Character encoding

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Character encoding  edit   (Category  edit) Category:Character encoding

Category Character encoding not found


http://www.joelonsoftware.com/articles/Unicode.html The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) - Joel on Software

Contents

[edit] Unicode

http://unicode.org/faq/utf_bom.html#1


[edit] Converting

To convert a file from Latin1 (iso-8859-1) to UTF-8:

iconv -f iso-8859-1 -t utf-8 file.html


[edit] Browsers

http://www.joelonsoftware.com/articles/Unicode.html. Retrieved on 2007-05-11 11:18.

For a web page, the original idea was that the web server would return a similar Content-Type http header along with the web page itself -- not in the HTML itself, but as one of the response headers that are sent before the HTML page.

This causes problems. Suppose you have a big web server with lots of sites and hundreds of pages contributed by lots of people in lots of different languages and all using whatever encoding their copy of Microsoft FrontPage saw fit to generate. The web server itself wouldn't really know what encoding each file was written in, so it couldn't send the Content-Type header.

It would be convenient if you could put the Content-Type of the HTML file right in the HTML file itself, using some kind of special tag. Of course this drove purists crazy... how can you read the HTML file until you know what encoding it's in?! Luckily, almost every encoding in common use does the same thing with characters between 32 and 127, so you can always get this far on the HTML page without starting to use funny letters:

    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

But that meta tag really has to be the very first thing in the <head> section because as soon as the web browser sees this tag it's going to stop parsing the page and start over after reinterpreting the whole page using the encoding you specified.


[edit] Apache

http://httpd.apache.org/docs/2.0/mod/core.html#adddefaultcharset. Retrieved on 2007-05-11 11:18.

AddDefaultCharset Directive

This directive specifies a default value for the media type charset parameter (the name of a character encoding) to be added to a response if and only if the response's content-type is either text/plain or text/html. This should override any charset specified in the body of the response via a META element, though the exact behavior is often dependent on the user's client configuration. A setting of AddDefaultCharset Off disables this functionality. AddDefaultCharset On enables a default charset of iso-8859-1. Any other value is assumed to be the charset to be used, which should be one of the IANA registered charset values for use in MIME media types. For example:

AddDefaultCharset utf-8

AddDefaultCharset should only be used when all of the text resources to which it applies are known to be in that character encoding and it is too inconvenient to label their charset individually. One such example is to add the charset parameter to resources containing generated content, such as legacy CGI scripts, that might be vulnerable to cross-site scripting attacks due to user-provided data being included in the output. Note, however, that a better solution is to just fix (or delete) those scripts, since setting a default charset does not protect users that have enabled the "auto-detect character encoding" feature on their browser.

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