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* doc/make.texi (Text Functions): [SV 64339] Clarify pattern use.

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Paul Smith 2024-01-07 10:22:20 -05:00
parent a80670ad41
commit 1161779ef8
1 changed files with 31 additions and 21 deletions
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doc/make.texi
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@ -7519,15 +7519,17 @@ produces the value @samp{fEEt on the strEEt}.
@item $(patsubst @var{pattern},@var{replacement},@var{text})
@findex patsubst
Finds whitespace-separated words in @var{text} that match
@var{pattern} and replaces them with @var{replacement}. Here
@var{pattern} may contain a @samp{%} which acts as a wildcard,
matching any number of any characters within a word. If
@var{replacement} also contains a @samp{%}, the @samp{%} is replaced
by the text that matched the @samp{%} in @var{pattern}. Words that do
not match the pattern are kept without change in the output. Only the
first @samp{%} in the @var{pattern} and @var{replacement} is treated
this way; any subsequent @samp{%} is unchanged.
Finds whitespace-separated words in @var{text} that match @var{pattern} and
replaces them with @var{replacement}. Here @var{pattern} may contain a
@samp{%} which acts as a wildcard, matching any number of any characters
within a word. If @var{replacement} also contains a @samp{%}, the @samp{%} is
replaced by the text that matched the @samp{%} in @var{pattern}. Words that
do not match the pattern are kept without change in the output. Only the
first @samp{%} in the @var{pattern} and @var{replacement} is treated this way;
any subsequent @samp{%} is unchanged.
If @var{pattern} does not contain a @samp{%} then the entire word must compare
equal to be a match.
@cindex @code{%}, quoting in @code{patsubst}
@cindex @code{\} (backslash), to quote @code{%}
@ -7555,7 +7557,14 @@ $(patsubst %.c,%.o,x.c.c bar.c)
@end example
@noindent
produces the value @samp{x.c.o bar.o}.
produces the value @samp{x.c.o bar.o}, while
@example
$(patsubst foo.c,foo.o,foo.c foobar.c)
@end example
@noindent
produces the value @samp{foo.o foobar.c}.
Substitution references (@pxref{Substitution Refs, ,Substitution
References}) are a simpler way to get the effect of the @code{patsubst}
@ -7618,11 +7627,8 @@ respectively. @xref{Testing Flags}, for a practical application of
@item $(filter @var{pattern}@dots{},@var{text})
Returns all whitespace-separated words in @var{text} that @emph{do} match
any of the @var{pattern} words, removing any words that @emph{do not}
match. The patterns are written using @samp{%}, just like the patterns
used in the @code{patsubst} function above.
The @code{filter} function can be used to separate out different types
of strings (such as file names) in a variable. For example:
match. Each word in @var{pattern} is compared to every word in @var{text}
using the same algorithm as the @code{patsubst} function above.
@example
sources := foo.c bar.c baz.s ugh.h
@ -7640,17 +7646,18 @@ compiler.
@findex filter-out
@cindex filtering out words
@cindex words, filtering out
Returns all whitespace-separated words in @var{text} that @emph{do not}
match any of the @var{pattern} words, removing the words that @emph{do}
match one or more. This is the exact opposite of the @code{filter}
function.
Returns all whitespace-separated words in @var{text} that @emph{do not} match
any of the @var{pattern} words, removing the words that @emph{do} match one or
more. Each word in @var{pattern} is compared to every word in @var{text}
using the same algorithm as the @code{patsubst} function above. This is the
exact opposite of the @code{filter} function.
For example, given:
@example
@group
objects=main1.o foo.o main2.o bar.o
mains=main1.o main2.o
objects = main1.o foo.o main2.o bar.o remain1.o
mains = main1.o main2.o
@end group
@end example
@ -7662,6 +7669,9 @@ in @samp{mains}:
$(filter-out $(mains),$(objects))
@end example
@noindent
This would expand to @samp{foo.o bar.o remain1.o}.
@need 1500
@findex sort
@cindex sorting words