; i < MAX_EMP; i  )
    {
        printf("Enter Employee ID of Employee #%d\n", i   1);
        fgets(e[i],MAX_LEN   1,stdin);
    }

    for (int i = 0; i < MAX_EMP; i  )
        printf("ID of Employee #%d is %s\n", i   1, e[i]);

    return 0;
}

CodePudding user response：

• you need to store the data for every employee (probably in an array)
• in scanf("%s", something) something must be of type char *. In your code it is char **.
• don't use scanf %s because it assumes the buffer is large enough for the input. Use fgets or scanf %ms
• in new versions there is also scanf("%ms", something) where something is char **. It allocates the string and stores the pointer to it in *something
• having i start at 0 is easier when working with arrays

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

int main()
{
    char *ids[3];   // store the id for every employee, no need to store the length

    for (int i = 0; i < 3; i  )
    {
        printf("Enter the size of the ID of the Employee %d\n", i   1);
        int len;
        scanf("%d", &len);
        ids[i] = malloc(len   1);   // no need to cast the pointer, sizeof(char) is always 1

        printf("Enter Employee ID of Employee %d\n", i   1);
        scanf("%s", ids[i]);   // use fgets here
    }

    for (int i = 0; i < 3; i  )
    {
        printf("ID of Employee %d is %s\n", i   1, ids[i]);
        free(ids[i]);   // free it when you are done with it
    }

    return 0;
}```