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make: Recursion

 
 5.7 Recursive Use of 'make'
 ===========================
 
 Recursive use of 'make' means using 'make' as a command in a makefile.
 This technique is useful when you want separate makefiles for various
 subsystems that compose a larger system.  For example, suppose you have
 a sub-directory 'subdir' which has its own makefile, and you would like
 the containing directory's makefile to run 'make' on the sub-directory.
 You can do it by writing this:
 
      subsystem:
              cd subdir && $(MAKE)
 
 or, equivalently, this (Summary of Options Options Summary.):
 
      subsystem:
              $(MAKE) -C subdir
 
    You can write recursive 'make' commands just by copying this example,
 but there are many things to know about how they work and why, and about
 how the sub-'make' relates to the top-level 'make'.  You may also find
 it useful to declare targets that invoke recursive 'make' commands as
 '.PHONY' (for more discussion on when this is useful, see Phony
 Targets).
 
    For your convenience, when GNU 'make' starts (after it has processed
 any '-C' options) it sets the variable 'CURDIR' to the pathname of the
 current working directory.  This value is never touched by 'make' again:
 in particular note that if you include files from other directories the
 value of 'CURDIR' does not change.  The value has the same precedence it
 would have if it were set in the makefile (by default, an environment
 variable 'CURDIR' will not override this value).  Note that setting this
 variable has no impact on the operation of 'make' (it does not cause
 'make' to change its working directory, for example).
 

Menu

 
· MAKE Variable               The special effects of using '$(MAKE)'.
· Variables/Recursion         How to communicate variables to a sub-'make'.
· Options/Recursion           How to communicate options to a sub-'make'.
· -w Option                   How the '-w' or '--print-directory' option
                                   helps debug use of recursive 'make' commands.
 

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