Common Gateway Interface如雷贯耳，遗憾的是一直以来都没玩过CGI，今天尝试一把。Tomcat可以是玩CGI的，但得改下配置。为了方便，直接使用一款更轻量级的web服务器lighttpd来跑，。
先把lighttpd安装一下：直接使用linux的包管理器，先安装一个epel软件仓库
yum install epel-release
从这个仓库里拿到lighttpd并安装
yum install lighttpd
安装好web服务器后就可以来写CGI代码了，可以用各种语言来写，这里选择C。C编译后本身就是可执行文件，所以我们得把CGI的配置改一改：
[root@iZbp11ahvmlfioymoo7u3bZ ~]# vi /etc/lighttpd/conf.d/cgi.conf #######################################################################
##
## CGI modules
## ---------------
##
## See https://redmine.lighttpd.net/projects/lighttpd/wiki/docs_modcgi
##
server.modules += ( "mod_cgi" ) ##
## Plain old CGI handling
##
## For PHP don't forget to set cgi.fix_pathinfo = 1 in the php.ini.
##
cgi.assign = ( ".pl" => "/usr/bin/perl",
".cgi" => "/usr/bin/perl",
".rb" => "/usr/bin/ruby",
".erb" => "/usr/bin/eruby",
".py" => "/usr/bin/python" ) ##
## to get the old cgi-bin behavior of apache
##
## Note: make sure that mod_alias is loaded if you uncomment the
## next line. (see modules.conf)
##
#alias.url += ( "/cgi-bin" => server_root + "/cgi-bin" )
#$HTTP["url"] =~ "^/cgi-bin" {
# cgi.assign = ( "" => "" )
#} ##
#######################################################################
这里将.cgi改为
".cgi" => "",
以上表示指定解析程序为空，这样对于带扩展名为.cgi的请求，不需要特定解析程序（比如用/bin/sh/perl）就能执行CGI。接着到/var/www/lighttpd目录，用C写一个简单例子
// A "hello world" page
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INCR_LEN 10 char *getValue(char *, char **);// get the param value
char **getParameters(char *, char **);// get the array of params and values
int main(void)
{
char **pQuery;
char *pParam;
char *name;
char *city;
pParam = getenv("QUERY_STRING");
char *pStr = malloc(strlen(pParam)+);
memcpy(pStr, pParam, strlen(pParam)+);
pQuery = getParameters(pStr, pQuery);
name = getValue("name", pQuery);
city = getValue("city", pQuery); printf("Content-Type:text/html\n\n");// print html
puts("<html>");
puts("<head><title>An HTML Page From a CGI</title></head>");
puts("<body><br>");
puts("<p><h2>Hello world!</h2></p>");
printf("<p>Your name is :%s</p>\n", name);
printf("<p>Your city is :%s</p>\n", city);
puts("</body>");
puts("</html>"); return ;
} char **getParameters(char *pTemp, char **pQuery)
{
char **pArrayTemp = NULL;
pQuery = calloc(INCR_LEN, sizeof(char *));
char *pParamIndex = NULL;
int i = ;
int count_max = INCR_LEN; while((pParamIndex = strchr(pTemp,'&')) != NULL)
{
if(i == count_max) // array reach max(10) need more memory
{
count_max += INCR_LEN;
pArrayTemp = realloc(pQuery, count_max*sizeof(char*));
if(!pArrayTemp)
{
exit();
}
pQuery = pArrayTemp;
} *(pQuery+i) = malloc(pParamIndex - pTemp + );
strncpy(*(pQuery+i), pTemp, pParamIndex - pTemp);
strncpy(pTemp, pParamIndex+, strlen(pTemp) - (pParamIndex-pTemp) + );
i++;
}
*(pQuery+i) = malloc(strlen(pTemp) + );
strncpy(*(pQuery+i), pTemp, strlen(pTemp)+);
return pQuery;
} char *getValue(char *pParameter, char **pParamValues)
{
char *pValue = NULL;
for(; *pParamValues!=NULL; pParamValues++)
{
if(strstr(*pParamValues, pParameter))
{
pValue = strchr(*pParamValues, '=');
if(pValue)
return pValue+;
}
} return NULL;
}
把上面的C编译一下：
gcc hello.c -o hello.cgi
最后把端口号由80改为其他端口号如8089，避免启动时与原有端口冲突。
vi /etc/lighttpd/lighttpd.conf
找到server.port后，将80改为8089。接着启动lighttpd服务器：
systemctl start lighttpd
再看下是否已经启起来了：
systemctl status lighttpd
● lighttpd.service - Lightning Fast Webserver With Light System Requirements
Loaded: loaded (/usr/lib/systemd/system/lighttpd.service; disabled; vendor preset: disabled)
Active: active (running) since Thu -- :: CST; 2s ago
Main PID: (lighttpd)
CGroup: /system.slice/lighttpd.service
└─ /usr/sbin/lighttpd -D -f /etc/lighttpd/lighttpd.conf Apr :: iZbp11ahvmlfioywlf7u3bZ systemd[]: Started Lightning Fast Webserver With Light System Requirements.
Apr :: iZbp11ahvmlfioywlf7u3bZ lighttpd[]: -- ::: (network.c.) warning: please use server.use-ipv6 only for hostnames, not wi...Y changes
Apr :: iZbp11ahvmlfioywlf7u3bZ lighttpd[]: -- ::: (server.c.) can't have more connections than fds/2: 1024 1024
我们看到已经启动成功了，但提示要用ipv6的地址来访问，但我想用ipv4，所以把它改掉，再次/etc/lighttpd/lighttpd.conf -> 找到server.use-ipv6 = "enable" -> 将enable改为disable -> systemctl restart lighttpd
然后我们通过ip:8089/index.html访问lighttpd自带的欢迎页：
再去访问我们编译好的hello.cgi，发现页面可以访问，却啥都没有，浏览器把页面直接下载了而不是渲染出来。咋回事呢？原来这时候的cgi文件浏览器是无法解析的，必须要去modules.conf里打开cgi：vi /etc/lighttpd/modules.conf -> 找到 #include "conf.d/cgi.conf" -> 将前面的#号删掉 -> 重启lighttpd systemctl restart lighttpd
再次访问我们的hello.cgi，这次ok了
