Run-time information about CAPS

Take a look into the caps.pc file:

# required but I don't know why, yet.
prefix = /

# generic CAPS config
caps_config_path=${prefix}/etc/caps
# Driver Configuration Directory
caps_driver_runtime_config_path=/etc/caps/drivers

# Device Database Directory
caps_device_database_path=/var/lib/caps
# Device Parameter Directory
caps_device_param_path=/var/lib/caps

# Driver Database Directory (VID/PID to driver relation)
caps_driverdatabase_path=/usr/share/caps/drivers

# Driver Executables Directory
caps_driver_path=/usr/libexec/caps

# Document storage
caps_document_storage_path=/var/spool/caps

# CAPS user ID with the most permissions
caps_user_id_root=0

# CAPS user ID with restricted permissions (regular user)
caps_user_id_caps=150

# CAPS group ID for a regular user
caps_group_id_caps=150

Name: CAPS
Description: CAPS printing universe
Version: 1.0.0
URL: http://www.caps-printing.org

Or ask pkgconfig for the details:

$ pkg-config --variable=caps_config_path caps
/etc/caps

You should never guess these paths, always use pkgconfig for it. And you do not need it by your own in your configure.ac. You can use already existing M4 macros instead.