Try   HackMD

Exercise 17

原始

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

#define MAX_DATA 512
#define MAX_ROWS 100

struct Address {
    int id;
    int set;
    char name[MAX_DATA];
    char email[MAX_DATA];
};

struct Database {
    struct Address rows[MAX_ROWS];
};

struct Connection {
    FILE *file;
    struct Database *db;
};

void die(const char *message)
{
    if (errno) {
        perror(message);
    } else {
        printf("ERROR: %s\n", message);
    }

    exit(1);
}

void Address_print(struct Address *addr)
{
    printf("%d %s %s\n", addr->id, addr->name, addr->email);
}

void Database_load(struct Connection *conn)
{
    int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
    if (rc != 1)
        die("Failed to load database.");
}

struct Connection *Database_open(const char *filename, char mode)
{
    struct Connection *conn = malloc(sizeof(struct Connection));
    if (!conn)
        die("Memory error");

    conn->db = malloc(sizeof(struct Database));
    if (!conn->db)
        die("Memory error");

    if (mode == 'c') {
        conn->file = fopen(filename, "w");
    } else {
        conn->file = fopen(filename, "r+");

        if (conn->file) {
            Database_load(conn);
        }
    }

    if (!conn->file)
        die("Failed to open the file");

    return conn;
}

void Database_close(struct Connection *conn)
{
    if (conn) {
        if (conn->file)
            fclose(conn->file);
        if (conn->db)
            free(conn->db);
        free(conn);
    }
}

void Database_write(struct Connection *conn)
{
    rewind(conn->file);

    int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
    if (rc != 1)
        die("Failed to write database.");

    rc = fflush(conn->file);
    if (rc == -1)
        die("Cannot flush database.");
}

void Database_create(struct Connection *conn)
{
    int i = 0;

    for (i = 0; i < MAX_ROWS; i++) {
        // make a prototype to initialize it
        struct Address addr = {.id = i, .set = 0};
        // then just assign it
        conn->db->rows[i] = addr;
    }
}

void Database_set(struct Connection *conn, int id, const char *name,
        const char *email)
{
    struct Address *addr = &conn->db->rows[id];
    if (addr->set)
        die("Already set, delete it first");

    addr->set = 1;
    // WARNING: bug, read the "How To Break It" and fix this
    char *res = strncpy(addr->name, name, MAX_DATA);
    // demonstrate the strncpy bug
    if (!res)
        die("Name copy failed");

    res = strncpy(addr->email, email, MAX_DATA);
    if (!res)
        die("Email copy failed");
}

void Database_get(struct Connection *conn, int id)
{
    struct Address *addr = &conn->db->rows[id];

    if (addr->set) {
        Address_print(addr);
    } else {
        die("ID is not set");
    }
}

void Database_delete(struct Connection *conn, int id)
{
    struct Address addr = {.id = id, .set = 0};
    conn->db->rows[id] = addr;
}

void Database_list(struct Connection *conn)
{
    int i = 0;
    struct Database *db = conn->db;

    for (i = 0; i < MAX_ROWS; i++) {
        struct Address *cur = &db->rows[i];

        if (cur->set) {
            Address_print(cur);
        }
    }
}

int main(int argc, char *argv[])
{
    if (argc < 3)
        die("USAGE: ex17 <dbfile> <action> [action params]");

    char *filename = argv[1];
    char action = argv[2][0];
    struct Connection *conn = Database_open(filename, action);
    int id = 0;

    if (argc > 3) id = atoi(argv[3]);
    if (id >= MAX_ROWS) die("There's not that many records.");

    switch (action) {
        case 'c':
            Database_create(conn);
            Database_write(conn);
            break;

        case 'g':
            if (argc != 4)
                die("Need an id to get");

            Database_get(conn, id);
            break;

        case 's':
            if (argc != 6)
                die("Need id, name, email to set");

            Database_set(conn, id, argv[4], argv[5]);
            Database_write(conn);
            break;

        case 'd':
            if (argc != 4)
                die("Need id to delete");

            Database_delete(conn, id);
            Database_write(conn);
            break;

        case 'l':
            Database_list(conn);
            break;
        default:
            die("Invalid action: c=create, g=get, s=set, d=del, l=list");
    }

