Web Server Variables and CGI environment variables

accessing CGI environment- and Internet server variables from within a eDeveloper program

In order to pass data in a request from a CGI script, a web server uses the command line and envronment variables (according to the CGI specification). These variables then contain important information about the request and the client and you can access this information from within CGI scripts. In Magic & Internet applications which receive requests, you might want to access and use this information as well.

Examples for such information are f.i. the IP address of the client (REMOTE_ADDR) and the host name of the client (REMOTE_HOST).

If you protected your Magic & internet application with SSL and client certificates, you might want to get some information about the client and server certificate and decide if you accept or reject that request.

Similarly, Cookies are exchanged between http client (browser) and server (web server) by means of http header variables. Cookies will have been however already been disjointed by the requester for you. While the CGI environment variable 'HTTP_COOKIE' contains the complete cookie string, you can access the cookies by GetParam() with the name of a cookie as parameter. This works without having to define the name of the cookie as token in the HttpVars (find more information about HttpVars below).

Besides information about the client and the request, CGI also suggests that some information should be exposed as environment variables to CGI scripts which are not request specific. This is e.g. information about the installed server software, the protocol, ... Information you might want to use within your Magic & internet application as well (f.i. to find out what server is used).

The Magic requester(s) exposes this information to the Magic application which receives the request as global parameters (global variables). Inside your Magic Internet application you can access the CGI environment- and Server variables then with the function GetParam(). The IP address of the client you e.g. would get with GetParam('REMOTE_ADDR').

Since you cannot distinguish within your Magic application if a particular internet program was invoked by the Magic CGI requester, the ISAPI requester or the Apache loadable module requester, the mechanism for accessing CGI environment and server variables is the same. You use GetParam() to access the information. There are however differences in which information these different gateways provide to your application. Within a program invoked by the ISAPI requester you e.g. are able to retrieve more information than if the same program had been invoked by the CGI requester. Besides the environment variables defined in the CGI specification, the ISAPI requester will also expose some server variables which are specific to IIS.

Preparing your Magic & Internet application to receive environemnet and server variables HttpVars

There's two environment variables with information about the remote request which you can always query with GetParam(): REMOTE_ADDR and REMOTE_HOST. To be able to receive any other environment variable, you need to modify the HttpVars entry in the requester .ini (mgreq.ini) first. HttpVars needs to contain a comma seperated list with names of those variables which you want the requester to expose to your Magic application. If you do not put the name of a environment variable in this list, you cannot query its value.

If you want f.i. to be able to query the values of variables HTTP_REFERER, QUERY_STRING, HTTP_COOKIE within your Magic program, you need to put following information in the [REQUESTER_ENV] section of your mgreq.ini:

Do not intersperse blanks in the string following the "HttpVars=". Your requester may not be able to read this.

• It seems that the internet requester(s) saw quite a few changes in v9.4 SP8 (http://ftp.magicsoftware.com/ver/docs/Downloads/v9product/v94_sp8_ReleaseNotes.pdf∞ ).
• The problem described above (errror (-103): "Application not supported by any Enterprise server") does not occur anymore. The behaviour changed with v9.4 SP8:
  • REMOTE_ADDR and REMOTE_HOST are no longer filled by default. If you want to query this variables you have to put it into your mgreq.ini HttpVars= string like in
  • "HttpVars = REMOTE_ADDR,REMOTE_HOST" (without the quotes). Note that the blanks on the left and right of the "=" sign are mandatory now; if you specify (as in previous versions) HttpVars=REMOTE_ADDR,REMOTE_HOST you'll experience problems.
• • The length restriction for the HttpVars string seems to be still in place. If the string gets too long, the requesters do not provide you with the values in the Magic environment.
  • Different from before 9.4 SP8 is that the broker error (-103) does not occur anymore. If thats however better than not providing the application with the required values ... is a question.

Examples and list of possible CGI environment / Sever-variables

Below you find output of a sample program which echoes CGI environment and Internet Server variables from within a Magic application to html. The Magic program itself I made part of the Form-based File Upload in HTML sample which is available for download. Sample output is generated with IIS6.0 on Windows XP SP2. Other webservers may have a bit different set of variables. The Magic version I tested with was 9.4 SP8. The required HttpVars= definition in mgreq.ini was as given in the sample above. You'll note that some of the values for variables are NOT filled when you run the sample program with the CGI requester, while they ARE filled when you run the same program with the ISAPI requester. This is a limitation of the Magic 9.4 CGI requester.

Output of a CGI / server variable "echo" program written in Magic and invoked with 9.4 ISAPI requester and CGI requster:

