C语言使用指针和malloc函数实例

// names3.c -- use pointers and malloc()
#include <stdio.h>
#include <string.h>   // for strcpy(), strlen()
#include <stdlib.h>   // for malloc(), free()
#define SLEN 81
struct namect {
    char * fname;  // using pointers
    char * lname;
    int letters;
};

void getinfo(struct namect *);        // allocates memory
void makeinfo(struct namect *);
void showinfo(const struct namect *);
void cleanup(struct namect *);        // free memory when done
char * s_gets(char * st, int n);

int main(void)
{
    struct namect person;

    getinfo(&person);
    makeinfo(&person);
    showinfo(&person);
    cleanup(&person);

    return 0;
}

void getinfo (struct namect * pst)
{
    char temp[SLEN];
    printf("Please enter your first name.\n");
    s_gets(temp, SLEN);
    // allocate memory to hold name
    pst->fname = (char *) malloc(strlen(temp) + 1);
    // copy name to allocated memory
    strcpy(pst->fname, temp);
    printf("Please enter your last name.\n");
    s_gets(temp, SLEN);
    pst->lname = (char *) malloc(strlen(temp) + 1);
    strcpy(pst->lname, temp);
}

void makeinfo (struct namect * pst)
{
    pst->letters = strlen(pst->fname) +
    strlen(pst->lname);
}

void showinfo (const struct namect * pst)
{
    printf("%s %s, your name contains %d letters.\n",
           pst->fname, pst->lname, pst->letters);
}

void cleanup(struct namect * pst)
{
    free(pst->fname);
    free(pst->lname);
}

char * s_gets(char * st, int n)
{
    char * ret_val;
    char * find;

    ret_val = fgets(st, n, stdin);
    if (ret_val)
    {
        find = strchr(st, '\n');   // look for newline
        if (find)                  // if the address is not NULL,
            *find = '\0';          // place a null character there
        else
            while (getchar() != '\n')
                continue;          // dispose of rest of line
    }
    return ret_val;
}