    Database_close(conn);

    return 0;
}

這個程式的功能在建立一個基本聯絡資訊的資料庫 struct Database， 這個資料庫包含一個 element ： struct Address rows[MAX_ROWS]
struct Address 包含 int id 、 int set 、 char name[MAX_DATA] 、 char email[MAX_DATA] ， 其中 MAX_ROWS = 1000, MAX_DATA = 512 。
程式使用方式:

./ex17 <dbfile> <action> [action params]

 <dbfile> : 資料庫檔名
 <action> : 執行動作
     c : 建立資料庫
     g <id> : 取得某筆 id 的資料並印出
     s <id> <name> <email> ： 設定第 <id> 筆資料的內容
     d <id> : 刪除第 <id> 筆資料，這裡實作把 <set> 改為 0
     l : 列出所有建立的 Address
 [action params] ： 其他內容
     <action> 之後接的參數

Extra Credit

  • The die function needs to be augmented to let you pass the conn
    variable, so it can close it and clean up.
    –-> 完成

ex17_ext1


































































































































































































































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

#define MAX_DATA 512
#define MAX_ROWS 100

struct Address {
    int id;
    int set;
    char name[MAX_DATA];
    char email[MAX_DATA];
};

struct Database {
    struct Address rows[MAX_ROWS];
};

struct Connection {
    FILE *file;
    struct Database *db;
};

void Database_close(struct Connection *conn);

void die(const char *message, struct Connection *conn)
{
    if (errno) {
        if (conn) {
            Database_close(conn);
        }
        perror(message);
    } else {
        printf("ERROR: %s\n", message);
        if (conn) {
            Database_close(conn);
        }
    }

    exit(1);
}

void Address_print(struct Address *addr)
{
    printf("%d %s %s\n", addr->id, addr->name, addr->email);
}

void Database_load(struct Connection *conn)
{
    int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
    if (rc != 1)
        die("Failed to load database.", conn);
}

struct Connection *Database_open(const char *filename, char mode)
{
    struct Connection *conn = malloc(sizeof(struct Connection));
    if (!conn)
        die("Memory error", conn);

    conn->db = malloc(sizeof(struct Database));
    if (!conn->db)
        die("Memory error", conn);

    if (mode == 'c') {
        conn->file = fopen(filename, "w");
    } else {
        conn->file = fopen(filename, "r+");

        if (conn->file) {
            Database_load(conn);
        }
    }

    if (!conn->file)
        die("Failed to open the file", conn);

    return conn;
}

void Database_close(struct Connection *conn)
{
    if (conn) {
        if (conn->file)
            fclose(conn->file);
        if (conn->db)
            free(conn->db);
        free(conn);
    }
}

void Database_write(struct Connection *conn)
{
    rewind(conn->file);

    int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
    if (rc != 1)
        die("Failed to write database.", conn);

    rc = fflush(conn->file);
    if (rc == -1)
        die("Cannot flush database.", conn);
}

void Database_create(struct Connection *conn)
{
    int i = 0;

    for (i = 0; i < MAX_ROWS; i++) {
        // make a prototype to initialize it
        struct Address addr = {.id = i, .set = 0};
        // then just assign it
        conn->db->rows[i] = addr;
    }
}

void Database_set(struct Connection *conn, int id, const char *name,
        const char *email)
{
    struct Address *addr = &conn->db->rows[id];
    if (addr->set)
        die("Already set, delete it first", conn);

    addr->set = 1;
    // WARNING: bug, read the "How To Break It" and fix this
    char *res = strncpy(addr->name, name, MAX_DATA);
    // bug fixed 
    addr->name[MAX_DATA - 1] = '\0';
    // demonstrate the strncpy bug
    if (!res)
        die("Name copy failed", conn);

    res = strncpy(addr->email, email, MAX_DATA);
    if (!res)
        die("Email copy failed", conn);
    // bug fixed
    addr->email[MAX_DATA - 1] = '\0';
}

void Database_get(struct Connection *conn, int id)
{
    struct Address *addr = &conn->db->rows[id];

    if (addr->set) {
        Address_print(addr);
    } else {
        die("ID is not set", conn);
    }
}

void Database_delete(struct Connection *conn, int id)
{
    struct Address addr = {.id = id, .set = 0};
    conn->db->rows[id] = addr;
}

