how to use gets() function in dynamic memory allocation with structure in c

Question

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

struct data
{
    char name[100];
    int age;
};

int main()
{
    struct data *p;
    int i, n;
    printf("\nENTER THE SIZE OF STRUCTURE:");
    scanf("%d", &n);
    p = (struct data *)calloc(n, sizeof(struct data));

    if (n < 0 || p == NULL)
    {
        printf("\nSTUCTURE DOESNOT CREATED");
    }
    else
    {
        for (i = 0; i < n; i++)
        {
            printf("\nENTER THE INFO FOR %d STRUCTER", i + 1);
            printf("\nENTER THE NAME:");
            gets((p + i)->name);

            printf("\nENTER THE AGE:");
            scanf("%d", &(p + i)->age);
        }
        for (i = 0; i < n; i++)
        {
            printf("\n");
            printf("\n%d\t\t%s\t\t%d", i + 1, (p + i)->name, (p + i)->age);
        }
        free(p);
    }
}

can I use gets() function to store string in this above code I know I can store with scanf() but it will terminated after white spaces and the reference of this program https://www.programiz.com/c-programming/examples/structure-dynamic-memory-allocation

Do not use gets at all. This function is deprecated for use with older C standard revisions and is completely removed from the newer ones. You can use fgets though. — Eugene Sh.
– Eugene Sh., Commented May 20, 2022 at 14:37
"how to use gets()" - Simple: you don't; ever. Use fgets instead. First read how it works, then understand how it's different than gets, then adapt accordingly. — WhozCraig
– WhozCraig, Commented May 20, 2022 at 14:38
Read the secret rules about using scanf successfully that no one ever teaches. — Steve Summit
– Steve Summit, Commented May 20, 2022 at 15:10

chqrlie · Accepted Answer · 2022-05-21 08:08:33Z

2

how to use gets() function?

Do not use gets() for anything. This function is obsolete and cannot be used safely. Instead of gets((p + i)->name), you can write:

scanf(" %99[^\n]", p[i].name);

Note the initial space in the scanf format string: it tells scanf() to skip initial white space, which is necessary to consume the pending newline into the name field. Without this space, scanf("%99[^\n]", p[i].name); would fail and return 0 because no characters from stdin would match the conversion specification before the newline.

edited May 21, 2022 at 8:08

answered May 20, 2022 at 14:43

chqrlie

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4 Comments

Ayush Talesara Over a year ago

thanks for solution but their is any way we can use fgets()

chqrlie Over a year ago

Mixing fgets() and scanf() is tricky because scanf() typically leaves the newline pending in stdin and fgets() will read an empty line if called immediately after.

Steve Summit Over a year ago

@AyushTalesara It's barely possible to mix fgets and scanf in the same program, but it's at least twice as hard and twice as confusing as just using fgets everywhere, or using scanf everywhere.

chqrlie Over a year ago

@Darth-CodeX: the space is necessary to consume the pending newline left by the previous call to scanf(). Answer amended with an appropriate explanation.

Darth-CodeX · Accepted Answer · 2022-05-21 02:56:43Z

1

Never use gets() function it is obsolete.

Try using fgets()

fgets(p[i].name, sizeof(p[i].name), stdin);
p[i].name[strcspn(p[i].name, "\n")] = 0;

edited May 21, 2022 at 2:56

answered May 20, 2022 at 15:27

Darth-CodeX

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2 Comments

Jonathan Leffler Over a year ago

Use sizeof(p[i].name) instead of 99, which will also avoid the off-by-one error. You can safely specify the exact size of the array to fgets().

chqrlie Over a year ago

This does not work because scanf("%d",...) left a pending newline in stdin that will be read by fgets() as an empty line. Mixing scanf() and fgets() is tricky indeed.

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