给我一个c语言实例：可以进行用户以及管理员登录；管理员可以管理快递信息，录入用户信息以及货架号，用户可以凭取货码领取快递，并且管理员可以记录快递领取记录，用户也可以查询并领取快递。

好的，以下是一个示例C语言代码，实现了用户和管理员的登录、快递信息管理、以及快递领取记录的记录和查询功能。注意，这只是一个简单的示例代码，实际应用中还需要进行完善和优化。

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

#define MAX_USERS 100
#define MAX_PACKAGES 1000

struct user {
    char username[20];
    char password[20];
    int isAdmin;
};

struct package {
    char shelf[20];
    char code[20];
    char owner[20];
    char status[20];
};

struct user users[MAX_USERS];
int numUsers = 0;
struct package packages[MAX_PACKAGES];
int numPackages = 0;

void addUser() {
    if (numUsers >= MAX_USERS) {
        printf("Too many users!\n");
        return;
    }

    printf("Enter username: ");
    scanf("%s", users[numUsers].username);

    printf("Enter password: ");
    scanf("%s", users[numUsers].password);

    printf("Is this user an admin? (0=no, 1=yes): ");
    scanf("%d", &users[numUsers].isAdmin);

    numUsers++;
}

void addPackage() {
    if (numPackages >= MAX_PACKAGES) {
        printf("Too many packages!\n");
        return;
    }

    printf("Enter shelf: ");
    scanf("%s", packages[numPackages].shelf);

    printf("Enter code: ");
    scanf("%s", packages[numPackages].code);

    printf("Enter owner: ");
    scanf("%s", packages[numPackages].owner);

    strcpy(packages[numPackages].status, "unclaimed");

    numPackages++;
}

void login() {
    char username[20];
    char password[20];

    printf("Enter username: ");
    scanf("%s", username);

    printf("Enter password: ");
    scanf("%s", password);

    int isAdmin = 0;
    for (int i = 0; i < numUsers; i++) {
        if (strcmp(users[i].username, username) == 0 && strcmp(users[i].password, password) == 0) {
            isAdmin = users[i].isAdmin;
            break;
        }
    }

    if (isAdmin) {
        printf("Welcome admin!\n");
        printf("1. Add user\n");
        printf("2. Add package\n");
        printf("3. View package status\n");
        printf("4. Exit\n");

        int choice;
        scanf("%d", &choice);

        switch (choice) {
        case 1:
            addUser();
            break;
        case 2:
            addPackage();
            break;
        case 3:
            printf("Enter package code: ");
            char code[20];
            scanf("%s", code);

            struct package *p = NULL;
            for (int i = 0; i < numPackages; i++) {
                if (strcmp(packages[i].code, code) == 0) {
                    p = &packages[i];
                    break;
                }
            }

            if (p != NULL) {
                printf("Shelf: %s\n", p->shelf);
                printf("Owner: %s\n", p->owner);
                printf("Status: %s\n", p->status);
            } else {
                printf("Package not found!\n");
            }
            break;
        case 4:
            printf("Goodbye!\n");
            exit(0);
        default:
            printf("Invalid choice!\n");
        }
    } else {
        printf("Welcome user!\n");
        printf("1. Claim package\n");
        printf("2. Exit\n");

        int choice;
        scanf("%d", &choice);

        switch (choice) {
        case 1:
            printf("Enter package code: ");
            char code[20];
            scanf("%s", code);

            struct package *p = NULL;
            for (int i = 0; i < numPackages; i++) {
                if (strcmp(packages[i].code, code) == 0) {
                    p = &packages[i];
                    break;
                }
            }

            if (p != NULL && strcmp(p->status, "unclaimed") == 0) {
                strcpy(p->status, "claimed");
                printf("Package claimed!\n");
            } else {
                printf("Package not found or already claimed!\n");
            }
            break;
        case 2:
            printf("Goodbye!\n");
            exit(0);
        default:
            printf("Invalid choice!\n");
        }
    }
}

int main() {
    while (1) {
        printf("1. Login\n");
        printf("2. Exit\n");

        int choice;
        scanf("%d", &choice);

        switch (choice) {
        case 1:
            login();
            break;
        case 2:
            printf("Goodbye!\n");
            exit(0);
        default:
            printf("Invalid choice!\n");
        }
    }

    return 0;
}