/*! \page macros Macro syntax

RPM has fully recursive spec file macros.  Simple macros do straight text
substitution. Parameterized macros include an options field, and perform
argc/argv processing on white space separated tokens to the next newline.
During macro expansion, both flags and arguments are available as macros
which are deleted at the end of macro expansion.  Macros can be used
(almost) anywhere in a spec file, and, in particular, in "included file
lists" (i.e. those read in using %files -f <file>).  In addition, macros
can be nested, hiding the previous definition for the duration of the
expansion of the macro which contains nested macros.

\subsection macros_defining Defining a Macro

To define a macro use:

\verbatim
	%define <name>[(opts)] <body>
\endverbatim

All whitespace surrounding <body> is removed.  Name may be composed
of alphanumeric characters, and the character `_' and must be at least
3 characters in length. A macro without an (opts) field is "simple" in that
only recursive macro expansion is performed. A parameterized macro contains
an (opts) field. The opts (i.e. string between parantheses) is passed
exactly as is to getopts(3) for argc/argv processing at the beginning of
a macro invocation.  While a parameterized macro is being expanded, the
following shell-like macros are available:

\verbatim
	%0	the name of the macro being invoked
	%*	all arguments (unlike shell, not including any processed flags)
	%#	the number of arguments
	%{-f}	if present at invocation, the flag f itself
	%{-f*}	if present at invocation, the argument to flag f
	%1, %2	the arguments themselves (after getopt(3) processing)
\endverbatim

At the end of invocation of a parameterized macro, the above macros are
(at the moment, silently) discarded.

\subsection macros_writing Writing a Macro

Within the body of a macro, there are several constructs that permit
testing for the presence of optional parameters. The simplest construct
is "%{-f}" which expands (literally) to "-f" if -f was mentioned when the
macro was invoked. There are also provisions for including text if flag
was present using "%{-f:X}". This macro expands to (the expansion of) X
if the flag was present. The negative form, "%{!-f:Y}", expanding to (the
expansion of) Y if -f was *not* present, is also supported.

In addition to the "%{...}" form, shell expansion can be performed
using "%(shell command)". The expansion of "%(...)" is the output of
(the expansion of) ... fed to /bin/sh. For example, "%(date
+%%y%%m%%d)" expands to the string "YYMMDD" (final newline is
deleted). Note the 2nd % needed to escape the arguments to /bin/date.
There is currently an 8K limit on the size that this macro can expand
to.

\subsection macros_builtin Builtin Macros

There are several builtin macros (with reserved names) that are needed
to perform useful operations. The current list is

\verbatim
	%trace		toggle print of debugging information before/after
			expansion
	%dump		print the active (i.e. non-covered) macro table

	%{echo:...}	print ... to stderr
	%{warn:...}	print ... to stderr
	%{error:...}	print ... to stderr and return BADSPEC
 
	%define ...	define a macro
	%undefine ...	undefine a macro
	%global ...	define a macro whose body is available in global context

	%{uncompress:...} expand ... to <file> and test to see if <file> is
			compressed.  The expansion is
				cat <file>		# if not compressed
				gzip -dc <file>		# if gzip'ed
				bzip2 -dc <file>	# if bzip'ed
	%{expand:...}	like eval, expand ... to <body> and (re-)expand <body>

	%{S:...}	expand ... to <source> file name
	%{P:...}	expand ... to <patch> file name
	%{F:...}	expand ... to <file> file name
\endverbatim

Macros may also be automatically included from /usr/lib/rpm/macros.
In addition, rpm itself defines numerous macros. To display the current
set, add "%dump" to the beginning of any spec file, process with rpm, and
examine the output from stderr.

\subsection macros_example Example of a Macro

Here is an example %patch definition from /usr/lib/rpm/macros:

\verbatim
	%patch(b:p:P:REz:) \
	%define patch_file	%{P:%{-P:%{-P*}}%{!-P:%%PATCH0}} \
	%define patch_suffix	%{!-z:%{-b:--suffix %{-b*}}}%{!-b:%{-z:--suffix %{-z*}}}%{!-z:%{!-b: }}%{-z:%{-b:%{error:Can't specify both -z(%{-z*}) and -b(%{-b*})}}} \
		%{uncompress:%patch_file} | patch %{-p:-p%{-p*}} %patch_suffix %{-R} %{-E} \
	...
\endverbatim


The first line defines %patch with its options. The body of %patch is

\verbatim
	%{uncompress:%patch_file} | patch %{-p:-p%{-p*}} %patch_suffix %{-R} %{-E}
\endverbatim

