SDF Gopher Tutorial
[From http://sdf.org/?tutorials/gopher]
Contents
1. What is Gopher
2. Creating your gopherspace
3. Gopher log
4. Dynamic content (moles)
What is Gopher?
From: http://en.wikipedia.org/wiki/Gopher_(protocol)
The Gopher protocol is a TCP/IP Application layer protocol
designed for distributing, searching, and retrieving documents
over the Internet [...]. The protocol offers some features not
natively supported by the Web and imposes a much stronger
hierarchy on information stored on it.
You can find more info here:
* FAQ > GOPHER
* http://www.scn.org/~bkarger/gopher-manifesto
* http://gopher.floodgap.com/overbite/relevance.html
Creating your Gopherspace
You can use the command "mkgopher" (after you run it, type
"setup" in the line "MKGOPHER> "; you can type "help" for more
details) to create a directory in your $HOME called "gopher"
(This directory is a link to /ftp/pub/users/$USER/ ). On it, you
can put all the files you want to be available in your
Gopherspace.
You can use mkgopher to publish documents, create directories,
etc. You can also manage your Gopherspace manually. If you decide
to do so, remember that the server will not display your content
if it is not already visible to everyone. That is, files need to
world-readable (chmod o+r $HOME/gopher/yourfile), directories
need also to be world executable (chmod o+rx
$HOME/gopher/yourdir), etc. The gopher server (Gophernicus) will
serve executable files under /cgi-bin and also gophermaps which
have executable permission as gopher CGIs or "moles" (see
below). In the case of gophermaps, this is likely to result in
errors, so make sure your gophermaps do not have execute
permission (chmod -x $HOME/gopher/yourdir/gophermap).
The usual 'mkgopher -p' command has not yet been updated to
reflect Gophernicus' permissions requirements. So you may need to
reset your permissions for all files and directories in your
gopher directory as noted above. The following two commands will
revert all files to world-readable but non-executable, and all
directories to world-readable but executable.
find ~/gopher -type f -print0 | xargs -0 chmod 644
find ~/gopher -type d -print0 | xargs -0 chmod 755
You may need to manually add execute permissions to any dynamic
gophermaps or files under /cgi-bin after runnig these two
commands.
Gophermap
Note: You can view the sample gophermap that comes with
Gophernicus here: README.Gophermap
Say that you have "file1.txt", "file2.pdf", "file3.rtf" and "dir"
in your Gopherspace ("dir" is a directory). That is,
$ ls -lF
drwxr-x--- 2 $USER nobody 512 Dec 2 10:15 dir/
-rw-r----- 1 $USER nobody 6 Dec 2 10:14 file1.txt
-rw-r----- 1 $USER nobody 6 Dec 2 10:14 file2.pdf
-rw-r----- 1 $USER nobody 6 Dec 2 10:14 file3.rtf
When you visit it, if there is no file named "gophermap" (yes,
this file has no extension) you'll see a list of the files and
the directory, like this:
Gopher Menu
(DIR) dir
(FILE) file1.txt
(FILE) file2.pdf
(FILE) file3.rtf
If there is a gophermap file, the server will parse it and will
present the content as you specified in gophermap.
The gophermap syntax is:
XSome text here<TAB>/path/to/content<TAB>example.org<TAB>N
where the first character ("X" in the example) is an "itemtype"
(more below), "Some text here" is the text that you want to be
displayed, <TAB> is a tab character, "/path/to/content" is the
location of the content, "example.org" is the server where the
content is located and the last character ("N" in the example) is
the server port (usually it's 70). Content after the second <TAB>
is optional if you are linking to content in your Gopherspace.
The "itemtype" is one of these characters:
Itemtype Content
0 Text file
1 Directory
2 CSO name server
3 Error
4 Mac HQX filer
5 PC binary
6 UNIX uuencoded file
7 Search server
8 Telnet Session
9 Binary File
c Calendar (not in 2.06)
e Event (not in 2.06)
g GIF image
h HTML, Hypertext Markup Language
i "inline" text type
s Sound
I Image (other than GIF)
M MIME multipart/mixed message
T TN3270 Session/
Gophermap example
OK, let's say that you want to display a welcome message, a
description for "file1.txt", "file2.pdf"and "dir", a link to an
external server, a link to an http URL. Your gophermap should be
like this:
Welcome to my Gopherspace!
