Functions -> Shell Function

The `shell' function is unlike any other function except the `wildcard' function (*note The Function `wildcard': Wildcard Function.) in that it communicates with the world outside of `make'.

The `shell' function performs the same function that backquotes (``') perform in most shells: it does "command expansion". This means that it takes an argument that is a shell command and returns the output of the command. The only processing `make' does on the result, before substituting it into the surrounding text, is to convert each newline or carriage-return / newline pair to a single space. It also removes the trailing (carriage-return and) newline, if it's the last thing in the result.

Here are some examples of the use of the `shell' function:

contents := $(shell cat foo)
files := $(shell echo *.c)