WEBFS(4) WEBFS(4)
NAME
webfs - world wide web file system
SYNOPSIS
webfs [ -Dd ] [ -A useragent ] [ -T timeout ] [ -m mtpt ] [
-s service ]
DESCRIPTION
Webfs presents a file system interface to the parsing and
retrieving of URLs. Webfs mounts itself at mtpt (default
/mnt/web), and, if service is specified, will post a service
file descriptor in /srv/service. The -d flag enables gen-
eral debug printing to standard error while the -D flag
enables 9P debug prints.
If the environment variable httpproxy is set, all HTTP
request initiated by webfs will be made through that proxy
url.
Webfs presents a three-level file system suggestive of the
network protocol hierarchies ip(3) and ether(3).
The top level contains the two files: ctl, and clone.
The top level ctl file is used to maintain parameters global
to the instance of webfs. Reading the ctl file yields the
current values of the parameters. Writing strings of the
form ``attr value'' sets a particular attribute.
The following global parameters can be set:
useragent
Sets the HTTP user agent string.
timeout
Sets the request timeout in milliseconds.
flushauth url
Flushes any associated authentication information for
resources under url or all resources if no url was
given.
preauth url realm
Preauthenticates all resources under url with the given
realm using HTTP Basic authentication. This will cause
webfs to preemptively send the resulting authorization
information not waiting for the server to respond with
an HTTP 401 Unauthorized status.
The top-level directory also contains numbered directories
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WEBFS(4) WEBFS(4)
corresponding to connections, which may be used to fetch a
single URL. To allocate a connection, open the clone file
and read a number n from it. After opening, the clone file
is equivalent to the file n/ctl. A connection is assumed
closed once all files in its directory have been closed, at
which point its index may be reused.
Each connection has a URL attribute url associated with it.
This URL may be an absolute URL such as
http://www.lucent.com/index.html or a relative URL such as
../index.html. The baseurl attribute sets the URL against
which relative URLs are interpreted. Once the URL has been
set by writing to the ctl file of the connection, its pieces
can be retrieved via individual files in the parsed direc-
tory:
parsed/url
http://pete:secret@www.example.com:8000/cgi/search?q=kittens#results
parsed/scheme
http
parsed/user
pete
parsed/pass
secret
parsed/host
www.example.com
parsed/port
8000
parsed/path
/cgi/search
parsed/query
q=kittens
parsed/fragment
results
If there is associated data to be posted with the request,
it can be written to postbody. Opening postbody or body
initiates the request. If the request fails, then opening
the body or writing to postbody file will fail and return a
error string.
When the body file has been opened, response headers appear
as files in the connection directory. For example reading
the contenttype file yields the MIME content type of the
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WEBFS(4) WEBFS(4)
body data. If the request was redirected, the URL repre-
sented by the parsed directory will change to the final des-
tination.
The resulting data may be read from body as it arrives.
The following is a list of attributes that can be set for a
connection prior to initiating the request:
url,baseurl
See above.
useragent
Sets a custom useragent string to be used with the
request.
contenttype
Sets the MIME content type of the postbody.
request
Usually, the HTTP method used is POST when postbody
file is opened first or GET otherwise. This can be
overridden with the request attribute to send arbitrary
HTTP requests.
headers
Adds arbitrary HTTP headers to be sent with the
request.
EXAMPLE
/rc/bin/hget is a simple client.
SOURCE
/sys/src/cmd/webfs
SEE ALSO
webcookies(4), hget(1)
DIAGNOSTICS
For cookies to work, webcookies(4), should be running and
mounted on /mnt/webcookies otherwise cookies will be
ignored.
HISTORY
Webfs first appeared in Plan 9 from Bell Labs. It was
rewritten from scratch for 9front (January, 2012).
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