C：使用字符串数组时的空白输出

Question

So i tried to create a username and password for admins using c languange, in the code here the index of array inpstring determines what is username and password, for even (and 0) numbers are username, and odd numbers are password.

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

void Listofadmins(int index, char inpstring[][50]){
    if(index == 0){
        strcpy(inpstring[0], "Carl01");
        strcpy(inpstring[1], "SVm6u&N591s2");
    } else if(index == 1){
        strcpy(inpstring[2], "Devoth754");
        strcpy(inpstring[3], "eeKS7@8%0@T6");
    } else if(index == 2){
        strcpy(inpstring[4], "David439");
        strcpy(inpstring[5], "l$z7eqV2aD00");
    } else if(index == 3){
        strcpy(inpstring[6], "Matt208");
        strcpy(inpstring[7], "h9Je2#Ri3or$");
    }
}

void main()
    {
    int j, k = 0, y = 1;
    char str[100][100];
    for(j = 0, k, y; j < 4; j++, k += 2, y += 2){
        listofadmins(j, str[10]);
        printf("%s\n%s", str[k], str[y]);
    }
}

When i tried to run the code, there is no output and just blank. I thought that the listofadmins function will copy the string in inpstring array to the main program array str. Did you know where is the problem?

Answer 1

A few issues...

1. Using a 2D array for this is problematic. Better to create a struct
2. Doing an if/else ladder in Listofadmins along with strcpy is needlessly complicated
3. Using fixed size char arrays instead of char * complicates things.

---

Here is some simplified code:

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

struct user {
    const char *user;
    const char *pw;
};

struct user users[] = {
    { "Carl01", "SVm6u&N591s2" },
    { "Devoth754", "eeKS7@8%0@T6" },
    { "David439", "l$z7eqV2aD00" },
    { "Matt208", "h9Je2#Ri3or$" }
};

int
main(void)
{

    for (size_t i = 0;  i < sizeof(users) / sizeof(users[0]);  ++i) {
        struct user *user = &users[i];
        printf("User: %s Pw: %s\n",user->user,user->pw);
    }

    return 0;
}

---

Here is the program output:

User: Carl01 Pw: SVm6u&N591s2
User: Devoth754 Pw: eeKS7@8%0@T6
User: David439 Pw: l$z7eqV2aD00
User: Matt208 Pw: h9Je2#Ri3or$

Answer 2

I changed the call parameters for 'listofadmins' to match the declariation of 'str' truning inpstring[][50] into inpstring[][100] . And when calling the function I removed the brackets after 'str' so str[10] into str .

The resulting code is this

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

void listofadmins(int index, char inpstring[][100]){
 if(index == 0){
     strcpy(inpstring[0], "Carl01");
     strcpy(inpstring[1], "SVm6u&N591s2");
 } else if(index == 1){
     strcpy(inpstring[2], "Devoth754");
     strcpy(inpstring[3], "eeKS7@8%0@T6");
 } else if(index == 2){
     strcpy(inpstring[4], "David439");
     strcpy(inpstring[5], "l$z7eqV2aD00");
 } else if(index == 3){
     strcpy(inpstring[6], "Matt208");
     strcpy(inpstring[7], "h9Je2#Ri3or$");
 }
}

void main()
{
int j, k = 0, y = 1;
char str[100][100];
for(j = 0, k, y; j < 4; j++, k += 2, y += 2){
    listofadmins(j, str);
    printf("%s\n%s", str[k], str[y]);
}
}

The output is:

Carl01
SVm6u&N591s2Devoth754
eeKS7@8%0@T6David439
l$z7eqV2aD00Matt208
h9Je2#Ri3or$

I may recommend to change the printf for better readabilty. Hope i could help.