Add check for required commands

msfdb

@@ -906,6 +906,46 @@ def invoke_command(commands, component, command)
   end
 end
 
+# Searches the user's path for the executable file that would be run had the
+# command actually been invoked.
+# @param cmd [String] command name
+# @param return_all [Boolean] If true, returns a list of all instances of
+# executable found (instead of just the first one). Default: false.
+# @return [Array] instance or instances of executable found based on return_all, or nil.
+def which(cmd, return_all: false)
+  return nil if cmd.empty?
+
+  found = []
+  ENV['PATH'].split(File::PATH_SEPARATOR).each do |path|
+    exe_file = File.join(path, cmd)
+    found << exe_file if !File.directory?(exe_file) && File.executable?(exe_file)
+    break if !return_all && found.size > 0
+  end
+
+  return found.empty? ? nil : found
+end
+
+def has_requirements
+  ret_val = true
+  postgresql_cmds = %w(psql pg_ctl initdb createdb)
+  other_cmds = %w(bundle thin)
+  missing_msg = 'Missing requirement: %<name>s does not appear to be installed or is not in the environment path'
+
+  unless postgresql_cmds.all? { |cmd| !which(cmd).nil? }
+    puts missing_msg % { name: 'PostgreSQL' }
+    ret_val = false
+  end
+
+  other_cmds.each do |cmd|
+    if which(cmd).nil?
+      puts missing_msg % { name: "'#{cmd}'" }
+      ret_val = false
+    end
+  end
+
+  ret_val
+end
+
 
 
 if $PROGRAM_NAME == __FILE__
@@ -915,6 +955,10 @@ if $PROGRAM_NAME == __FILE__
     abort
   end
 
+  unless has_requirements
+    abort
+  end
+
   # map component commands to methods
   commands = {
       database: {