The body contains 7 macros, which expand as follows

\verbatim
	%{uncompress:...}	copy uncompressed patch to stdout
	  %patch_file		... the name of the patch file
	%{-p:...}		if "-p N" was present, (re-)generate "-pN" flag
	  -p%{-p*}		... note patch-2.1 insists on contiguous "-pN"
	%patch_suffix		override (default) ".orig" suffix if desired
	%{-R}			supply -R (reversed) flag if desired
	%{-E}			supply -E (delete empty?) flag if desired
\endverbatim

There are two "private" helper macros:

\verbatim
	%patch_file	the gory details of generating the patch file name
	%patch_suffix	the gory details of overriding the (default) ".orig"
\endverbatim

\subsection macros_using Using a Macro

To use a macro, write:

\verbatim
	%<name> ...
\endverbatim

or

\verbatim
	%{<name>}
\endverbatim

The %{...} form allows you to place the expansion adjacent to other text.
The %<name> form, if a parameterized macro, will do argc/argv processing
of the rest of the line as described above.  Normally you will likely want
to invoke a parameterized macro by using the %<name> form so that
parameters are expanded properly.

Example:
\verbatim
	%define mymacro() (echo -n "My arg is %1" ; sleep %1 ; echo done.)
\endverbatim

Usage:

\verbatim
	%mymacro 5
\endverbatim

This expands to:

\verbatim
	(echo -n "My arg is 5" ; sleep 5 ; echo done.)
\endverbatim

This will cause all occurances of %1 in the macro definition to be
replaced by the first argument to the macro, but only if the macro
is invoked as "%mymacro 5".  Invoking as "%{mymacro} 5" will not work
as desired in this case.

\subsection macros_commandline Command Line Options

When the command line option "--define 'macroname value'" allows the
user to specify the value that a macro should have during the build.
Note lack of leading % for the macro name.  We will try to support
users who accidentally type the leading % but this should not be
relied upon.

Evaluating a macro can be difficult outside of an rpm execution context. If
you wish to see the expanded value of a macro, you may use the option
\verbatim
	--eval '<macro expression>'
\endverbatim
that will read rpm config files and print the macro expansion on stdout.

Note: This works only macros defined in rpm configuration files, not for
macros defined in specfiles. You can use %{echo: %{your_macro_here}} if
you wish to see the expansion of a macro defined in a spec file.
 
\subsection macros_configuration Configuration using Macros

Starting in rpm 3.0, macros rather than rpmrc lines are used to configure rpm.
In general, all the rpmrc configuration lines documented in "Maximum RPM"
have been converted to macros, usually with a leading underscore, and the
same name that was used in rpmrc files. In some cases, there is no leading
underscore. Those macros existed in rpm-2.5.x and the underscore is omitted
in order to preserve the meaning and usage of macros that are defined during
spec file parsing.

Here's an example to illustrate configuration using macros:

\verbatim
   Old way:
	In /etc/rpmrc and/or ~/.rpmrc you put
		something:      some_value

   New way:
	In /etc/rpm/macros and/or ~/.rpmmacros
		%_something     some_value
\endverbatim

Here are 2 common FAQ for experienced users of rpm:

\verbatim
  1) --rcfile works differently.
    Old way:	rpm --rcfile whatever
    New way:	rpm --rcfile /usr/lib/rpm/rpmrc:whatever

  2) topdir (and other rpmrc configurables) work differently.

    Old way:
	~/.rpmrc contains
		topdir:         whatever

    New way:
	/usr/lib/rpm/rpmrc contains
		macrofiles:     /usr/lib/rpm/macros: ... :~/.rpmmacros
	~/.rpmmacros contains
		%_topdir        whatever
\endverbatim

\subsection macros_autoconf Macro Analogues of Autoconf Variables

Several macro definitions provided by the default rpm macro set have uses in
packaging similar to the autoconf variables that are used in building packages:

\verbatim
    %_prefix		/usr
    %_exec_prefix	%{_prefix}
    %_bindir		%{_exec_prefix}/bin
    %_sbindir		%{_exec_prefix}/sbin
    %_libexecdir	%{_exec_prefix}/libexec
    %_datadir		%{_prefix}/share
    %_sysconfdir	%{_prefix}/etc
    %_sharedstatedir	%{_prefix}/com
    %_localstatedir	%{_prefix}/var
    %_libdir		%{_exec_prefix}/lib
    %_includedir	%{_prefix}/include
    %_oldincludedir	/usr/include
    %_infodir		%{_prefix}/info
    %_mandir		%{_prefix}/man
\endverbatim

*/
