Info Catalog m4: Inhibiting Invocation m4: Macros m4: Quoting Arguments

m4: Macro Arguments

 
 4.3 Macro arguments
 ===================
 
 When a name is seen, and it has a macro definition, it will be expanded
 as a macro.
 
    If the name is followed by an opening parenthesis, the arguments will
 be collected before the macro is called.  If too few arguments are
 supplied, the missing arguments are taken to be the empty string.
 However, some builtins are documented to behave differently for a
 missing optional argument than for an explicit empty string.  If there
 are too many arguments, the excess arguments are ignored.  Unquoted
 leading whitespace is stripped off all arguments, but whitespace
 generated by a macro expansion or occurring after a macro that expanded
 to an empty string remains intact.  Whitespace includes space, tab,
 newline, carriage return, vertical tab, and formfeed.
 
      define(`macro', `$1')
      =>
      macro( unquoted leading space lost)
      =>unquoted leading space lost
      macro(` quoted leading space kept')
      => quoted leading space kept
      macro(
       divert `unquoted space kept after expansion')
      => unquoted space kept after expansion
      macro(macro(`
      ')`whitespace from expansion kept')
      =>
      =>whitespace from expansion kept
      macro(`unquoted trailing whitespace kept'
      )
      =>unquoted trailing whitespace kept
      =>
 
    Normally 'm4' will issue warnings if a builtin macro is called with
 an inappropriate number of arguments, but it can be suppressed with the
 '--quiet' command line option (or '--silent', or '-Q', ⇒Invoking
 m4 Operation modes.).  For user defined macros, there is no check of
 the number of arguments given.
 
      $ m4
      index(`abc')
      error->m4:stdin:1: Warning: too few arguments to builtin `index'
      =>0
      index(`abc',)
      =>0
      index(`abc', `b', `ignored')
      error->m4:stdin:3: Warning: excess arguments to builtin `index' ignored
      =>1
 
      $ m4 -Q
      index(`abc')
      =>0
      index(`abc',)
      =>0
      index(`abc', `b', `ignored')
      =>1
 
    Macros are expanded normally during argument collection, and whatever
 commas, quotes and parentheses that might show up in the resulting
 expanded text will serve to define the arguments as well.  Thus, if FOO
 expands to ', b, c', the macro call
 
      bar(a foo, d)
 
 is a macro call with four arguments, which are 'a ', 'b', 'c' and 'd'.
 To understand why the first argument contains whitespace, remember that
 unquoted leading whitespace is never part of an argument, but trailing
 whitespace always is.
 
    It is possible for a macro's definition to change during argument
 collection, in which case the expansion uses the definition that was in
 effect at the time the opening '(' was seen.
 
      define(`f', `1')
      =>
      f(define(`f', `2'))
      =>1
      f
      =>2
 
    It is an error if the end of file occurs while collecting arguments.
 
      hello world
      =>hello world
      define(
      ^D
      error->m4:stdin:2: ERROR: end of file in argument list
 

Info Catalog m4: Inhibiting Invocation m4: Macros m4: Quoting Arguments