boa我的配置：/etc/boa$ sudo vi boa.conf

# 下面几个都是关键点，基本就错这几个点上
# cumentRoot /var/www
#将cgi保存的实际位置和网站地址做个对应
# ScriptAlias /cgi-bin/ /var/www/cgi-bin/
#cgi脚本运行时能看到的$PATH（可选）
# CGIPath /bin:/usr/bin:/usr/local/bin
#如果想在任何位置都能运行cgi，要添加这个（可选）
AddType application/x-httpd-cgi cgi
# Boa v0.94 configuration file
# File format has not changed from 0.93
# File format has changed little from 0.92
# version changes are noted in the comments
#
# The Boa configuration file is parsed with a lex/yacc or flex/bison
# generated parser.  If it reports an error, the line number will be
# provided; it should be easy to spot.  The syntax of each of these
# rules is very simple, and they can occur in any order.  Where possible
# these directives mimic those of NCSA httpd 1.3; I saw no reason to 
# introduce gratuitous differences.

# $Id: boa.conf,v 1.25 2002/03/22 04:33:09 jnelson Exp $
# The "ServerRoot" is not in this configuration file.  It can be compiled
# into the server (see defines.h) or specified on the command line with
# the -c option, for example:
#
# boa -c /usr/local/boa

# Port: The port Boa runs on.  The default port for http servers is 80.

# If it is less than 1024, the server must be started as root.
# 端口老是被占用，所以我改掉了
Port 88

# Listen: the Internet address to bind(2) to.  If you leave it out,
# it takes the behavior before 0.93.17.2, which is to bind to all
# addresses (INADDR_ANY).  You only get one "Listen" directive,
# if you want service on multiple IP addresses, you have three choices:
#    1. Run boa without a "Listen" directive
#       a. All addresses are treated the same; makes sense if the addresses
#          are localhost, ppp, and eth0.
#       b. Use the VirtualHost directive below to point requests to different
#          files.  Should be good for a very large number of addresses (web
#          hosting clients).
#    2. Run one copy of boa per IP address, each has its own configuration
#       with a "Listen" directive.  No big deal up to a few tens of addresses.
#       Nice separation between clients.
# The name you provide gets run through inet_aton(3), so you have to use dotted
# quad notation.  This configuration is too important to trust some DNS.

#Listen 192.68.0.5
#  User: The name or UID the server should run as.
# Group: The group name or GID the server should run as.

User 0 
Group 0 

# ServerAdmin: The email address where server problems should be sent.
# Note: this is not currently used, except as an environment variable
# for CGIs.
#ServerAdmin root@localhost
# ErrorLog: The location of the error log file. If this does not start
# with /, it is considered relative to the server root.
# Set to /dev/null if you don't want errors logged.
# If unset, defaults to /dev/stderr

ErrorLog /var/log/boa/error_log

# Please NOTE: Sending the logs to a pipe ('|'), as shown below,
#  is somewhat experimental and might fail under heavy load.
# "Usual libc implementations of printf will stall the whole
#  process if the receiving end of a pipe stops reading."
#ErrorLog "|/usr/sbin/cronolog --symlink=/var/log/boa/error_log /var/log/boa/error-%Y%m%d.log"

# AccessLog: The location of the access log file. If this does not
# start with /, it is considered relative to the server root.
# Comment out or set to /dev/null (less effective) to disable 
# Access logging.
# AccessLog /var/log/boa/access_log
# Please NOTE: Sending the logs to a pipe ('|'), as shown below,
#  is somewhat experimental and might fail under heavy load.
# "Usual libc implementations of printf will stall the whole
#  process if the receiving end of a pipe stops reading."
#AccessLog  "|/usr/sbin/cronolog --symlink=/var/log/boa/access_log /var/log/boa/access-%Y%m%d.log"

# UseLocaltime: Logical switch.  Uncomment to use localtime 
# instead of UTC time
#UseLocaltime

# VerboseCGILogs: this is just a logical switch.
#  It simply notes the start and stop times of cgis in the error log
# Comment out to disable.

#VerboseCGILogs

# ServerName: the name of this server that should be sent back to 
# clients if different than that returned by gethostname + gethostbyname 

ServerName www.your.org.here

# VirtualHost: a logical switch.
# Comment out to disable.
# Given DocumentRoot /var/www, requests on interface 'A' or IP 'IP-A'
# become /var/www/IP-A.
# Example: http://localhost/ becomes /var/www/127.0.0.1
#
# Not used until version 0.93.17.2.  This "feature" also breaks commonlog
# output rules, it prepends the interface number to each access_log line.
# You are expected to fix that problem with a postprocessing script.

