Shell Command Output in Macros

A definition of the form:

MACRO :sh = command

sets the value of MACRO to the standard output of the indicated command, NEWLINE characters being replaced with SPACE characters. The command is performed just once, when the definition is read. Standard error output is ignored, and make halts with an error if the command returns a non-zero exit status.

A macro reference of the form:

$(MACRO :sh)

expands to the output of the command line stored in the value of MACRO, whenever the reference is evaluated. NEWLINE characters are replaced with SPACE characters, standard error output is ignored, and make halts with an error if the command returns a non-zero exit status.