cgi程序读取post发送的特殊字符，尤其适合于微信公众平台开发中发送被动消息

【问题】用c编写cgi程序怎样取出html表单post来的数据？

【分析】html表单post来的数据形如username="zhang"&&password="123456"&&useid="012"

【方法1】lainco

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *getcgidata(FILE *fp, char *requestmethod);
int main()
{
    char *input;
    char *req_method;
    char name[64];
    char pass[64];
    char userid[64];
    int i = 0;
    int j = 0;
    // printf("Content-type: text/plain; charset=iso-8859-1\n\n");
    printf("Content-type: text/html\n\n");
    printf("The following is query reuslt:<br><br>");
    req_method = getenv("REQUEST_METHOD");
    input = getcgidata(stdin, req_method);

    for ( i = 9; i < (int)strlen(input); i++ )
    {
        if ( input[i] == '&' )
        {
            name[j] = '\0';
            break;
        }
        name[j++] = input[i];
    }

    for ( i = 19 + strlen(name), j = 0; i < (int)strlen(input); i++ )
    {
        if ( input[i] == '&' )
        {
            pass[j] = '\0';
            break;
        }
        pass[j++] = input[i];
    }

    for ( i = 30 + strlen(pass) + strlen(name), j = 0; i < (int)strlen(input); i++ )
    {
        userid[j++] = input[i];
    }

    userid[j] = '\0';
    printf("Your Username is %s<br>Your Password is %s<br>Your userid is %s<br> \n", name, pass, userid);
    return 0;
}
char *getcgidata(FILE *fp, char *requestmethod)
{
    char *input;
    int len;
    int size = 1024;
    int i = 0;
    if (!strcmp(requestmethod, "GET"))
    {
        input = getenv("QUERY_STRING");
        return input;
    }
    else if (!strcmp(requestmethod, "POST"))
    {
        len = atoi(getenv("CONTENT_LENGTH"));
        input = (char *)malloc(sizeof(char) * (size + 1));
        if (len == 0)
        {
            input[0] = '\0';
            return input;
        }
        while (1)
        {
            input[i] = (char)fgetc(fp);
            if (i == size)
            {
                input[i + 1] = '\0';
                return input;
            }
            --len;
            if (feof(fp) || (!(len)))
            {
                i++;
                input[i] = '\0';
                return input;
            }
            i++;
        }
    }
    return NULL;
}

【方法2】

1 先将post来的数据总体读入info

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1. char *info=NULL;
2. char username[64];
3. char passwd[64];
4. int userid;
5. int lenstr=0;
6. memset(username,0,64);
7. memset(passwd,0,64);
8. userid=0;
9. /*
10. * Get the data by post method from index.html
11. */
12. lenstr=atoi(getenv("CONTENT_LENGTH"));
13. info=(char *)malloc(lenstr+1);
14. fread(info,1,lenstr,stdin);

2 将info作为文件流输入。利用sscanf提取子串

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1. sscanf(info,"username=%[^&]&passwd=%[^&]&userid=%d",username,passwd,&userid);
2. free(info);

注：假设数据为实型。则利用sscanf时。要加上&，如上例userid

【思考】假设子串为username=zhang; passwd=123; userid=012，怎样用【方法2】提取？

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1. sscanf(info,"username=%[^;]; passwd=%[^;]; userid=%d",&username,&passwd,&userid);

注意：将%[^&]&替换为%[^;];。

通过本例，能够明确%[^;];的使用方法。

【解析】%[^&]是正則表達式，具体请參考：

uid=9195812&do=blog&cuid=499274" style="color:rgb(51,102,153); text-decoration:none">http://blog.chinaunix.net/space.php?uid=9195812&do=blog&cuid=499274