divert(3)							     EN Tools								 divert(3)

NAME

       Divert - Text Diversion Filter

SYNOPSIS

       divert [-o outputfile] [-q] [-v] [inputfile]

DESCRIPTION

       The divert program reads inputfile or from "stdin" and applies a 2-pass diversion filter to its contents. In pass 1 all diversion locations
       are accumulated and in pass 2 these locations are recursively expanded at their dump positions.	The diversion filter is controlled by
       directives found in the input data:

       {#NAME#} (or <<NAME>>)
	   This defines the dump position of the location NAME. All accumulated data which finally has to been diverted to NAME is inserted at
	   this data position.	Notice: the final data of a location NAME has not to be known at this point, because the expansion of such
	   location dumps are done in pass 2.  You can also dump a location more than once, but the contents is always the same, independent of
	   the data position where the location dump tag stays.  The NAME can be any symbolic name matching "[a-zA-Z][a-zA-Z0-9_]*".

       {#[!]NAME[!]#: (or ..[!]NAME[!]>>)
	   This enters the location NAME (or diverts the data flow to it, hence the name for this filter).  In other words: the data flow now goes
	   on at location NAME. All following data (up to end of file or the next location leave tag) gets appended to location NAME. You can nest
	   diversions by entering other locations at any point, because the locations are remembered on a stack. The default entered location is
	   named ``"main"''. The top most location is named ``"null"'' which neither can be entered nor leaved explicitly. But of course the
	   ``"null"'' diversion can be manually dumped, for instance when using it for error messages.

	   There are two special features for diverting data which are controlled by the ""!"" characters preceding or following the NAME
	   identifier:

	   !NAME
	       This sets the data flow position to the begin of location NAME, i.e. it actually discards the current (already diverted) contents
	       of location NAME before entering it. Use this to overwrite a locations contents.

	   NAME!
	       This marks this location entry as overwritable, i.e. it enters location NAME but when the corresponding leave tag is found, the
	       data-flow position for NAME gets automatically reset to its begin. Use this if you want to set the default contents for a location
	       which only gets used if no other diversions occur to it (because any following diversions to this location will be overwrite the
	       contents). This feature is usually used for a template scheme.

	   !NAME!
	       Just the combination of the above two features. Use this to both discard the current contents of location NAME and set a new
	       default for it.

       :#[NAME]#} (or <<[NAME]..)
	   This leaves the current location, i.e. enters again the location which was active when this location was entered.  There is no need to
	   leave all locations at the end of the input data. All still entered locations are automatically left at end of file because this is
	   essential for a template scheme.

       Notice that there are two ways of using (and thinking) about the filtering mechanism this program provides:

       Macro Mechanism
	   This is the "predefined" way of thinking here. Use it like this:

	     FOO
	     {#BAR#}
	     QUUX
	     {#BAR#:
	     BAZ
	     :##}

	   Here you are thinking of the mechanism as a macro mechanism where you expand a macro at one data position while you define it via begin
	   and end tags.

       Diversion Mechanism
	   This is the alternative way of thinking. Use it like this:

	     FOO
	     <<BAR>>
	     QUUX
	     ..BAR>>
	     BAZ
	     <<..

	   In other words: You are thinking of the mechanism as a diversion mechanism where you dump a location at one data position while you
	   divert to it by entering end leaving the location (here BAR) at other positions.

       You can even intermix both ways because both are just alternative syntax variants which are treated the same.

EXAMPLE

	 {#HEAD#}
	 {#BODY#}
	 {#FOOT#}

	 {#FOOT#:
	 Quux
	 :##}

	 {#BODY#:
	 Bar
	 :##}

	 {#HEAD#:
	 Foo
	 :##}

OPTIONS

       -o outputfile
	   This redirects the output to outputfile. Usually the output will be send to stdout if no such option is specified or outputfile is
	   ``"-"''.

       -q  This sets quiet mode where warnings are suppressed.

       -v  This sets verbose mode where some processing information will be given on stderr.

AUTHORS

	Ralf S. Engelschall
	rse@engelschall.com
	www.engelschall.com

	Denis Barbier
	barbier@engelschall.com

EN Tools							    2014-04-16								 divert(3)