[ILUG] ksh question

[Brian Foster]

  | Date: Thu, 8 May 2008 14:11:26 +0100
  | From: "Braun Brelin" <bbrelin at gmail.com>
  | Someone sent me the following lines in a Makefile:
  | 
  | XML_RULE = @echo " xml-rule $< xml2hpp.xsl $@" && \
  | $(JAVA_BIN) -cp $(XT_DIR)/xp.jar:$(XT_DIR)/xt.jar \
  | com.jclark.xsl.sax.Driver \
  | $< $(CMKCMK)/xml2hpp.xsl $@
  | 
  | They wanted to know what the "$<" and "$@" symbols mean.

 the above is defining a make(1) macro called XML_RULE.

 the ‘$@’ and ‘$<’ and all the ‘$(NAME)’s are expanded
 by ‘make’ when that macro is invoked (NOT when it is
 defined).  the result of that expansion is clearly
 intended to then run by a shell.

  | The make program is running under ksh.

 so what?  I don't see anything specific to the Korn
 shell above; it looks like it'd work with most any
 Bourne-ish shell.

  | The $@ is almost certainly the builtin array $@ for command line arguments,

 NO.  not here.  it is ‘make’s $@.  the shell (Korn
 or otherwise) never sees it.  if the shell's $@ was
 meant, then in a Makefile you'd what to write it $$@
 (note the doubled $).  and similarly for $<.

  |[ ... ]
  | Anyone else know what $< is in KSH?

 AFAICR, there is $< in ksh(1).

 ‘make’ has truely awful syntax, and the semantics
 can be rather daunting at times as well.

cheers!
	-blf-
-- 
“How many surrealists does it take to    |  Brian Foster
 change a lightbulb?  Three.  One calms  |  somewhere in south of France
 the warthog, and two fill the bathtub   |     Stop E$$o (ExxonMobil)!
 with brightly-coloured machine tools.”  |       http://www.stopesso.com