(make.info.gz) Substitution Refs

 
 6.3.1 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
 example:
 
      foo := a.o b.o c.o
      bar := $(foo:.o=.c)
 
 sets `bar' to `a.c b.c c.c'.   Setting Variables Setting.
 
    A substitution reference is actually an abbreviation for use of the
 `patsubst' expansion function ( Functions for String Substitution
 and Analysis Text Functions.).  We provide substitution references as
 well as `patsubst' for compatibility with other implementations of
 `make'.
 
    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))'.   Functions for
 String Substitution and Analysis Text Functions, 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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