void Database_list(struct Connection *conn)
{
    int i = 0;
    struct Database *db = conn->db;

    for (i = 0; i < MAX_ROWS; i++) {
        struct Address *cur = &db->rows[i];

        if (cur->set) {
            Address_print(cur);
        }
    }
}

int main(int argc, char *argv[])
{
    if (argc < 3)
        die("USAGE: ex17 <dbfile> <action> [action params]", NULL);

    char *filename = argv[1];
    char action = argv[2][0];
    struct Connection *conn = Database_open(filename, action);
    int id = 0;

    if (argc > 3) id = atoi(argv[3]);
    if (id >= MAX_ROWS) die("There's not that many record.", conn);

    switch(action) {
        case 'c':
            Database_create(conn);
            Database_write(conn);
            break;

        case 'g':
            if (argc != 4)
                die("Need an id to get", conn);

            Database_get(conn, id);
            break;

        case 's':
            if (argc != 6)
                die("Need id, name, email to set", conn);

            Database_set(conn, id, argv[4], argv[5]);
            Database_write(conn);
            break;

        case 'd':
            if (argc != 4)
                die("Need id to delete", conn);

            Database_delete(conn, id);
            Database_write(conn);
            break;

        case 'l':
            Database_list(conn);
            break;
        default:
            die("Invalid action: c=create, g=get, s=set, d=del, l=list", conn);
    }

    Database_close(conn);

    return 0;
}
  • Change the code to accept parameters for MAX_DATA and MAX_ROWS,
    store them in the Database struct, and write that to the file, thus creating a database that can be arbitrarily sized.
    –> 嘗試調整 MAX_ROWS 使其變成可變的任意大小，但是在執行以下指令時出現 Segmentation Fault

ex17_ext2







































































































































































































































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

#define MAX_DATA 512
#define MAX_ROWS 100

struct Address {
    int id;
    int set;
    char name[MAX_DATA];
    char email[MAX_DATA];
};

struct Database {
    int max_rows;
    struct Address rows[];
};

struct Connection {
    FILE *file;
    struct Database *db;
};

void Database_close(struct Connection *conn);

void die(const char *message, struct Connection *conn)
{
    if (errno) {
        if (conn) {
            Database_close(conn);
        }
        perror(message);
    } else {
        printf("ERROR: %s\n", message);
        if (conn) {
            Database_close(conn);
        }
    }

    exit(1);
}

void Address_print(struct Address *addr)
{
    printf("%d %s %s\n", addr->id, addr->name, addr->email);
}

void Database_load(struct Connection *conn)
{
    int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
    if (rc != 1)
        die("Failed to load database.", conn);
}

struct Connection *Database_open(const char *filename, char mode, int max_rows)
{
    struct Connection *conn = malloc(sizeof(struct Connection));
    if (!conn)
        die("Memory error", conn);

    conn->db = malloc(sizeof(struct Database) + sizeof(char[max_rows]));
    if (!conn->db)
        die("Memory error", conn);

    if (mode == 'c') {
        conn->file = fopen(filename, "w");
    } else {
        conn->file = fopen(filename, "r+");

        if (conn->file) {
            Database_load(conn);
        }
    }

    if (!conn->file)
        die("Failed to open the file", conn);

    return conn;
}

void Database_close(struct Connection *conn)
{
    if (conn) {
        if (conn->file)
            fclose(conn->file);
        if (conn->db)
            free(conn->db);
        free(conn);
    }
}

void Database_write(struct Connection *conn)
{
    rewind(conn->file);

    int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
    if (rc != 1)
        die("Failed to write database.", conn);

    rc = fflush(conn->file);
    if (rc == -1)
        die("Cannot flush database.", conn);
}

void Database_create(struct Connection *conn, int max_rows)
{
    int i = 0;

    for (i = 0; i < max_rows; i++) {
        // make a prototype to initialize it
        struct Address addr = {.id = i, .set = 0};