0My text file file1.txt
9My pdf file file2.pdf
1My dir dir
0Why is Gopher Still Relevant? /gopher/relevance.txt gopher.floodgap.com 70
hAn http link URL:http://sdf.org/
Remember the gophermap syntax? Then be careful about tab
characters. In the example above, there are some <TAB>s. For
instance, the third line is
0My text file<TAB>file1.txt
while the seventh is
0Why is Gopher Still Relevant?<TAB>/gopher/relevance.txt<TAB>gopher.floodgap.com <TAB>70
How come the pdf file has an itemtype 9? Well, not every kind of
file has its own itemtype, so you can use one that makes more
sense.
Even if you don't need a blank line as the second line of your
document, you can find this useful as there is a known Lynx bug
that makes it display the second line together with the first
(you can find a patch for this here:
gopher://sdf.org/0/users/bulibuta/openbsd/patches/lynx-gopher-
newline.patch).
This is (more or less) the output you'll see if you use a
gophermap like the one in the example above:
Gopher Menu
Welcome to my Gopherspace!
(FILE) My text file
(BIN) My pdf file
(DIR) My dir
(FILE) Why is Gopher Still Relevant?
(HTML) An http link
Gopher log
A gopher log ("glog" or "phlog") is similar to a blog, but on
gopherspace. You can create your phlog and add it to the
phlogosphere.
Maintaining a glog consists basically (but not necessarily) in
creating an entry (in your log directory) and modifying your
phlog gophermap so that the new entry is displayed with its
creation date. There's a script that you can run on SDF called
"mkgopherentry" (located in /sys/sdf/bin/mkgopherentry) that will
allow you to do exactly that. It will also extract the first
paragraph from the entry and will add it on the gophermap with a
"Continued..." link that will point to the full post. Creating an
entry is as simple as: mkgopherentry title textfile
where the 2 arguments are self-explaining.
Say that you have two entries in your diary. If you use
"mkgopherentry", they will appear like:
--This is my second post!--
Tuesday, December 01th, 2009
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Cras eros turpis, tristique semper aliquet sit amet,
hendrerit vel enim. Integer pulvinar leo in dolor posuere
blandit.
Continued...
--First post--
Monday, November 30th, 2009
First entry in my gopher log at SDF.
Continued...
Other glog/phlog software
There are some software authored by SDF members that you could
find useful if you want to maintain a gopher log.
germ
gopher://sdf.org/1/users/wt/soft/my/germ/
slerm
gopher://sdf.org/0/users/slugmax/about-slerm.txt
gopher://sdf.org/9/users/slugmax/code/slerm-1.8.tgz
http://slugmax.tx0.org/slerm-1.8.tgz
glog
gopher://sdf.org/0/users/yargo/scripts/glog.sh
mkphlog
gopher://sdf.org/1/users/octotep/scripts/mkphlog/
phlogit
gopher://sdf.org/0/users/slugmax/code/phlogit.txt
tirph
gopher://sdf.org/1/users/papa/tirph
ugo
gopher://sdf.org/1/users/chr/scripts/ugo/
You can find more resources in the "Glogging/Phlogging" section
at gopher://sdf.org/1/users/wt/soft/gopher.
Dynamic content (gopher CGIs or moles)
The server used by SDF (Gophernicus) is able to serve
"moles". Moles are executable files under /cgi-bin that are
processed by the server as CGIs. This means that you can write a
script, that the server will execute and it will present the data
that your mole dumps to standard output. With moles you don't
have to declare a content type header. Moles get arguments from
the address used to access the document and can be accessed with
whatever itemtype makes sense for the kind of output the mole
generates.
