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Formerly make.texinfo.~27~

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Roland McGrath 1992-06-12 23:12:20 +00:00
parent 87c5a97b91
commit 3dbe309fce
1 changed files with 25 additions and 6 deletions
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make.texinfo
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@ -2213,12 +2213,12 @@ foo : bar/lose
The program used as the shell is taken from the variable @code{SHELL}. The program used as the shell is taken from the variable @code{SHELL}.
By default, the program @file{/bin/sh} is used. By default, the program @file{/bin/sh} is used.
Unlike most variables, the variable @code{SHELL} will not be set from Unlike most variables, the variable @code{SHELL} is never set from the
the environment, except in a recursive @code{make}. This is because the environment. This is because the @code{SHELL} environment variable is
@code{SHELL} environment variable is used to specify your personal used to specify your personal choice of shell program for interactive
choice of shell program for interactive use. It would be very bad for use. It would be very bad for personal choices like this to affect
personal choices like this to affect the functioning of makefiles. the functioning of makefiles. @xref{Environment, ,Variables from the
@xref{Environment, ,Variables from the Environment}. Environment}.
@node Parallel, Errors, Execution, Commands @node Parallel, Errors, Execution, Commands
@section Parallel Execution @section Parallel Execution
@ -3570,6 +3570,25 @@ Expand all variable references in @var{arg1} and @var{arg2} and
compare them. If they are identical, the @var{text-if-true} is compare them. If they are identical, the @var{text-if-true} is
effective; otherwise, the @var{text-if-false}, if any, is effective. effective; otherwise, the @var{text-if-false}, if any, is effective.
Often you want to test if a variable has a non-empty value. When the
value results from complex expansions of variables and functions,
expansions you would consider empty may actually contain whitespace
characters and thus are not seen as empty. However, you can use the
@code{strip} function to avoid interpreting whitespace as a non-empty
value. For example:
@example
@group
ifeq ($(strip $(foo)),)
@var{text-if-empty}
endif
@end group
@end example
@noindent
will evaluate @var{text-if-empty} even if the expansion of
@code{$(foo)} contains whitespace characters.
@item ifneq (@var{arg1}, @var{arg2}) @item ifneq (@var{arg1}, @var{arg2})
@itemx ifneq '@var{arg1}' '@var{arg2}' @itemx ifneq '@var{arg1}' '@var{arg2}'
@itemx ifneq "@var{arg1}" "@var{arg2}" @itemx ifneq "@var{arg1}" "@var{arg2}"