WIKIFS(4) WIKIFS(4)
NAME
wikifs, wikipost - wiki file system
SYNOPSIS
wikifs [ -DM ] [ -a announce ]... [ -m mtpt ] [ -p perm ] [
-s service ] dir
ip/httpd/wikipost [-b inbuf] [-d domain] [-r remoteip] [-w
webroot] [-N netdir] method version uri [search]
DESCRIPTION
A wiki is a web server that facilitates easy editing of the
pages it contains. Wikifs presents a wiki in two forms: as
web pages to be served via httpd(8) and as text files to be
viewed via the acme(1) wiki client (see /acme/wiki/guide).
Wikifs presents a file system interface to the wiki data
stored in dir. By default, wikifs mounts itself at
/mnt/wiki; the -m flag specifies a different mount point,
and the -M flag causes wikifs not to mount at all. Wikifs
also announces 9P network services on the addresses given as
arguments to -a options. If the -s option is given, wikifs
will post a service file descriptor in /srv/service with
permission perm (default 600). The -D flag causes a tran-
script of the 9P conversation to be written to standard
error.
The wiki holds both the current pages and also all versions
of all pages that have ever existed. All pages have time
stamps associated with them. When a user wants to edit a
page, he reads the current page from the wiki, noting the
time stamp on the page. When a user writes changes to a
page, he includes the time stamp of the page he started
with. If the page has been updated by someone else while he
was editing, the write will fail. This is called a ``con-
flicting write.'' The submission is still saved in the his-
tory, so that the user can compare the page he submitted
with the changes that were made while he was editing.
Each version of each page is described by a text file con-
taining one or more metadata lines followed by the page con-
tents. The metadata lines begin with a capital letter spec-
ifying the type of data. Currently the metadata types are:
D The date this page was written, in decimal seconds
since the epoch.
A The author of this version of the page. Typically the
rest of the line takes the form name ip-address.
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X This page's contents were submitted but rejected due to
a conflicting write.
After the metadata comes the actual page contents; each line
of page contents is prefixed with a # character.
The directory dir/d contains all the wiki data. Typically
it is world-writable so that wikifs can run as none. Each
page on the wiki has a unique sequence number n; for each
page, the d directory contains three files n, n.hist, and
L.n. The file n holds the current version of the page: the
first line of n is the page title, followed by page metadata
and contents as described above. The append-only file
n.hist holds the history of the page. The first line of
n.hist is the title of the page. The rest of the file is
the metadata and contents of every version of the page that
has been submitted to the wiki. L.n is a lock file for the
page: it must be held while reading or writing n and n.hist.
The lock files allow multiple instances of wikifs to coexist
peacefully. Finally, the map file (with associated lock
L.map) provides a mapping from sequence numbers to page
titles. Each map line is a decimal n, a single space, and
then the title. Since titles are presented as names by
wikifs, they cannot contain slashes.
Wikifs presents a three-level file system. The top level
contains per-page directories named by the page titles with
spaces turned into underscores. Each page also has a number
associated with it (see the discussion of the wiki data
files below). The number corresponding to a page may also
be used to access it, although directory listings will
always present the title. The new file is used to add new
or revised pages to the wiki: writes to the file should be
in the usual textual format: a title line, metadata lines,
and page contents. Once all the contents have been written,
a final zero-length message should be written to mark the
end of the page. This last write will return an error if a
conflicting write has occurred. After writing the file, the
client may read from new to obtain the canonical title for
the page, as presented by the file system.
The page directories contain subdirectories representing the
history of the page, named by the decimal time stamp corre-
sponding to each version. In addition to these history
directories, the page directories contain the following
files:
current
The current raw data file for the page.
diff.html
A web page listing the contents of every version of the
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page that has ever appeared on the wiki. The text is
grey by default: differences between versions appear in
black.
edit.html
A web form for editing the current version of the page.
history.html
A web page listing the time stamps of the historical
versions of the page. Each time stamp links to a page
showing just that version.
history.txt
A textual formatting of the history. Each time stamp
is prefixed with the name of the directory correspond-
ing to that version.
index.html
An HTML formatting of the current version of the page.
index.txt
A textual formatting of the current version of the
page.
werror.html
An HTML error page to be returned by wikipost on con-
flicting writes.
The HTML files are generated from the templates with the
same names in dir, except that index.html and index.txt are
generated from the templates page.html and page.txt.
The history directories are similar to the page directories
but only contain current, index.html, and index.txt. This
index.html and index.txt are generated from the templates
oldpage.html and oldpage.txt.
The httpd(8) helper program wikipost is used to process
editing requests posted to the web server by users. It
expects the posted form to contain these (usually hidden)
fields: TITLE, the title of the page; VERSION, the time
stamp of the page that is being edited; service, the service
name associated with this wiki (wikipost looks for
/srv/wiki.service); and base, the base for wiki URLs in the
response.
After mounting the wiki, wikipost writes a page update
request to /mnt/wiki/new and then returns the contents of
one HTML file in /mnt/wiki/title. If the write succeeds,
wikipost returns index.html. if the write fails due to a
conflicting write, wikipost returns werror.html.
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EXAMPLE
The Plan 9 wiki at Bell Labs is started by running:
wikifs -p 666 -s wiki.plan9 -a tcp!*!wiki /sys/lib/wiki
The wiki is mounted for httpd(8) by an entry in
/lib/namespace.httpd:
# wiki
mount -b #s/wiki.plan9 /usr/web/wiki/plan9
Notice that the wiki service was explicitly posted with mode
666 so that httpd (running as none) would be able to mount
it.
In the Plan 9 distribution, the directory /sys/lib/wiki con-
tains sample files similar to those used to start the cur-
rent Plan 9 wiki.
SOURCE
/sys/src/cmd/wikifs
/sys/src/cmd/ip/httpd/wikipost.c
SEE ALSO
The original wiki, http://c2.com/cgi/wiki?WikiWikiWeb
/acme/wiki/guide
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