#VirtualHost 

# DocumentRoot: The root directory of the HTML documents.
# Comment out to disable server non user files.

DocumentRoot /var/www

# UserDir: The name of the directory which is appended onto a user's home
# directory if a ~user request is recieved.

UserDir public_html

# DirectoryIndex: Name of the file to use as a pre-written HTML
# directory index.  Please MAKE AND USE THESE FILES.  On the
# fly creation of directory indexes can be _slow_.
# Comment out to always use DirectoryMaker

DirectoryIndex index.html

# DirectoryMaker: Name of program used to create a directory listing.
# Comment out to disable directory listings.  If both this and
# DirectoryIndex are commented out, accessing a directory will give
# an error (though accessing files in the directory are still ok).

DirectoryMaker /usr/lib/boa/boa_indexer

# DirectoryCache: If DirectoryIndex doesn't exist, and DirectoryMaker
# has been commented out, the the on-the-fly indexing of Boa can be used
# to generate indexes of directories. Be warned that the output is 
# extremely minimal and can cause delays when slow disks are used.
# Note: The DirectoryCache must be writable by the same user/group that 
# Boa runs as.

# DirectoryCache /var/spool/boa/dircache

# KeepAliveMax: Number of KeepAlive requests to allow per connection
# Comment out, or set to 0 to disable keepalive processing

KeepAliveMax 1000

# KeepAliveTimeout: seconds to wait before keepalive connection times out

KeepAliveTimeout 10

# MimeTypes: This is the file that is used to generate mime type pairs
# and Content-Type fields for boa.
# Set to /dev/null if you do not want to load a mime types file.
# Do *not* comment out (better use AddType!)

MimeTypes /etc/mime.types

# DefaultType: MIME type used if the file extension is unknown, or there
# is no file extension.

DefaultType text/plain

# CGIPath: The value of the $PATH environment variable given to CGI progs.

CGIPath /bin:/usr/bin:/usr/local/bin

# SinglePostLimit: The maximum allowable number of bytes in 
# a single POST.  Default is normally 1MB.

# AddType: adds types without editing mime.types
# Example: AddType type extension [extension ...]

# Uncomment the next line if you want .cgi files to execute from anywhere
#AddType application/x-httpd-cgi cgi

# Redirect, Alias, and ScriptAlias all have the same semantics -- they
# match the beginning of a request and take appropriate action.  Use
# Redirect for other servers, Alias for the same server, and ScriptAlias
# to enable directories for script execution.

# Redirect allows you to tell clients about documents which used to exist in
# your server's namespace, but do not anymore. This allows you to tell the
# clients where to look for the relocated document.
# Example: Redirect /bar http://elsewhere/feh/bar

# Aliases: Aliases one path to another.
# Example: Alias /path1/bar /path2/foo

Alias /doc /usr/doc

# ScriptAlias: Maps a virtual path to a directory for serving scripts
# Example: ScriptAlias /htbin/ /www/htbin/

ScriptAlias /cgi-bin/ /var/www/cgi-bin/

Apache的cgi我的配置：sudo vi /etc/apache2/sites-enabled/000-default

   ServerName 127.0.0.1                                                        
   <VirtualHost *:80>
       ServerAdmin webmaster@localhost
   
       DocumentRoot /var/www
       <Directory />
           Options FollowSymLinks
           AllowOverride None
       </Directory>
      <Directory /var/www/>
          Options Indexes FollowSymLinks MultiViews
          AllowOverride None
          Order allow,deny
          allow from all
      </Directory>
 
      ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
      <Directory "/usr/lib/cgi-bin">
          AllowOverride None
          Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
          Order allow,deny                                                    
          Allow from all
      </Directory>
  
      ErrorLog ${APACHE_LOG_DIR}/error.log
  
      # Possible values include: debug, info, notice, warn, error, crit,
      # alert, emerg.
      LogLevel warn
  
      CustomLog ${APACHE_LOG_DIR}/access.log combined
  
      Alias /doc/ "/usr/share/doc/"
      <Directory "/usr/share/doc/">
          Options Indexes MultiViews FollowSymLinks
          AllowOverride None
          Order deny,allow
          Deny from all
          Allow from 127.0.0.0/255.0.0.0 ::1/128
      </Directory>
  
  </VirtualHost>  

都配好后运行 sudo ./boa
（ps：boa运行可传参 Usage: %s [-c serverroot] [-r chroot] [-d]
如不想后台运行可以追加 -d 即 sudo boa -d ）
访问 http://127.0.0.1:端口号
我的就是 http://127.0.0.1:88
gcc -o test.cgi test.c 编译生成 test.cgi
把cgi文件拷贝到 cgi-bin 下（我的目录是 /var/www/cgi-bin ）
网址就是 http://localhost:88/cgi-bin/test.cgi

