Execution Handler
目次- 1.0.0 Location
- 2.0.0 Description
- 3.0.0 Configuration
- 4.0.0 Comparison with Apache CGI
- 5.0.0 Error handling in CGI program
- 6.0.0 Relation to URI
- 7.0.0 Name space of CGI
- 8.0.0 Environment variable of CGI
- 9.0.0 Handling of POST data
- 10.0.0 CGI timeout
Location
$web/etc/handler
Description
Execution handler is a program that processes files of specific path pattern. User can define relations between path pattern and the handler. This mechanism is used to define the form of CGI file, SSI (Server Side Include) and auto-indexing service for specific directories.Configuration
Relations between path patterns and the handler is defined in$web/etc/handler
. The following is the content of my configuration (http://plan9.aichi-u.ac.jp
).# path mimetype unused execpath arg ... /netlib/*/index.html text/html 0 /bin/ftp2html *.http - 0 $target *.html text/html 1 $target *.dx_html text/html 0 /bin/dx $targetThe first field is a path pattern and the 4th field is the path to handler. The second field indicates how to do that, and the third fields is currently unused.
Comparison of path pattern and requested path is performed from the top of line. Comparison is stopped if pattern is matched to the requested path.
Arguments of the program may continue after 4th field.
In path pattern, directory separator "/
"' is not special. ( Therefore this pattern matching is not same as that of shell. ) There is one exception: we have a rule that pattern "/*/
" matches "/
". Therefore the pattern
/netlib/*/index.htmlmatches to
/netlib/index.html
as well as /netlib/cmd/backup/index.html
for example.Second field denotes "
ContentType
" of HTTP header. If the field is "-
", the handler must send all HTTP headers.Third field is not used. This field was
ramfs
but obsoleted because ramfs
is always serviced to CGI program in current version.
The 4th field is the path to handler. Handler must be a executable.
$target
in or after 4th field denotes absolute path to the requested document. Note that $target
in 4th field means the requested path is an executable program.
Clients can request to Pegasus adding arguments to CGI . These arguments are automatically added without description in handler
.
/bin/ftp2html
in this example is a program that is used in
http://plan9.aichi-u.ac.jp/netlib/to handle my FTP directories. Other server such as Apache has an option to show directory index if index.html is absent.
ftp2html
also does this action but does much more: if README file is present then the content is shown, and if INDEX file is present then the content is shown with appropriate action tag to the index label./bin/dx
is a tool that is designed by the author to be used for SSI.
Comparison with Apache CGI
Iftext/html
is specified for mimetype , the format of CGI is:<html> ... </html>That is, don't start with "Content-Type" as Apache do:
Content-Type: text/html <html> ... </html>
Error handling in CGI program
Now Pegasus can easily pass response code to the client. Therefore you might not need "-
" for mimetype
.In case that
text/html
is specified for mimetype
Pegasus automatically send HTML headers to the client. Then response header becomes following rule:- "
200 OK
" is sent if exit status is not given.
connection will be kept
- if response header is given as exit status, then Pegasus passes it to client.
connection will be kept, if the code number is 100 to 299. otherwise connection will be closed.
- if exit status is not a response header of HTTP, Pegasus will send "
200 OK
" and close the connection. This specification is for compatibility to old version.
keep
" or "close
" after "#
"exit '403 Forbidden # keep'
Both stdout
and stderr
are passed to client.
Relation to URI
Params in HTTP/1.0 及び HTTP/1.1 is applied to Pegasus. According to RFC specification the format is:path;params?query params = param[;params]Some of traditional web server neglect
params
and passe query
to CGI as the argument. Pegasus disapproves this traditional manner and accepts param
as argument parts that should be passed to CGI. On the other hand, Pegasus does not participate in interpritating query
and passes it to CGI as environment variable without translation.
Name space of CGI
The name space for CGI program can be modified using/etc/namespace_80where
80
is the port number.
Environment variable of CGI
Pegasus has many environment variables. However most of them are only experimental. Solid variables are shown in the following:GATEWAY_INTERFACE SERVER_NAME SERVER_PORT SERVER_SOFTWARE SERVER_PROTOCOL REQUEST_METHOD REMOTE_ADDR QUERY_STRING HTTP_HEADER HTTP_HOST HTTP_REFERER HTTP_USER_AGENT REQUEST_PATH # requested path (see Note) REQUEST_URI # requested path (see Note) home # /doc query # same as QUERY_STRING target # requested path in service space name # basename of target cputype # 386 objtype # 386 date # date such as "{Mon, 04 Mar 2002 07:32:40 GMT}"
REQUEST_URI
might end with "/
" if it is a directory. On the other hand REQUEST_PATH
is a file that is effectively requested. target
is expressed in the notation of rc
.target = /doc$REQUEST_PATH
Other environment variables might be discarded or renamed in future.
Handling of POST data
If POST'ed data is once received by the server from the client,Content-Length
is checked by the server in receiving the data. Then server passes the data to CGI using stdin.
CGI timeout
Timeout is defined to prevent buggy programs waiting data so long time. The value can be specified in httpd option or/sys/lib/httpd.conf
. The default is 5 second. I think the value is enough because the data is already held by the server.