C程序-将字符串数组合并到程序中时出错

Question

I'm trying to write program to ask user to enter First and Last Name. Then my program will result their Full Name (combined First + Last Name) and the length of their Full Name. My Output right now does empty Full Name and 0 length. I guess my problem is at display_name functions. Here is my code so far. Thank you.

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

void display_name(char *fullname);

int count_char( char*x_ptr);    

char * get_name(char * first_name, char * last_name);

#define MAX 80     // maximum number of array elements 

int main(void)
{
    char first_name[MAX];
    char last_name[MAX];
    char *x_ptr; 

    system("cls");
    printf("Enter Last Name: \n" );
    scanf("%s", &last_name );
    printf("Enter First Name: \n" );
    scanf("%s", &first_name );

    x_ptr = get_name(first_name, last_name);

    display_name(x_ptr);

    puts("");                                    
    system("pause");                              
    return 0;                                                             
}

char * get_name(char *first_name, char *last_name)
{
    static char fullname[MAX];
    char x;
    x = 0;
    strcpy(fullname, first_name);
    strcat(fullname, " ");
    strcat(fullname, last_name);


    while (((fullname[x] = getchar()) != '\n') && (x < (MAX-1))) 
    {
            x++;                                          
    }
    fullname[x] = '\0';     
    return(fullname); 

}
/* Function to print out string passed to it and display the length of fullname*/
void display_name(char *fullname)
{
    char *a;                                    
    printf("Your Full name is ");
    a = &fullname[0];                              
    while (*a != '\0')                              
      {
            putchar(*a);                              
            a++;                                    
      }

    int length;
    length  =  strlen(fullname); 
    printf("\nHas %d Characters",  length);  
    length = count_char(fullname);
    printf("\nHas %d Non Space Characters", length); 

}
/* function to return count of non space characters*/
int count_char( char * x_ptr)
{
        char *b;                                    
    unsigned int count=0;                        
    b = x_ptr;                                    
    while (*b != '\0')                              
    {
            if (*b != ' ')                        
                  count++;                        
            b++;                                    
    }
return
(count);                              
}

Answer 1

scanf("%s", &last_name );

Compiler complained and you ignored it. It should be scanf("%s", last_name ); . Same goes with firstname . Yours had type char (*)[] and scanf expects char* which is what we gave in second case.

This part is doing nothing that you would do to achieve what you are trying to do.

while (((fullname[x] = getchar()) != '\n') && (x < (MAX-1))) 

This is using getchar to get the characters from stdin and put it in the char array where you are storing the concatenated name.

Using static char array is not a good solution. The next time you try to use this function - it will overwrite the data previously written by another function. Illustration implementation of the function get_name would be

char * get_name(char *first_name, char *last_name)
{
    char *fullname = malloc(strlen(first_name)+2+strlen(last_name));
    if(!fullname){
       perror("malloc");
       exit(EXIT_FAILURE);
    }
    strcpy(fullname, first_name);
    strcat(fullname, " ");
    strcat(fullname, last_name);
    return fullname;
}

Benefit of using this implementation is that - now the data that is being used is not closely coupled with the methods that call this one. So it can be reused independent of it's previous usage in another function.

Also when using the function get_name remember to free the dynamically allocated memory when you are done working with it.