How to see which apache modules are installed?

If you are using some kind of a unix system you probably have apache running somewhere. Sometimes you need to know which apache modules you have installed. There is a quick way to do this. 

To view the compiled modules:

> httpd -l 

Compiled in modules:

  core.c

  prefork.c

  http_core.c

  mod_so.c

To view the loaded modules:

> httpd -M 

Loaded Modules:

 core_module (static)

 mpm_prefork_module (static)

 http_module (static)

 so_module (static)

 authn_file_module (shared)

 authn_dbm_module (shared)

 authn_anon_module (shared)

 authn_dbd_module (shared)

 authn_default_module (shared)

 authz_host_module (shared)

... (this list is very long so I'm only showing the top 10)