Testing if a file exists in makefile target, and quitting if not present

Question

Is there a way to exit with an error condition if a file does not exist? I am currently doing something like this:

all: foo  foo:     test -s /opt/local/bin/gsort || echo "GNU sort does not exist! Exiting..." && exit 

Running make runs the all target, which runs foo.

The expectation is that if the test -s conditional fails, then the echo/exit statements are executed.

However, even if /usr/bin/gsort exists, I get the result of the echo statement but the exit command does not run. This is the opposite of what I am hoping to accomplish.

What is the correct way to do something like the above?

Answer 1

I realize this is a bit old at this point, but you don't need to even use a subshell to test if a file exists in Make.

It also depends on how you want/expect it to run.

Using the wildcard function, like so:

all: foo foo: ifeq (,$(wildcard /opt/local/bin/gsort))     $(error GNU Sort does not exist!) endif 

is one good way to do it. Note here that the ifeq clause is not indented because it is evaluated before the target itself.

If you want this to happen unconditionally for every target, you can just move it outside of a target:

ifeq (,$(wildcard /opt/local/bin/gsort)) $(error GNU Sort does not exist!) endif 

Answer 2

exit alone returns the status of the last command executed. In this case, it returns zero, which means everything is ok.

This is, because || and && have equal precedence, and the shell interprets the command as if it were written

( test ... || echo ... ) && exit 

If you want to signal failure you must exit with a non zero value, e.g. exit 1. And if you want to echo and exit, just put the commands in sequence separated by ;

all: foo  foo:     test -s /opt/local/bin/gsort || { echo "GNU sort does not exist! Exiting..."; exit 1; }