(make.info)Substitution Refs

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Substitution References

   A "substitution reference" substitutes the value of a variable with
alterations that you specify.  It has the form `$(VAR:A=B)' (or
`${VAR:A=B}') and its meaning is to take the value of the variable VAR,
replace every A at the end of a word with B in that value, and
substitute the resulting string.

   When we say "at the end of a word", we mean that A must appear
either followed by whitespace or at the end of the value in order to be
replaced; other occurrences of A in the value are unaltered.  For

     foo := a.o b.o c.o
     bar := $(foo:.o=.c)

sets `bar' to `a.c b.c c.c'.  Note: Setting Variables.

   A substitution reference is actually an abbreviation for use of the
`patsubst' expansion function (Note: Functions for String Substitution
and Analysis.).  We provide substitution references as
well as `patsubst' for compatibility with other implementations of

   Another type of substitution reference lets you use the full power of
the `patsubst' function.  It has the same form `$(VAR:A=B)' described
above, except that now A must contain a single `%' character.  This
case is equivalent to `$(patsubst A,B,$(VAR))'.  Note: Functions for
String Substitution and Analysis, for a description of
the `patsubst' function.

For example:

     foo := a.o b.o c.o
     bar := $(foo:%.o=%.c)

sets `bar' to `a.c b.c c.c'.

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