c语言实现CGI通讯录

CGI（Common Gateway Interface）是一种常见的Web编程技术，可以让Web服务器调用外部程序实现动态网页。本文将介绍如何使用C语言实现一个简单的通讯录管理系统。

首先，需要在Web服务器上配置好CGI环境。这里以Apache服务器为例，可以在httpd.conf文件中添加如下配置：

ScriptAlias /cgi-bin/ "/usr/local/apache2/cgi-bin/"
<Directory "/usr/local/apache2/cgi-bin">
    AllowOverride None
    Options None
    Require all granted
</Directory>

这样，可以将CGI程序存放在/usr/local/apache2/cgi-bin目录下，并在Web页面中通过访问http://localhost/cgi-bin/program.cgi的方式调用程序。

接下来，编写C语言代码实现通讯录管理系统。这里使用了文件存储数据，因此需要先创建一个contacts.txt文件存放通讯录信息。

程序主要分为两部分：解析HTTP请求和处理通讯录操作。在解析HTTP请求时，需要读取请求方法、请求路径和请求参数等信息，然后根据请求路径调用相应的处理函数。在处理通讯录操作时，需要读取contacts.txt文件中的数据，并根据请求参数进行增删改查等操作。

以下是示例代码：

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

#define MAX_LINE 1024

// 解析HTTP请求
void parse_request(char *request_method, char *request_path, char *request_params) {
    char *request_body = getenv("QUERY_STRING");
    if (request_body == NULL) {
        request_method[0] = '\0';
        request_path[0] = '\0';
        request_params[0] = '\0';
        return;
    }
    sscanf(request_body, "%[^&]&%[^&]&%s", request_method, request_path, request_params);
}

// 处理添加联系人操作
void add_contact(char *params) {
    FILE *fp;
    char line[MAX_LINE];

    fp = fopen("contacts.txt", "a");
    if (fp == NULL) {
        printf("Content-type: text/plain\n\n");
        printf("Failed to open file\n");
        return;
    }

    sprintf(line, "%s\n", params);
    fputs(line, fp);
    fclose(fp);

    printf("Content-type: text/plain\n\n");
    printf("Success");
}

// 处理删除联系人操作
void delete_contact(char *params) {
    FILE *fp1, *fp2;
    char line[MAX_LINE];
    int found = 0;

    fp1 = fopen("contacts.txt", "r");
    if (fp1 == NULL) {
        printf("Content-type: text/plain\n\n");
        printf("Failed to open file\n");
        return;
    }

    fp2 = fopen("temp.txt", "w");
    if (fp2 == NULL) {
        printf("Content-type: text/plain\n\n");
        printf("Failed to open file\n");
        fclose(fp1);
        return;
    }

    while (fgets(line, MAX_LINE, fp1) != NULL) {
        if (strstr(line, params) == NULL) {
            fputs(line, fp2);
        } else {
            found = 1;
        }
    }

    fclose(fp1);
    fclose(fp2);

    if (found) {
        remove("contacts.txt");
        rename("temp.txt", "contacts.txt");

        printf("Content-type: text/plain\n\n");
        printf("Success");
    } else {
        remove("temp.txt");

        printf("Content-type: text/plain\n\n");
        printf("Contact not found");
    }
}

// 处理修改联系人操作
void update_contact(char *params) {
    FILE *fp1, *fp2;
    char line[MAX_LINE];
    int found = 0;

    fp1 = fopen("contacts.txt", "r");
    if (fp1 == NULL) {
        printf("Content-type: text/plain\n\n");
        printf("Failed to open file\n");
        return;
    }

    fp2 = fopen("temp.txt", "w");
    if (fp2 == NULL) {
        printf("Content-type: text/plain\n\n");
        printf("Failed to open file\n");
        fclose(fp1);
        return;
    }

    while (fgets(line, MAX_LINE, fp1) != NULL) {
        if (strstr(line, params) == NULL) {
            fputs(line, fp2);
        } else {
            found = 1;
            sprintf(line, "%s\n", params);
            fputs(line, fp2);
        }
    }

    fclose(fp1);
    fclose(fp2);

    if (found) {
        remove("contacts.txt");
        rename("temp.txt", "contacts.txt");

        printf("Content-type: text/plain\n\n");
        printf("Success");
    } else {
        remove("temp.txt");

        printf("Content-type: text/plain\n\n");
        printf("Contact not found");
    }
}

// 处理查询联系人操作
void query_contact(char *params) {
    FILE *fp;
    char line[MAX_LINE];
    int found = 0;

    fp = fopen("contacts.txt", "r");
    if (fp == NULL) {
        printf("Content-type: text/plain\n\n");
        printf("Failed to open file\n");
        return;
    }

    while (fgets(line, MAX_LINE, fp) != NULL) {
        if (strstr(line, params) != NULL) {
            printf("Content-type: text/plain\n\n");
            printf("%s", line);
            found = 1;
            break;
        }
    }

    fclose(fp);

    if (!found) {
        printf("Content-type: text/plain\n\n");
        printf("Contact not found");
    }
}

int main() {
    char request_method[MAX_LINE], request_path[MAX_LINE], request_params[MAX_LINE];

    parse_request(request_method, request_path, request_params);

    // 根据请求路径调用相应的处理函数
    if (strcmp(request_path, "/add") == 0) {
        add_contact(request_params);
    } else if (strcmp(request_path, "/delete") == 0) {
        delete_contact(request_params);
    } else if (strcmp(request_path, "/update") == 0) {
        update_contact(request_params);
    } else if (strcmp(request_path, "/query") == 0) {
        query_contact(request_params);
    } else {
        printf("Content-type: text/plain\n\n");
        printf("Invalid request");
    }

    return 0;
}

编译并将程序命名为program.cgi，然后将其存放在/usr/local/apache2/cgi-bin目录下。此时，在Web页面中访问http://localhost/cgi-bin/program.cgi/add?name=John&phone=123456789即可添加联系人，访问http://localhost/cgi-bin/program.cgi/query?name=John即可查询联系人信息，以此类推。