Configuration Variables

The events library has a number of configuration variables that may be tweaked by a user or a process. Internally, it uses the treeconf configuration library to manage these variables as a tree of variable nodes. The library uses the "event.modules" node in the tree to contain configuration specific to particular engines--for instance, an engine named "dummy" may define the configuration variable "event.modules.dummy.count" to specify the number of events to transfer from the system at a time. The library itself defines a number of other variables--to define a list of loadable modules, for instance. The application may also register some variables with the treeconf configuration library through use of the event_attr_confreg() function to manipulate an event attribute structure. (See the documentation for ev_attr_t for more information on this.)

Library Configuration Variables

The library defines the following variables:

• event.libpath
  Contains the search path for library engine modules. If not specified, the package library directory (often /usr/local/lib/event) will be used. Note that tilde expansion is not performed on this variable.

• event.modlist
  Contains a space-separated list of modules to load and initialize. Each module name may optionally be followed by a colon (':') and a set of one-character flags to specify the engine components to use. The recognized flags are s (socket), i (signal), and t (timer). If not specified, a compiled-in default will be used.

Configuration File Searching

The event_init() function uses the tc_path() function to load the configuration from all the files listed in the envpath argument, which is presumed to be passed in by the application from the environment. If the envpath contains an empty field (i.e., "::"), envpath is passed as NULL, or the EV_INIT_SECURE flag is passed to event_init(), then a default path will be searched. Note that the EV_INIT_SECURE flag will also cause files containing the %n or ~ expandos to be skipped for security reasons.

In addition to the ~ expandos (~ expands to the current user's home directory; ~user expands to the home directory of user), the library also defines the %n and %p expandos, which expand to the user name and the application name, respectively. (The application name is passed as the prog argument to the event_init() function. If NULL is passed for prog, file names containing the %p expando will be omitted.)

By default, the default search path contains "event.tc" from the system package configuration directory (often /usr/local/etc/event); ".event.tc" from the user's home directory; "%p.tc" from the system configuration directory; and ".%p.tc" from the user's home directory. This default may be overridden by passing event_init() an ev_attr_t object which has been modified by a call to event_attr_confpath().

Any variables passed in an ev_attr_t (modified by a call to the event_attr_confvar() function) will override any values found in any of the configuration files loaded by event_init().

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