Info Catalog make: Echoing make: Recipes make: Parallel

make: Execution

 
 5.3 Recipe Execution
 ====================
 
 When it is time to execute recipes to update a target, they are executed
 by invoking a new sub-shell for each line of the recipe, unless the
 '.ONESHELL' special target is in effect (Using One Shell One
 Shell.) (In practice, 'make' may take shortcuts that do not affect the
 results.)
 
    *Please note:* this implies that setting shell variables and invoking
 shell commands such as 'cd' that set a context local to each process
 will not affect the following lines in the recipe.(1)  If you want to
 use 'cd' to affect the next statement, put both statements in a single
 recipe line.  Then 'make' will invoke one shell to run the entire line,
 and the shell will execute the statements in sequence.  For example:
 
      foo : bar/lose
              cd $(@D) && gobble $(@F) > ../$@
 
 Here we use the shell AND operator ('&&') so that if the 'cd' command
 fails, the script will fail without trying to invoke the 'gobble'
 command in the wrong directory, which could cause problems (in this case
 it would certainly cause '../foo' to be truncated, at least).
 

Menu

 
· One Shell                   One shell for all lines in a recipe.
· Choosing the Shell          How 'make' chooses the shell used
                                   to run recipes.
 
    ---------- Footnotes ----------
 
    (1) On MS-DOS, the value of current working directory is *global*, so
 changing it _will_ affect the following recipe lines on those systems.
 

Info Catalog make: Echoing make: Recipes make: Parallel