Variable	return value ISAPI requester (mgrqispi94.dll)	return value CGI requester (mgrqcgi94.exe)
ALL_HTTP	HTTP_ACCEPT:image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-quickviewplus, */* HTTP_ACCEPT_LANGUAGE:en-us,de;q=0.5 HTTP_CONNECTION:Keep-Alive HTTP_HOST:andreas HTTP_REFERER:https://andreas/Magic94Scripts/MGrqispi94.dll?AppName=FileUpload&PrgName=ICA200_01&ARGUMENTS=-AgBCnMKMkb4nc-yObt2df4jLJ9S7UDDWq5zIf2kVIy0x1gbihbH879A== HTTP_USER_AGENT:Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1) HTTP_COOKIE:CVLANG=GB; sess_id="gBCnMKMkb4nc-yObt2df4jLJ9S7UDDWq5zIf2kVIy0x1gbihbH879A==" HTTP_UA_CPU:x86 HTTP_ACCEPT_ENCODING:gzip, deflate HTTP_X_REWRITE_URL:/Magic94Scripts/MGrqispi94.dll?AppName=FileUpload&PrgName=ICA500_10&ARGUMENTS=-AA
ALL_RAW	Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-quickviewplus, */* Accept-Language: en-us,de;q=0.5 Connection: Keep-Alive Host: andreas Referer: https://andreas/Magic94Scripts/MGrqispi94.dll?AppName=FileUpload&PrgName=ICA200_01&ARGUMENTS=-AgBCnMKMkb4nc-yObt2df4jLJ9S7UDDWq5zIf2kVIy0x1gbihbH879A== User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1) Cookie: CVLANG=GB; sess_id="gBCnMKMkb4nc-yObt2df4jLJ9S7UDDWq5zIf2kVIy0x1gbihbH879A==" UA-CPU: x86 Accept-Encoding: gzip, deflate X-Rewrite-URL: /Magic94Scripts/MGrqispi94.dll?AppName=FileUpload&PrgName=ICA500_10&ARGUMENTS=-AA
APPL_MD_PATH
APPL_PHYSICAL_PATH
APP_POOL_ID
AUTH_PASSWORD
AUTH_TYPE
AUTH_USER
CACHE_URL
CERT_COOKIE	455a84e84b12be870d80109937f91d63	455a84e84b12be870d80109937f91d63
CERT_FLAGS	1	1
CERT_ISSUER	C=ZA, O=Thawte Consulting (Pty) Ltd., CN=Thawte Personal Freemail Issuing CA	C=ZA, O=Thawte Consulting (Pty) Ltd., CN=Thawte Personal Freemail Issuing CA
CERT_KEYSIZE	128
CERT_SECRETKEYSIZE	4096
CERT_SERIALNUMBER	7c-2c-76-fc-01-14-6f-3e-56-65-a2-c8-a5-35-90-ec	7c-2c-76-fc-01-14-6f-3e-56-65-a2-c8-a5-35-90-ec
CERT_SERVER_ISSUER	C=DE, S=BAVARIA, L=MUNICH, O=ANDREAS SEDLMEIER CONSULTING, OU=IT, CN=ANDREAS' TEST CA, E=sedlmeier@hotmail.com
CERT_SERVER_SUBJECT	C=DE, S=BAVARIA, L=MUNICH, O=Andreas Sedlmeier Consulting Services, OU=IT, CN=andreas
CERT_SUBJECT	CN=Thawte Freemail Member, E=sedlmeier@hotmail.com
CONTENT_LENGTH
CONTENT_TYPE
GATEWAY_INTERFACE
HTTPS	on	on
HTTPS_KEYSIZE	128	128
HTTPS_SECRETKEYSIZE	4096	4096
HTTPS_SERVER_ISSUER	C=DE, S=BAVARIA, L=MUNICH, O=ANDREAS SEDLMEIER CONSULTING, OU=IT, CN=ANDREAS' TEST CA, E=sedlmeier@hotmail.com
HTTPS_SERVER_SUBJECT	C=DE, S=BAVARIA, L=MUNICH, O=Andreas Sedlmeier Consulting Services, OU=IT, CN=andreas
HTTP_ACCEPT	image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-quickviewplus, */*	image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-quickviewplus, */*
HTTP_ACCEPT_ENCODING	gzip, deflate	gzip, deflate
HTTP_ACCEPT_LANGUAGE	en-us,de;q=0.5	en-us,de;q=0.5
HTTP_CONNECTION	Keep-Alive
HTTP_COOKIE	CVLANG=GB; sess_id="gBCnMKMkb4nc-yObt2df4jLJ9S7UDDWq5zIf2kVIy0x1gbihbH879A=="
HTTP_HOST	andreas	andreas
HTTP_REFERER	https://andreas/Magic94Scripts/MGrqispi94.dll?AppName=FileUpload&PrgName=ICA200_01&ARGUMENTS=-AgBCnMKMkb4nc-yObt2df4jLJ9S7UDDWq5zIf2kVIy0x1gbihbH879A==
HTTP_USER_AGENT	Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727;InfoPath.1)
HTTP_VERSION	HTTP/1.1
INSTANCE_ID	1	1
INSTANCE_META_PATH	/LM/W3SVC/1
LOCAL_ADDR	172.23.107.107
LOGON_USER
PATH_INFO
PATH_TRANSLATED	C:\web.dev\www\htdocs	C:\web.dev\www\htdocs
QUERY_STRING	AppName=FileUpload&PrgName=ICA500_10&ARGUMENTS=-AA	AppName=FileUpload&PrgName=ICA500_10&ARGUMENTS=-AA
REMOTE_ADDR	172.23.107.107
REMOTE_HOST	172.23.107.107
REMOTE_PORT	1380
REMOTE_USER
REQUEST_METHOD
SCRIPT_NAME
SCRIPT_TRANSLATED
SERVER_NAME
SERVER_PORT
SERVER_PORT_SECURE
SERVER_PROTOCOL
SERVER_SOFTWARE
SSI_EXEC_DISABLED
UNENCODED_URL
UNMAPPED_REMOTE_USER
URL

See also

- The Common Gateway Interface∞
- RFC 1867 - Form-based File Upload in HTML - with eDeveloper (which contains the sample program to generate above sample output)


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