You can code moles with the language(s) you are comfortable and
can use on SDF. Below we will see some examples using shell
scripts.
Mole examples
Remember that your moles need to be executable (and readable) by
everyone, and under /cgi-bin. So you will have to do: chmod 755
YOURSCRIPT.cgi
fortune.cgi
The following example will generate a random fortune:
#!/bin/sh
/usr/pkg/games/fortune
Easy enough, isn't it? As it is raw text, you can access it using am
itemtype = 0, that is:
gopher://sdf.org/0/users/YOUR-USERNAME/cgi-bin/fortune.cgi
Did you notice that "fortune" was called with a full path? OK,
that's because the server's path is
"PATH=/sbin:/bin:/usr/sbin:/usr/bin". That means that if you call
a program without a path, the server will search in "/sbin",
"/bin", "/usr/sbin" and "/usr/bin". There's no "/usr/pkg/games",
or other path in the server's $PATH (eventually, you can add a
path of your choice with, e.g., PATH=$PATH:/usr/pkg/games).
ls.cgi
The following example will generate a list of files on a
specified directory. It will be possible to sort the content
alphabetically or by modification time, based on how you access
the script.
#!/bin/sh
directory=/ftp/pub/users/YOUR-USERNAME
rel_dir=/users/YOUR-USERNAME
server=sdf.org
port=70
# The internal field separator is set to be a newline
IFS='
'
if [ -n "$1" -a "$1" = 'date' ] ; then
ls_arg=t
fi
for i in $(ls -l${ls_arg} $directory) ; do
content=$(echo "$i" | awk '{ print $9}')
date=$(echo "$i" | awk '{ print $6,$7,$8}')
if [ -z "$content" ] ; then
continue
fi
if [ -d $directory/$i ] ; then
itemtype=1
else
itemtype=0
fi
echo "$itemtype$content ($date) $rel_dir $server $port"
done
Note that the "echo..." line is
echo "$itemtype$content ($date)<TAB>$rel_dir<TAB>$server<TAB>$port"
If you go to
gopher://sdf.org/1/users/YOUR-USERNAME/cgi-bin/ls.cgi,
you will see a list of your files sorted alphabetically. If you
access your mole as
gopher://sdf.org/1/users/YOUR-USERNAME/cgi-bin/ls.cgi?date,
then you'll see your files/directories sorted by modification
time.
figlet.cgi
You can add some interactivity by using the itemtype 7. This
itemtype is intended to make it possible to type some characters
in a search field in your browser. However, you can use it to
make it possible to pass arguments to your scripts. The following
example will use some text you digit in the search field and will
pass it through the program "figlet".
#!/bin/sh
IFS='
'
for line in $(/usr/pkg/bin/figlet "$@") ; do
echo "i$line" # This is itemtype=i + text
done
When you access the script via
gopher://sdf.org/7/users/YOUR-USERNAME/cgi-bin/figlet.cgi
, your browser will ask you to input some text (the way it ask
depends on the browser), then it will show your text as figlet
transforms it.
The "i" in the "echo..." line is important here. Indeed, the
document is been accessed with an itemtype "7" (but the same
applies for itemtype "1"), so the document should be structured
similarly to gophermaps. It's not a gophermap, though. That's why
you need to explicitily state the line should be displayed as
simple (or "inline") text.
Caveat
Besides what was said in the last paragraph of the "figlet.cgi"
example, there's also another thing to stress. In that example
(as with anything that will be served as a virtual directory or
with an itemtype 1 or 7), content won't be displayed if you
access your script via floodgap proxy (and maybe others). In this
case you will need to "format" the output of your script. Luckily
this is very easy. For instance, in the figlet.cgi example you
will need to modify the "echo ..." line this way: echo
"i$i<TAB><TAB>error.host<TAB>1" where <TAB> is a tab character
(you should already know this!)C and "error.host" and "1" are,
respectively, a fake server and port number (you could also have
written "fake" instead of "error.host" and "300" instead of "1").
$Id: gopher.html,v 1.19 2017/05/08 17:21:40 slugmax Exp $