        // then just assign it
        conn->db->rows[i] = addr;
    }
}

void Database_set(struct Connection *conn, int id, const char *name,
        const char *email)
{
    struct Address *addr = &conn->db->rows[id];
    if (addr->set)
        die("Already set, delete it first", conn);

    addr->set = 1;
    // WARNING: bug, read the "How To Break It" and fix this
    char *res = strncpy(addr->name, name, MAX_DATA);
    // bug fixed 
    addr->name[MAX_DATA - 1] = '\0';
    // demonstrate the strncpy bug
    if (!res)
        die("Name copy failed", conn);

    res = strncpy(addr->email, email, MAX_DATA);
    if (!res)
        die("Email copy failed", conn);
    // bug fixed
    addr->email[MAX_DATA - 1] = '\0';
}

void Database_get(struct Connection *conn, int id)
{
    struct Address *addr = &conn->db->rows[id];

    if (addr->set) {
        Address_print(addr);
    } else {
        die("ID is not set", conn);
    }
}

void Database_delete(struct Connection *conn, int id)
{
    struct Address addr = {.id = id, .set = 0};
    conn->db->rows[id] = addr;
}

void Database_list(struct Connection *conn)
{
    int i = 0;
    struct Database *db = conn->db;

    for (i = 0; i < MAX_ROWS; i++) {
        struct Address *cur = &db->rows[i];

        if (cur->set) {
            Address_print(cur);
        }
    }
}

int main(int argc, char *argv[])
{
    if (argc < 3)
        die("USAGE: ex17 <dbfile> <action> [action params]", NULL);

    char *filename = argv[1];
    char action = argv[2][0];

    // adding this to setting max_rows
    int max_rows = 10;
    struct Connection *conn = Database_open(filename, action, max_rows);
    int id = 0;

    if (argc > 3) id = atoi(argv[3]);
    if (id >= MAX_ROWS) die("There's not that many record.", conn);

    switch(action) {
        case 'c':
            Database_create(conn, max_rows);
            Database_write(conn);
            break;

        case 'g':
            if (argc != 4)
                die("Need an id to get", conn);

            Database_get(conn, id);
            break;

        case 's':
            if (argc != 6)
                die("Need id, name, email to set", conn);

            Database_set(conn, id, argv[4], argv[5]);
            Database_write(conn);
            break;

        case 'd':
            if (argc != 4)
                die("Need id to delete", conn);

            Database_delete(conn, id);
            Database_write(conn);
            break;

        case 'l':
            Database_list(conn);
            break;
        default:
            die("Invalid action: c=create, g=get, s=set, d=del, l=list", conn);
    }

    Database_close(conn);

    return 0;
}

$ ./ex17_ext2 db.dat c
Segmentation fault

與ext1比較，修改了：

$ diff ex17_ext1.c ex17_ext2.c
18c18,19
<     struct Address rows[MAX_ROWS];
---
>     int max_rows;
>     struct Address rows[];
57c58
< struct Connection *Database_open(const char *filename, char mode)
---
> struct Connection *Database_open(const char *filename, char mode, int max_rows)
63c64
<     conn->db = malloc(sizeof(struct Database));
---
>     conn->db = malloc(sizeof(struct Database) + sizeof(char[max_rows]));
107c108
< void Database_create(struct Connection *conn)
---
> void Database_create(struct Connection *conn, int max_rows)
111c112
<     for (i = 0; i < MAX_ROWS; i++) {
---
>     for (i = 0; i < max_rows; i++) {
113a115
> 
180c182,185
<     struct Connection *conn = Database_open(filename, action);
---
> 
>     // adding this to setting max_rows
>     int max_rows = 10;
>     struct Connection *conn = Database_open(filename, action, max_rows);
188c193
<             Database_create(conn);
---
>             Database_create(conn, max_rows);

使用gdb 把過程顯示出來

$ gdb --batch --ex run --ex bt --ex q --args ./ex17_ext2 db.dat c

Program received signal SIGSEGV, Segmentation fault.
0x0000007ff7eb1d88 in __GI_rewind (fp=0x55555632e0) at rewind.c:34
34	rewind.c: No such file or directory.
#0  0x0000007ff7eb1d88 in __GI_rewind (fp=0x55555632e0) at rewind.c:34
#1  0x0000005555550e3c in Database_write (conn=0x55555632a0) at ex17_ext2.c:97
#2  0x00000055555512d0 in main (argc=3, argv=0x7ffffff998) at ex17_ext2.c:194
A debugging session is active.

	Inferior 1 [process 1305537] will be killed.

