How do I use shell variables in Makefile actions?

Question

I have the following in a Makefile for the purpose of recreating my database including destroying it if necessary. It does not work.

.PHONY: rebuilddb     exists=$(psql postgres --tuples-only --no-align --command "SELECT 1 FROM pg_database WHERE datname='the_db'")     if [ $(exists) -eq 1 ]; then         dropdb the_db     fi     createdb -E UTF8 the_db 

Running it results in an error:

$ make rebuilddb exists= if [  -eq 1 ]; then /bin/sh: -c: line 1: syntax error: unexpected end of file make: *** [rebuilddb_postgres] Error 2 

Why is this wrong? It looks like valid Bash as far as I can tell? Are there special considerations I must make when doing this in a Makefile?

UPDATE:

Using the answer I arrived at a working version:

.PHONY: rebuilddb     exists=$$(psql postgres --tuples-only --no-align --command "SELECT 1 FROM pg_database WHERE datname='the_db'"); \     if [ "$$exists" == "1" ]; then \         dropdb the_db; \     fi;     createdb -E UTF8 the_db 

Answer 1

There are at least two considerations. $() references a Make variable. You must escape the $ to do command substitution. Also, the shell commands must be all on one line. Try:

exists=$$(psql postgres --tuples-only --no-align --command "SELECT 1 FROM \     pg_database WHERE datname='the_db'"); \     if [ "$$exists" -eq 1 ]; then \         dropdb the_db; \     fi; \     createdb -E UTF8 the_db 

On the other hand, it seems like it would be simpler to just always try to drop the database, and allow failure:

rebuilddb:     -dropdb the_db  # Leading - instructs make to not abort on error     createdb -E UTF8 the_db