三、CGI编程实例
本节将用VB编写一个处理主页客户留言簿的CGI程序。除了要调用本文前面所介绍的Win32API函数外，程序中还调用了Win32API函数GetTempFileName()来获得一个唯一的临时文件名。程序中的函数UrlDecode()用来对客户端的输入进行URL译码。函数GetCgiValue()则用来分解字符串，根据表单元素的NAME属性获取其VALUE值，并调用UrlDecode()函数对其进行URL译码。
（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/bianchengyuyan/）本程序要求在留言簿文件guests.html中使用一个定位串! ENDHEAD ，将文件的开始部分和具体的客户留言部分分开。CGI程序将在! ENDHEAD 所在的位置插入客户新的留言。guests.html应具有如下所示的样式：
html headtitleDHTML Zone /title/head body bgcolor="#FFFFFF" text="#00000" vlink="#990000" link="#333399" ! ENDHEAD !---客户的留言部分从这开始-- P. !---客户的留言部分结束于此-- /body/html 这种样式将保证最后的留言出现在留言簿的最前面。如果要想使最后的留言出现在留言簿的最后面，则只需将留言簿文件中的定位字符串! ENDHEAD 移到留言簿文件中客户留言部分和HTML文件结尾部分之间的位置就行了。整个程序的完整代码如下所示： 注释：guestbook.bas Declare Function GetStdHandle Lib "kernel32" (ByVal nStdHandle As Long) As Long Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any,ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, lpOverlapped As Any) As Long Declare Function WriteFile Lib "kernel32" (ByVal hFile As Long,ByVal lpBuffer As String, ByVal nNumberOfBytesToWrite As Long,lpNumberOfBytesWritten As Long, lpOverlapped As Any) As Long Declare Function GetTempFileName Lib "kernel32" Alias "GetTempFileNameA"(ByVal lpszPath As String, ByVal lpPrefixString As String, ByVal wUnique As Long, ByVal lpTempFileName As String) As Long Public Const STD_INPUT_HANDLE = -10& Public Const STD_OUTPUT_HANDLE = -11& Public Const FILE_BEGIN = 0& Public hStdIn As Long 注释： 标准输入文件句柄 Public hStdOut As Long 注释： 标准输出文件句柄 Public sFormData As String 注释： 用于存储没有经过URL译码的用户输入数据 Public lContentLength As Long Public CGI_RequestMethod As String Sub Main() Dim CGI_ContentLength As String, CGI_QueryString As String, sBuff As String, chinesetail As String Dim lBytesRead As Long， rc As Long，I As Long Dim sEmail As String, sName As String, sURL As String, sfrom As String, tempstring As String Dim sComment As String, tempFileName As String, guestbook As String 注释：CGI程序的初始化工作 hStdIn = GetStdHandle(STD_INPUT_HANDLE) hStdOut = GetStdHandle(STD_OUTPUT_HANDLE) CGI_RequestMethod = Environ("REQUEST_METHOD") CGI_QueryString = Environ("QUERY_STRING") CGI_ContentLength = Environ("CONTENT_LENGTH") lContentLength = Val(CGI_ContentLength) sBuff = String(lContentLength, Chr$(0)) OutPut "Content-type: text/html" & vbCrLf 注释： 输出MIME类型 OutPut "FONT SIZE=""+2""" If CGI_RequestMethod = "POST" Then sBuff = String(lContentLength, Chr$(0)) rc = ReadFile(hStdIn, ByVal sBuff, lContentLength, lBytesRead, ByVal 0&) sFormData = Left$(sBuff, lBytesRead) ElseIf CGI_RequestMethod = "GET" Then sFormData = CGI_QueryString Else OutPut "Unknow Form Method !" End If chinesetail = String(400, " ") 注释：为了在页面上正确显示中文，生成一个空格串以获取客户端用户的输入 sName = GetCgiValue("name") sEmail = GetCgiValue("email") sURL = GetCgiValue("URL") sfrom = GetCgiValue("from") sComment = GetCgiValue("URL_Comment") 注释：对客户端用户的输入进行检查 If Len(sName) = 0 Then OutPut "P非常抱歉！您还没有填写姓名！" & chinesetail Exit Sub End If If Len(sComment) = 0 Then OutPut "P非常抱歉！您还没有提出建议！" & chinesetail Exit Sub End If 注释：获取唯一的临时文件名和留言簿文件并打开它们 tempFileName = TempFile("c:windowstemp", "gbk") guestbook = "e:netscapeserverdocsguests.html" Open tempFileName For Output As #1 Open guestbook For Input As #2 Do 注释：本循环体用于将留言簿中字符串"! ENDHEAD "前面的内容写入临时文件 Line Input #2, tempstring Print #1, tempstring Loop While tempstring "! ENDHEAD " And Not EOF(2) 注释：向临时文件中插入客户端用户的留言 Print #1, "hr" & vbCrLf Print #1, "ul" & vbCrLf Print #1, "lib留言时间/b：" & Date$ & " " & Time$ & vbCrLf Print #1, "lib姓名: /b" & sName & vbCrLf If Len(sEmail) 0 Then Print #1, "libE-mail: /ba href=""mailto:" & sEmail & """ " & sEmail & "/a" & vbCrLf End If If Len(sURL) 0 Then Print #1, "lib我的主页: /b a href=""" & sURL & """ " & sURL & "/a" & vbCrLf End If If Len(sfrom) 0 Then Print #1, "lib我来自: /b" & sfrom & vbCrLf End If Print #1, "lib我的建议: /b" & vbCrLf Print #1, sComment & vbCrLf Print #1, "/ul" & vbCrLf Do 注释：本循环体用于将留言簿剩余的东西写入留言簿 Line Input #2, tempstring Print #1, tempstring Loop While Not EOF(2) Close #1 Close #2 Kill guestbook 注释：删除旧的留言簿 Name tempFileName As guestbook 注释：将临时文件改成新的留言簿 OutPut "P非常感谢您的留言!" & chinesetail OutPut "P欢迎您经常光顾本主页！" & chinesetail OutPut "/FONT" End Sub Sub OutPut(s As String) 注释： 本子程序用于向标准输出写信息 Dim lBytesWritten As Long s = s & vbCrLf WriteFile hStdOut, s, Len(s), lBytesWritten, ByVal 0& End Sub Public Function GetCgiValue(cgiName As String) As String 注释： 本子程序可以获取表单上某一元素的数据 Dim delim2 As Long 注释： position of "=" Dim delim1 As Long 注释： position of "&" Dim n As Integer Dim pointer1 As Long，pointer2 As Long，length As Long，length1 As Long Dim tmpstring1 As String，tmpstring2 As String pointer1 = 1 pointer2 = 1 delim2 = InStr(pointer2, sFormData, "=") pointer2 = delim2 + 1 Do length = delim2 - pointer1 tmpstring1 = Mid(sFormData, pointer1, length) delim1 = InStr(pointer1, sFormData, "&") pointer1 = delim1 + 1 length1 = delim1 - pointer2 If delim1 = 0 Then length1 = lContentLength + 1 - pointer2 If tmpstring1 = cgiName Then tmpstring2 = Mid$(sFormData, pointer2, length1) GetCgiValue = UrlDecode(tmpstring2) Exit Do End If If delim1 = 0 Then Exit Do End If delim2 = InStr(pointer2, sFormData, "=") pointer2 = delim2 + 1 Loop End Function Public Function UrlDecode(ByVal sEncoded As String) As String 注释： 本函数可以对用户输入的数据进行URL解码 Dim pointer As Long 注释： sEncoded position pointer Dim pos As Long 注释： position of InStr target Dim temp As String If sEncoded = "" Then Exit Function pointer = 1 Do 注释：本循环体用于将"+"转换成空格 pos = InStr(pointer, sEncoded, "+") If pos = 0 Then Exit Do Mid$(sEncoded, pos, 1) = " " pointer = pos + 1 Loop pointer = 1 Do 注释：本循环体用于将%XX转换成字符。对于两个连续的%XX，如果第一个%XX不是某些特指的Web系统保留字符，将把它们转换成汉字 pos = InStr(pointer, sEncoded, "%") If pos = 0 Then Exit Do temp = Chr$("&H" & (Mid$(sEncoded, pos + 1, 2))) If Mid(sEncoded, pos + 3, 1) = "%" And (temp ":") And (temp "/") _ And (temp "(") And (temp ")") And (temp ".") And (temp ",") _ And (temp ";") And (temp "%") Then Mid$(sEncoded, pos, 2) = Chr$("&H" & (Mid$(sEncoded, pos + 1, 2)) _ & (Mid$(sEncoded, pos + 4, 2))) sEncoded = Left$(sEncoded, pos) & Mid$(sEncoded, pos + 6) pointer = pos + 1 Else Mid$(sEncoded, pos, 1) = temp sEncoded = Left$(sEncoded, pos) & Mid$(sEncoded, pos + 3) pointer = pos + 1 End If Loop UrlDecode = sEncoded Exit Function End Function Public Function TempFile(sPath As String, sPrefix As String) As String 注释：本函数可以获得一个唯一的临时文件名 Dim x As Long，rc As Long TempFile = String(127, Chr$(0)) rc = GetTempFileName(sPath, sPrefix, ByVal 0&, TempFile) x = InStr(TempFile, Chr$(0)) If x 0 Then TempFile = Left$(TempFile, x - 1) End Function CGI程序guestbook.bas所要处理的表单如下所示： htmlheadtitle贵宾留言簿/title/head body h3贵宾留言簿测试/h3 form action="/cgi-bin/guest.exe" method="post" 您的姓名: input type="text" name="name"br 您的Email信箱: input type="text" name="email"br 您的主页的URL: input type="text" name="URL"br 您的建议:br textarea name="URL_Comment" rows=4 cols=30/textareabr 您来自: input type="text" name="from"br input type="submit" value=" 留言 " /form /body/html（本文来源于图老师网站，更多请访问https://m.tulaoshi.com/bianchengyuyan/）虽然目前已经有很多可以取代CGI且其性能较CGI要高的技术（例如ASP、ISAPI、NSAPI等），但使用它们时需要用到专门的知识和工具，并且利用这些技术所编制的程序只适用于特定的Web服务器或系统平台。考虑到CGI编程具有易用易学性、跨服务器平台特性等优点，因此，CGI程序还将在WWW上占有一席之地。
