Documentation: Core / IPP (Pass 1)

Introduction Frontends Backends Includes Auxilliaries
ipp - Include Pre-Processor

NAME

ipp - Include Pre-Processor

SYNOPSIS

ipp [-D name=value] [-S includedir] [-I includedir] [-s includefile] [-i includefile] [-M options] [-P path] [-m mapfile] [-N nosynclines] [-o outputfile] [-v] inputfile ...

DESCRIPTION

The ipp program reads all inputfiles and recursively expands all

directives by substituting the directive with the contents of the file.  The
output is send to stdout or to outputfile. The files are searched
according to the following scheme:




#include 'file'




The file is searched in the current working directory only. Use
this to force the loading of a local file.





#include ``file''




The file is searched in all directories given by the -I option in the
right-to-left order they are specified on the command line.  Note that
a -I . implicit option is automatically appended to command-line
options, then files are first searched in current directory.





#include <file>




First the file is searched in the system wide ipp include directory
specified with the -S option. Second if it was not not found there it is
searched for in all directories given by the -I option.







And it provides eight additional features:






Using Wildcards


These characters have a special meaning in filenames:



If you want to include all your templates, you may write


With the following parameters you can control the order and the number
of included files using the #include 'pattern' directive:




IPP_SORT=scheme     Specify a sort criterion to include files.
          There are actually 3 different criteria : date (files are
          sorted according to their last modification time), name
          (this is the default) and numeric (filenames are sorted
          numerically).


IPP_REVERSE=scheme  As above, but resulting list of filenames
          is sorted in reverse order.


IPP_MAX=nmax        Only nmax files are included.




If you want to include the 5 newest include files of the news directory
with file names like 20000131.inc, you may write:


In the files included with the #include 'pattern' directive, the
following variables are set and can be read using $(name):




IPP_THIS  the full name of the included source file including
                       path and extension


IPP_PREV  the full name of the previous included file, unset
                       in the first file


IPP_NEXT  the full name of the next included file, unset
                       in the last file




Keep in mind that a directive without wildcards does not set these
variables.






Special `Use' Variant


In analogon to Perl's use statement, ipp provides a special variant of
#include:


This internally is equivalent to the directive


plus the special semantic that the include file is included (=used) only once,
i.e. multiple inclusion is automatically avoided. In other words


results in three inclusions of 'file'. Two from the #include's and only
once from the #use directives.






Special `Depends' Variant


You can easily write fragments of Makefiles with the -M flag (see
below) to keep tracks of which files the output file depends on, When
ipp is invoked as a piece of WML, the final output file may depend
on other files.  You can tell ipp about these hidden dependencies by
using the #depends variant , e.g.


The contents of the file is not inserted, only informations about
dependencies are updated.






Input Line Synchronization


All include commands insert some special stuff to help WML keeping
track of input line numbers.  This feature may be disabled by appending
the string IPP_NOSYNCLINES to the #include (or its variants)
command.  See also the -N flag.






Include Variables


You can add


   name[=value]


pairs at the end of #include (and #use) directives to let $(name)
interpolate to value (or 1 if =value is missing) in this include file
and all its recursively included files.


There are the following forms of the $(name) syntax, similar to the
functionality any Bourne Shell provides:




o $(name)



`Use Only Value': The standard interpolation.






 if (exists(name))
     expandto(valueof(name))
 else
     expandto("")





o $(name=string)



`Assign Value': Set a variable.






 name := string





o $(name:-string)



`Use Default String': The standard interpolation
with a default value.






 if (exists(name))
     expandto(valueof(name))
 else
     expandto(string)





o $(name:=string)



`Use Default String and Assign': The standard interpolation with a default
value and additional assignment for later use.






 if (exists(name))
     expandto(valueof(name))
 else
     expandto(string)
     name := string





o $(name:+string)



`Use Alternate String'. The replacement interpolation.






 if (exists(name))
     expandto(string)
 else
     expandto("")





o $(name:*string)



`Use Negative Alternate String'. The replacement interpolation with negated
logic.






 if (exists(name))
     expandto("")
 else
     expandto(string)





o $(name:?string)



`Indicate Error If Unset'. The error message interpolation. This can also be
used in conjunction with the above variants.






 if (exists(name))
     expandto(valueof(name))
 else
     Error(string)







Previous constructs may be nested when variable expansion contains no
parenthesis. You may for instance need these forms:


`Set a variable if unset'.


