#echo

You can use the #echo directive to reference environment variables.

For example, suppose you have set the environment variable $cat (for "category") in a high-level web page specification file:

#set cat = "Reference"

...

#include <files/pikt/doc_page_top_files.cfg>

...

You could then reference the value of the $cat environment variable in the doc_page_top_files.cfg file in this way:

#echo "	=h1($cat)"

In any of the config files, you may reference an environment variable specified in an earlier #set or #setenv directive in this way:

#include [/bin/echo "$foo"]

which would have the same effect as the line

bar

assuming you had set foo equal to "bar" in an earlier #set or #setenv directive.

Alternatively, you could use the #echo directive:

#echo "$foo"

This would be useful to achieve a form of crude parameter passing to #include files.

Returning to the web pages example, suppose you have a common header #include file that is mainly identical across all of your pages except for a few details, such as the page title.  If you set the environment variable $title with the directive

#set title = "ACME Widgets: Product Information"

you may subsequently reference $title in the header #include file with the directive

#echo "<title>$title</title>"

After all preprocessing, the line would effectively be

<title>ACME Widgets: Product Information</title>

See the pikt.org website for demonstrations of this advanced technique.

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