How do I conditionally handle undefined SSI variables using Apache?

Question

I want to include a header in a bunch of pages, like so:

header.html:

<html>
  <head>
    <title>My site</title>
  </head>

To enable a page-specific title, I'm trying to use an SSI variable that I set in each page:

page1.html:

<!--#set var="TITLE" value="first page" -->
<!--#include file="header.html" -->

Then I”m modifying header.html to use that variable:

<title>My site - <!--#echo var="TITLE" --></title>

This works fine but, of course, it has the unfortunate effect that, if TITLE is not set, the result is:

<title>My site - (none)</title>

So I'm trying a variety of attempts at conditionally echoing that variable depending on whether it's none or not (e.g.,  ... ) …but nothing seems to work.

Seems like this would be quite a common requirement. Does anyone have a reference to a working solution?

score 5 · Answer 1 · answered Oct 25 '16 at 04:04

5

For Apache 2.4 the expressions have changed:

<!--#if expr="-z v('CONTENT_LANGUAGE')"-->
<!--#set var="CONTENT_LANGUAGE" value="en"-->
<!--#endif-->

answered Oct 25 '16 at 04:04

jwigley

51
1
2

1

I came here looking for how to do this in httpd 2.4, since the syntax changed. – Christopher Schultz Nov 02 '18 at 19:27

score 1 · Answer 2 · answered Apr 12 '12 at 19:43

1

I've used this successfully:

<!--#if expr="! $CONTENT_LANGUAGE" -->
<!--#set var="CONTENT_LANGUAGE" value="en" -->
<!--#endif -->

answered Apr 12 '12 at 19:43

Benxamin

111
3

score 0 · Accepted Answer · answered Aug 01 '11 at 12:34

OK, solved it myself. For others' reference:

<!--#if expr="${TITLE}!=''" -->

is the correct syntax to use. It makes sense that you don't have to check for "(none)" since the undefined text value can be configured; I just didn't realised that occurred after checking the value, not before.

How do I conditionally handle undefined SSI variables using Apache?

3 Answers3