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Understanding
the web site file system
index.php
and why you should use it:
This
again is where a number of newer webmasters
become stumped. They upload all of their files
and directories, and then want to access them
with their browser, but forgetting to create
their welcoming page as index.php, so here's
what happens: They access their site as
http://www.mydomain.com/ or using the associated
IP number, for example, http://test.php/, and
what they see is their entire file directory
structure! Yikes!… It looks just like exploring
the C drive on your computer! You don't want
visitors seeing that, do you?
When you
access your site by calling it as http://www.mydomain.com or
the assigned IP (for example), http://
216.74.122.26/, the
web server looks for the "index.php" file as
the (default file) to be sent to visitors, and
thus this is why http://www.mydomain.com/ by
itself will automatically display the home or
welcoming page. It's because the server
automatically looks for index.php whenever a
domain or directory is called without a filename
appended to it such as this,
http://www.mydomain.com/file.php
If it
can't find index.php, it will simply list "your
entire web directory" to everyone that access's
it, which is a MAJOR security risk! ALWAYS, use
an "index.php" file in any directory you
create, including your "root" web directory. In
general, it's always a good idea to use
"index.php" as your main page in "all
sub-directories" of your account. Forgetting to
place an index.php in your root web, or any
subdirectory of your web for that matter will
effectively leave all of its contents viewable
to the world.
Understanding
case sensitivity:
Another
small detail, which can throw many newer users
into a tailspin. Unlike your local PC, the Unix
file system is very particular about "uppercase"
and "lowercase" file names. Therefore, if you
were to install a script, (let's say the
wwwboard discussion forum) for example), the
name of this script would be wwwboard.pl.
If you name a file picture file called me.jpg,
then this is what you must call it as.
Naming it me.JPG for example, (observe the
uppercase) tells a Unix web server to treat it
as a totally different file name.
Unix
file servers are exceptionally fussy on this
issue, so make sure you pay close attention to
"case' when uploading files, or installing and
configuring cgi based scripts. The same rule
applies for all files including your .php
pages. Again, the server treats .php and .php
as two entirely different files. Want to keep in
simple? Try to stick with lowercase letters in
all file names and
extensions.
Uploading
your files in the correct mode (ASCII or
Binary)?
Uploading
in the wrong format for images or binaries will
result in a strange mess appearing in place of
the file. For CGI scripts, this mistake
has to be the most common cause of that annoying
error known as the (Server 500 Error - Malformed
Headers), or something to that lovely extent.
While this can be the result of many various
programming errors, the most popular amongst new
users are uploading their scripts in the "WRONG"
format. Your cgi scripts "MUST" always be
uploaded in ASCII mode. Alternatively, if you
upload an image or .exe file, it must be done in
"BINARY" mode.
The
difference between ASCII and
BINARY?
In
short, html or text based files are supposed to
be transferred in ASCII mode. Uploading them in
Binary mode will append ^M's to the end of every
line. In most cases, this is OK, with html files
because your browser will ignore them. BUT, with
other text files such as cgi scripts, uploading
them in binary will damage them, thus causing a
(server 500 error). This is because binary mode
has added ^M's to the end of every line, which
are not supposed to be in the program. This of
course, is what causes the additional message of
(Malformed Headers), which often displays at the
bottom of the "Server 500" message when a CGI
script has crashed.
Once again, BINARY
mode is used for transferring executable
programs, compressed files and all image/picture
files. If you try to upload an image in ASCII
mode, you observer a strange mess appearing on
the page where the image is suppose to appear.
ASCII mode in this case, has corrupted the
binary coding in the jpeg or gif image. If this
happens, just re-upload it in the Binary
format
Setting
your FTP client to automatically detect ASCII
and Binary file transfers:
Most
FTP programs have "AUTO" mode, which will tell
the FTP client to automatically detect the file
type you're transferring and will select the
appropriate mode. By default, most FTP programs
will attempt to transfer everything in binary
mode, but when "Automatic" is selected, the FTP
client will check a list of known ASCII
extensions, (for example, .pl, .cgi, .txt). If
it detects one of these extensions, it
automatically switches to ASCII mode.
By
Default, most of the well-known files to be
uploaded in ASCII are already entered, however
you can manually add additional extensions that
you would like to transfer in ASCII mode by
selecting the feature called "Extensions." Here,
you can any additional extensions that will
cause the FTP client to toggle to ASCII mode
automatically upon detecting an extension
entered in its list. Remember, you must set your
transfer mode to "Automatic" for this to
work.
File
types and what they
represent:
Various
file types can effect both the behavior of your
files, as well as how the server treats them.
While there are numerous file extensions, which
represent a host of various file types, we'll
stick to the basic ones in this quick
overview:
The
.php file:
This
is one is the most commonly used and the most
one of you are already familiar with. Html
stands for (hypertext Markup Language).
Essentially, it tells the server, as well as the
clients browser to process and display the .php
coding in a way, which is meaningful to the end
user through a
browser.
The
.htm file:
Many
of you have probably noticed this newer
extension appearing in place of the traditional
.php one. In short, .htm is most often created,
and or generated from the Microsoft FrontPage
web editor. The two are essentially the same and
provide the same basic purpose. Unless you're
using FrontPage, you will probably use the .php
extension at the end of your web
pages.
The
.gif and .jpg file:
Most
commonly used because of its good compression in
web page images. Generally, .gif files are the
fastest loading, as they remove a lot of
information, which is not required to maintain
image integrity, but to a point however. .jpg
will allow more flexibility in compression and
quality settings, however can also result in
larger files.
The
.CGI and the .pl file:
.cgi
and .pl are most often used for perl scripts.
Perl scripts are small text based programs,
which are executed on the server end, and will
perform a host of interactive functions for a
web site. In short, when a .pl or .cgi file is
called, it tells the server to process it using
the "Perl Interpreter." The Perl Interpreter
understands the programming within the script,
and will perform the set of sub routines, which
will yield your desired effect. This desired
effect could be anything from a simple web page
counter, to more complex programs such as
discussion forums, e-commerce platforms, to
online auctions. In many cases, you can download
these "ready to go" scripts for free, and in
others you may have to purchase them.
FrontPage
and FTP:
If
you're planning on using Microsoft FrontPage to
manage your web site, there are a couple of
issues things you may want to keep in
mind:
There are two worlds. The General
Unix hosting world, and the Microsoft world.
While this is not necessarily a bad thing,
Microsoft had indeed decided to play by its own
rules. As a result, FrontPage does
not always conform to the rules of Unix, so you
should be extremely careful when accessing a
FrontPage web via FTP. It's easy to damage
the FrontPage web, as well as it's associated
server extensions, and if it happens, you may
loose the ability to administrate it from your
FrontPage Explorer. To avoid problems like
this:
- Do
not alter, or delete files that are part of a
FrontPage web
- Do
delete, move, or alter directories ending in
_vtf. These are the FrontPage extensions
The
ultimate solution:
If
possible, try to create your FrontPage webs in
sub-directories of your root. For example,
http://www.yourdomain.com/home. This way, you
can safely FTP into your root account to perform
other tasks, while avoiding the FrontPage webs,
which are safely out of the way in their own
separate homes. Remember! DO NOT delete any
folders, which end in _vtf! This will kill your
FrontPage web, and we'll have to reinstall the
extensions for you. For additional
information on FrontPage, please see our
dedicated tutorial on it.
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