Substitution references

Substitution references in GNU make provide a shorthand way to alter the value of a variable by replacing parts of its text.

They are most commonly used to transform a list of source files into a list of object files.

There are two primary types of substitution references

1. suffix substitution
2. pattern substitution

1. suffix substitution

• Syntax:

  $(var:old_suffix=new_suffix)
  

  var: The name of the variable to modify (do not use $ here).

  old_suffix: The text at the end of a word to be replaced.

  new_suffix: The text that replaces the old suffix.

• Example:

  SRC = main.c utils.c
  OBJ = $(SRC:.c=.o)
  

2. pattern substitution

• Syntax:

  $(var:pattern=replacement)
  

  var: The name of the variable to modify (do not use $ here)

  pattern: the pattern need to be replaced

  replacement: the text patten that replaces the old pattern

• Example:

  SRC = src/main.c src/utils.c
  OBJ = $(SRC:%.c=%.o)
  

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