Quit anyway? (y or n) [answered Y; input not from terminal]

錯誤發生在 Database_write 函式裡呼叫 rewind（） 這個處理 FILE 類內建函式把 steam 指向的位置重置為開頭時發生錯誤，但想好久還是不懂為什麼會錯，難道是 conn->file 這邊由 -> 讀取 file 時產生問題？
再仔細檢查，發現是自己打錯了!

conn->db = malloc(sizeof(struct Database) + sizeof(char[max_rows]));

應該改成

conn->db = malloc(sizeof(struct Database) + sizeof(struct Address[max_rows]));

由於參考 C99 規格書 在 6.7.2.1.16 FAM(Flexible Array Members) 時忘記改為正確的類型。
這讓我好奇，先回憶 struct Connection

struct Connection {
    FILE *file;
    struct Database *db;
};

有 FILE *file 及 struct Database *db
為什麼在 struct Connection conn 的成員 db 呼叫 malloc ，分配空間時輸入不對的類別，會造成後來使用 rewind 讀取 conn 的成員 file 時發生找不到的錯誤?

後來找到解答，由於前面分配錯的空間（ + sizeof(char[max_rows]），這樣是分配 max_rows 個 char 的空間，但是再回看 struct Database :

struct Database {
    int max_rows;
    struct Address rows[];
}

這邊rows是 struct Address type ， 所以儘管分配錯誤的空間大小 ( + sizeof(char[max_rows])) ，但是當存取 rows[i] 對應的 element 的時候，它會跳 i 個 struct Address type， 所以整個記憶體位置就不對了。
而實際看看問題出在哪裡：

./ex17_ext2 db.dat c

第一個參數 db.dat 代表一個檔案名稱，第二個參數 c 是產生第一個檔案，裡面存 MAX_ROWS 筆 struct Address，而這兩個參數在執行過程會依序呼叫 Database_open 、 Database_create 、 Database_write。而錯誤發生在 Database_write裡面的 rewind() ，經過 gdb 執行過程找到問題，是這樣產生的：

  1. 在 Database_open ，先 malloc 分配出可用記憶體空間給 conn ， 之後 malloc 分配空間給 conn->db ， 再來 fopen 建立 conn->file，
    在 gdb 裡顯示 conn 、 conn->db 、 conn->file 的記憶體位置，原先能正常執行時各個變數記憶體位置可能如下：
1: conn = (struct Connection *) 0x55555632a0
2: conn->db = (struct Database *) 0x55555632c0
3: conn->file = (FILE *) 0x555557c5f0

而分配錯誤空間後各個變數記憶體位置可能如下：

1: conn = (struct Connection *) 0x55555632a0
2: conn->db = (struct Database *) 0x55555632c0
3: conn->file = (FILE *) 0x55555632e0

可以看出前者 conn->file 的位置跟 conn->db 兩個變數的 差值 比 後者 兩個變數的差值還大，先是由於分配錯誤空間大小導致，這邊還沒有問題，問題發生在之後 conn->create 的時候用新產生的 struct Address assign 給 rows的時候，由此把 conn->file 的內容也改寫掉導致。
2. 由此也可觀察出 struct 裡 element 的位置其記憶體位址不一定從上到下，回看用 malloc 建立 conn->db 再建立 conn->file 可以看出 後者的記憶體位置是接在 conn->db 之後而不是之前。
最後放上能運行的：
ex17_ext2.c

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

#define MAX_DATA 512
#define MAX_ROWS 100

struct Address {
    int id;
    int set;
    char name[MAX_DATA];
    char email[MAX_DATA];
};

struct Database {
    int max_rows;
    struct Address rows[];
};

struct Connection {
    FILE *file;
    struct Database *db;
};

void Database_close(struct Connection *conn);

void die(const char *message, struct Connection *conn)
{
    if (errno) {
        if (conn) {
            Database_close(conn);
        }
        perror(message);
    } else {
        printf("ERROR: %s\n", message);
        if (conn) {
            Database_close(conn);
        }
    }

    exit(1);
}

void Address_print(struct Address *addr)
{
    printf("%d %s %s\n", addr->id, addr->name, addr->email);
}

void Database_load(struct Connection *conn, int max_rows)
{
    int rc = fread(conn->db, sizeof(struct Database) + sizeof(struct Address[max_rows]), 1, conn->file);
    if (rc != 1)
        die("Failed to load database.", conn);
}

