package vlt

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This module defines the concept of layout, that is how an event is rendered into a string. It is possible to register new layouts through the register function. Initially, all the layouts defined in this file (except pattern and csv) are registered (using the function name as the registration name).

Definitions
type t = string list * string list * (Event.t -> string)

The type of layouts, the components being:

  • the header written before any event (and possibly at each rotation, if any);
  • the footer written after all event (and possibly at each rotation, if any);
  • the function actually converting the event into a string.

However, the exact semantics of each element is highly output-dependent.

val register : string -> t -> unit

register n l registers the layout l with name n, replacing any existing layout with the same name.

val register_unnamed : t -> string

Similar to register except that an unused name is generated and returned.

val get : string -> t

get n returns the layout registered with name n.

Raises Not_found if no layout exists with the passed name.

Predefined layouts
val minimal : t

The layout initially registered with the name "minimal".

Format: 

MESSAGE
val simple : t

The layout initially registered with the name "simple".

Format: 

LEVEL - MESSAGE
val default : t

The layout initially registered with the name "default".

Format: 

TIME [FILE LINE] LEVEL MESSAGE
val pattern : string list -> string list -> string -> t

pattern h f r constructs a layout (h, f, r') where r' is the rendering function defined by the string r. The rendering is done by substituting the substring of the form "$(key)" or "$(key:pad)" with their associated values. The key/value associations are as defined by the function Event.bindings. The absolute value of pad defines the minimum size of the value when rendered. Moreover, if pad is negative padding spaces are added on the left while they are added to the right if pad is positive.

val html : t

The layout initially registered with the name "html". Renders the log events into an html table.

val csv : string -> string list -> t

csv sep l constructs a layout ([], [], f) where f is the rendering function defined by:

  • sep the CSV separator;
  • l the list of elements (referred to through keys) to output for each CSV record, (the available keys are those defined by Event.bindings).