Pointer structure

In the case of the structure with a pointer

#include<stdio.h>

struct man
{
    char *name;
    int age;
};

int main()
{
    struct man m = {"tom",20};
    printf("name = %s, age = %d\n",m.name,m.age);
    return 0;
}

operation result:

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot @ ubuntu: ~ / wangqinghe / C / 20190714 $ ./struct

name = tom, age = 20

If you modify the value of m.name

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

struct man
{
    char *name;
    int age;
};

int main()
{
    struct man m = {"tom",20};
    strcpy(m.name,"mike");
    printf("name = %s, age = %d\n",m.name,m.age);
    return 0;
}

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot @ ubuntu: ~ / wangqinghe / C / 20190714 $ ./struct

Segmentation fault (core dumped)

The above error.

Change the pointer bit array:

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

struct man
{
    char name[256];
    int age;
};

int main()
{
    struct man m = {"tom",20};
    strcpy(m.name,"mike");
    printf("name = %s, age = %d\n",m.name,m.age);
    return 0;
}

Compile and run:

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot @ ubuntu: ~ / wangqinghe / C / 20190714 $ ./struct

name = mike, age = 20

analysis:

Numerical constants in memory can not be modified.

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

struct man
{
    char *name;
    int age;
};

int main()
{
    //struct man m = {"tom",20};
    struct man m;
    m.name = malloc(sizeof(char) * 100);
    m.age = 20;
    strcpy(m.name,"mike");
    printf("name = %s, age = %d\n",m.name,m.age);
    return 0;
}

Compile and run:

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot @ ubuntu: ~ / wangqinghe / C / 20190714 $ ./struct

name = mike, age = 20

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

struct man
{
    char *name;
    int age;
};

int main()
{
    struct man *p = malloc(sizeof(struct man));
    p->name = malloc(sizeof(char) * 100);
    strcpy(p->name,"tom");
    p->age = 30;
    printf("name = %s, age = %d\n",p->name,p->age);
    free(p->name);
    free(p);
    return 0;
}

Pointer memory storage:

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot @ ubuntu: ~ / wangqinghe / C / 20190714 $ ./struct

name = tom, age = 30

END

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