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

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; }