下面提供几个测试代码，转自其他大佬，不过我找不到网址了。
1、

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

int main(void)
{
    char *data;
    long m,n;
    printf("Content-type:text/htmlnn");
    printf("<HTML>");
    printf("<HEAD>");
    printf("<TITLE>multi</TITLE>");
    printf("</HEAD>");
    printf("<BODY>");
    printf("<H2 ALIGN="center">multi control</H2>");
    printf("<FORM METHOD="GET" ACTION="test1.cgi">");
    printf("<P>Direction:<INPUT TYPE="text" NAME="m" VALUE="" size="18">");
    printf("<P>Step Number:<INPUT TYPE="text" NAME="n" VALUE="" size="17">");
    printf("<P ALIGN="left">");
    printf("<INPUT TYPE="SUBMIT"  VALUE="Submit">");
    printf("<INPUT TYPE="RESET"    VALUE="Reset">");
    printf("</P>");
    printf("</FORM>");
    printf("</BODY>");
    printf("</HTML>");

    data=getenv("QUERY_STRING");
    if(!data)
        printf("<P>get no datas and it's wrong.");
    else if(sscanf(data,"m=%ld&n=%ld",&m,&n)!=2)
        printf("<P>the input must be numbers");
    else
        printf("<P>%ld and %ld multi= %ld",m,n,m*n);
    return 0;
}

2、
/var/www 下的pass.html

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>用户登陆验证</title>
</head>
<body>
<form name="form1" action="/cgi-bin/pass.cgi" method="POST">
<table align="center">
    <tr><td align="center" colspan="2"></td></tr>
    <tr>
       <td align="right">用户名</td>
       <td><input type="text" name="Username"></td>
    </tr>
    <tr>
       <td align="right">密  码</td>
       <td><input type="password" name="Password"></td>
    </tr>
    <tr>
       <td><input type="submit" value="登  录"></td>
       <td><input type="reset" value="取  消"></td>
    </tr>
</table>
</form>
</body>
</html>

/var/www/cgi-bin 下的pass.c

/*=====================================================================
cgi例子
=====================================================================*/
//pass.c
#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];
       int i = 0;
       int j = 0;
      
//     printf("Content-type: text/plain; charset=iso-8859-1nn");
       printf("Content-type: text/htmlnn");
       printf("The following is query reuslt:<br><br>");
       req_method = getenv("REQUEST_METHOD");
       input = getcgidata(stdin, req_method);
       // 我们获取的input字符串可能像如下的形式
       // Username="admin"&Password="aaaaa"
       // 其中"Username="和"&Password="都是固定的
       // 而"admin"和"aaaaa"都是变化的，也是我们要获取的
      
       // 前面9个字符是UserName=
       // 在"UserName="和"&"之间的是我们要取出来的用户名
       for ( i = 9; i < (int)strlen(input); i++ )
       {
              if ( input[i] == '&' )
              {
                     name[j] = '';
                     break;
              }                  
              name[j++] = input[i];
       }
       // 前面9个字符 + "&Password="10个字符 + Username的字符数
       // 是我们不要的，故省略掉，不拷贝
       for ( i = 19 + strlen(name), j = 0; i < (int)strlen(input); i++ )
       {
              pass[j++] = input[i];
       }
       pass[j] = '';
       printf("Your Username is %s<br>Your Password is %s<br> n", name, pass);
      
       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] = '';
                     return input;
              }
             
              while(1)
              {
                     input[i] = (char)fgetc(fp);
                     if (i == size)
                     {
                            input[i+1] = '';
                            return input;
                     }
                    
                     --len;
                     if (feof(fp) || (!(len)))
                     {
                            i++;
                            input[i] = '';
                            return input;
                     }
                     i++;         
              }
       }
       return NULL;
}

效果图：

输入数据点击“登录”

自动跳转到 /cgi-bin/pass.cgi ,获取到数据并打印

你的配置会影响网址，502什么错误也是配置或权限有问题导致的。
如：
502 Bad Gateway
The CGI was not CGI/1.1 compliant.
cgi_header: unable to find LFLF
1.可能是网址打错了(路径是否和配置文件对应)
2.配置有问题
3.权限没给足 chmod 777 test.cgi
4.代码本身有问题（先测测 cgi-test.cgi）

提示“保存文件”

是直接运行的网页，地址不对，改成 http://localhost:886/config.html 即可。