struct Connection *Database_open(const char *filename, char mode, int max_rows)
{
    struct Connection *conn = malloc(sizeof(struct Connection));
    if (!conn)
        die("Memory error", conn);

    conn->db = malloc(sizeof(struct Database) + sizeof(struct Address[max_rows]));
    if (!conn->db)
        die("Memory error", conn);

    conn->db->max_rows = max_rows;

    if (mode == 'c') {
        conn->file = fopen(filename, "w");
    } else {
        conn->file = fopen(filename, "r+");

        if (conn->file) {
            Database_load(conn, max_rows);
        }
    }

    if (!conn->file)
        die("Failed to open the file", conn);

    return conn;
}

void Database_close(struct Connection *conn)
{
    if (conn) {
        if (conn->file)
            fclose(conn->file);
        if (conn->db)
            free(conn->db);
        free(conn);
    }
}

void Database_write(struct Connection *conn, int max_rows)
{
    rewind(conn->file);

    int rc = fwrite(conn->db, sizeof(struct Database) + sizeof(struct Address[max_rows]), 1, conn->file);
    if (rc != 1)
        die("Failed to write database.", conn);

    rc = fflush(conn->file);
    if (rc == -1)
        die("Cannot flush database.", conn);
}

void Database_create(struct Connection *conn, int max_rows)
{
    int i = 0;

    for (i = 0; i < max_rows; i++) {
        // make a prototype to initialize it
        struct Address addr = {.id = i, .set = 0};

        // then just assign it
        conn->db->rows[i] = addr;
    }
}

void Database_set(struct Connection *conn, int id, const char *name,
        const char *email)
{
    struct Address *addr = &conn->db->rows[id];
    if (addr->set)
        die("Already set, delete it first", conn);

    addr->set = 1;
    // WARNING: bug, read the "How To Break It" and fix this
    char *res = strncpy(addr->name, name, MAX_DATA);
    // bug fixed 
    addr->name[MAX_DATA - 1] = '\0';
    // demonstrate the strncpy bug
    if (!res)
        die("Name copy failed", conn);

    res = strncpy(addr->email, email, MAX_DATA);
    if (!res)
        die("Email copy failed", conn);
    // bug fixed
    addr->email[MAX_DATA - 1] = '\0';
}

void Database_get(struct Connection *conn, int id)
{
    struct Address *addr = &conn->db->rows[id];

    if (addr->set) {
        Address_print(addr);
    } else {
        die("ID is not set", conn);
    }
}

void Database_delete(struct Connection *conn, int id)
{
    struct Address addr = {.id = id, .set = 0};
    conn->db->rows[id] = addr;
}

void Database_list(struct Connection *conn, int max_rows)
{
    int i = 0;
    struct Database *db = conn->db;

    for (i = 0; i < max_rows; i++) {
        struct Address *cur = &db->rows[i];

        if (cur->set) {
            Address_print(cur);
        }
    }
}

int main(int argc, char *argv[])
{
    if (argc < 3)
        die("USAGE: ex17 <dbfile> <action> [action params]", NULL);

    char *filename = argv[1];
    char action = argv[2][0];

    // adding this to setting max_rows
    int max_rows = 10;
    struct Connection *conn = Database_open(filename, action, max_rows);
    int id = 0;

    if (argc > 3) id = atoi(argv[3]);
    if (id >= MAX_ROWS) die("There's not that many record.", conn);

    switch(action) {
        case 'c':
            Database_create(conn, max_rows);
            Database_write(conn, max_rows);
            break;

        case 'g':
            if (argc != 4)
                die("Need an id to get", conn);

            Database_get(conn, id);
            break;

        case 's':
            if (argc != 6)
                die("Need id, name, email to set", conn);

            Database_set(conn, id, argv[4], argv[5]);
            Database_write(conn, max_rows);
            break;

        case 'd':
            if (argc != 4)
                die("Need id to delete", conn);

            Database_delete(conn, id);
            Database_write(conn, max_rows);
            break;

        case 'l':
            Database_list(conn, max_rows);
            break;
        default:
            die("Invalid action: c=create, g=get, s=set, d=del, l=list", conn);
    }

    Database_close(conn);

    return 0;
}
Last changed by 
 
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