  $(var=$(var:-string))


`Redefine a variable if it is already set.'


  $(var=$(var:+string))


Notice that nested expressions are not handled as shells do. In shells
expressions are treated from left to right, whereas ipp treat inner
expressions first. With this example below


  $(foo=bar)
  $(foo:-$(foo=quux))


Bourne shells will show bar whereas ipp will print quux.


It is also possible to undefine a variable. To do so, assign an empty
value to this variable, e.g.


  $(foo=)


Notice the possibility to do simple If-Then-Else constructs:


  $(foo:+string_when_set)$(foo:*string_when_not_set)


This is equivalent to the following pseudo-code:


  if (exists(foo))
      expandto(string_when_set)
  else
      expandto(string_when_not_set)






Implicit IPP Variables


The strings __FILE__ and __LINE__ are always substituted by the
currently processed include file and the current line number.






Comments


IPP provides support for up-to-end-of-line comments.
This type of comment is like the one found in Bourne-Shell or Perl, i.e. any
line which starts with a sharp symbol (`#') is entirely (i.e. including the
newline at the end) removed from the input. Additionally these lines can have
whitespaces in front of the sharp symbol. When you really need a sharp symbol
at the start of a line you can use \#, i.e. prefix it with an escaping
backslash.






End-Of-File Stopping


It stops processing the current include file when a line containing just


  __END__


occurs. Use this to append POD documents to include files for documentation
purposes as in Perl. You can use __END__ in constructs like
$(SHORTENING:+__END__), so that the processing is only stopped
when the variable SHORTENING is set.






End-Of-Line Continuation


It removes all occurences of the pattern


  \<whitespace>*<newline><whitespace>*


Use this to let one or more lines to be concatenated.








OPTIONS




-D name=value



Defines a variable the for the initial inputfile the same way you define
ones with the #include for include files. The variable can be interpolated
via $(name) in all files.





-S includedir



Adds a system wide include directory. You can use this option more than once.
The files are searched in right-to-left order.





-I includedir



This adds an entry to the include path where include files are searched for.
You can use this option more than once. The files are searched in
right-to-left order. The current working directory is always appended as the
last directory to this list, and so is searched first.





-s includefile



Pre-load a particular include file, i.e. virtually adds a










in front of inputfile. Use this to automatically load default system
include files. You can also use the syntax type::category::file
which leads to a virtually added









-i includefile




Pre-loads a particular include file, i.e. virtually adds a










in front of inputfile. Use this to automatically load default user include
files.   You can also use the syntax type::category::file which leads to a
virtually added









-M options




Output a rule suitable for `make' describing the dependencies of each output
file, as `gcc' does. It has only sense when the -o option is used.






The D flag option writes the rule to a dependency file. The name of
this file is obtained by replacing the suffix of the output file by ``.d''.






The M flag option deletes the system files from the list of dependencies.





-P path




This sets up one or more prolog program path which are applied to each
single input file just before real processing starts. Use this to pre-process
the data.  Each program receives the data to act on as STDIN and has to
produce the filtered data on STDOUT.





-m mapfile




This adds an entry to the list of mapfiles where a mapping between obsolete
include file names and current ones can be found.  You can use this option
more than once. The mapfiles can contain the following lines:






   <blank line>
   <oldname>[,<oldname>] <newname> \[S|W|E: <text>\]






Example:






   <std/headfoot.wml>,wml::std::headfoot wml::OBSOLETE::std::headfoot [S]





-N nosynclines



By default, WML inserts some instructions to synchronize line numbers,
which are then interpreted in passes 2 and 3. This option disables this
feature.





-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 ``-''.





-v



This sets verbose mode where some processing information will be given on the
console.













AUTHORS


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


 Denis Barbier
 barbier@engelschall.com