Dialyzer is a tool that does static analysis of your erlang code. It’s great for identifying type errors and unreachable code. Here’s how to use it from the command line.

dialyzer -r PATH/TO/APP -I PATH/TO/INCLUDE

Pretty simple! PATH/TO/APP should be an erlang application directory containing your ebin/ and/or src/ directories. PATH/TO/INCLUDE should be a path to a directory that contains any .hrl files that need to be included. The -I is optional if you have no include files. You can have as many -r and -I options as you need. If you add -q, then dialyzer runs more quietly, succeeding silently or reporting any errors found.

If you have a test/ directory with Common Test suites, then you’ll want to add “-I /usr/lib/erlang/lib/test_server*/include/” and “-I /usr/lib/erlang/lib/common_test*/include/”. I’ve actually set this up in my Makefile to run as make check. It’s been great for catching bad return types, misspellings, and wrong function parameters.