ccze-plugin man page

ccze — A robust log colorizer, plugin infrastructure

Synopsis

#include <ccze.h>

/* Plugin support */
typedef void (*ccze_plugin_startup_t) (void);
typedef void (*ccze_plugin_shutdown_t) (void);
typedef int (*ccze_plugin_handle_t) (const char *str, size_t length, char **rest);

CCZE_DEFINE_PLUGIN (name, type, desc);
CCZE_DEFINE_PLUGINS (plugins...);

/* Display */
void ccze_addstr (ccze_color_t col, const char *str);
void ccze_newline (void);
void ccze_space (void);
void ccze_wordcolor_process_one (char *word, int slookup);

/* Helpers */
ccze_color_t ccze_http_action (const char *method);
void ccze_print_date (const char *date);

/* Command line */
char **ccze_plugin_argv_get (const char *name);
const char *ccze_plugin_name_get (void);

Description

This manual page attempts to outline the internals of CCZE plugins: how they work, how they are implemented, and how to add new ones.

There are four required entry points in a plugin: a startup, a shutdown and a handler routine (more on these later), and an informational structure.

The startup function must be of type ccze_plugin_startup_t. This is called right after the module is loaded. Its purpose is to initialise all kinds of module-specific global variables, such as the regular expressions.

The shutdown function is its counterpart: this is used to deallocate any memory reserved by the startup code.

The core part of a plugin is the handler, of type ccze_plugin_handle_t. This does the actual coloring. The string to process is passed in the str argument, its length in length. The third argument, rest is a pointer to a string. Unlike the first two, this argument is used only for output.

When a handler processed a string, it must return a non-zero value, in case it could not process it, the handler must return with zero. If the string could be processed only partially, the part which was deemed unknown by the handler must be passed back in the rest variable.

The fourth part, although the smallest part, is the most important. Without this, the module is useless, it cannot be loaded. This part tells CCZE what the startup, shutdown and handler functions are called.

To encourage good style, the little details of this structure will not be disclosed in this manual page. Instead, the helper macro, CCZE_DEFINE_PLUGIN will be explained.

CCZE_DEFINE_PLUGIN is the macro to use if one wants to make the plugin loadable. Its first argument is an unquoted string: the name of the plugin. The second part is the type of the plugin, it can be FULL, PARTIAL or ANY. The last argument is a short description of the plugin.

It is assumed that the three functions mentioned earlier are called ccze_name_setup, ccze_name_shutdown and ccze_name_handle, respectively.

A FULL plugin is one that accepts raw input, untouched by any other plugin before, and processes it. On the other hand, a PARTIAL plugin relies on previous ones preprocessing the input. For example, syslog is a full plugin, on which ulogd, a partial plugin relies. The syslog plugin processes the raw input from the logfile, adds colour to most of it, save the actual message sent by a process, that is left to subsequent plugins, like ulogd. An ANY plugin is one can act as both other types.

With CCZE_DEFINE_PLUGINS one can place more than one plugin into one shared object.

There are two other helper functions, ccze_plugin_argv_get and ccze_plugin_name_get. One can pass arguments to CCZE plugins, and these is the function to retrieve them. While ccze_plugin_name_get returns the name of the current plugin, ccze_plugin_argv_get returns a NULL-terminated array, with each entry containing an argument.

Display Methods

The so-called display methods are the only supported interface to emit something to the display. These handle both the normal, ncurses-based, and the HTML output. This is a kind of abstraction so plugins will not have to worry about the differences between the output formats.

The most important one is ccze_addstr, which takes a color (see ccze.h for a list of supported color tags) and a string, and displays it appropriately. The ccze_space and ccze_newline functions emit a space and a newline, respectively.

Our last function, ccze_wordcolor_process_one passes word to the word colourising engine. If the second argument, slookup is non-zero, the engine will perform service lookups (like getent and friends).

Helper Methods

We only have two helper methods: ccze_print_date, which simply prints out the date in the appropriate colour, and ccze_http_action, which given a HTTP method, returns the associated colour, in a format suitable for ccze_addstr.

Example

#include <ccze.h>
#include <stddef.h>
#include <string.h>

static char **ccze_foo_argv;

static int
ccze_foo_handle (const char *str, size_t length, char **rest)
{
  int i = 1;

  if (strstr (str, "foo"))
    {
      ccze_addstr (CCZE_COLOR_GOODWORD, str);
      return 1;
    }

  while (ccze_foo_argv[i])
    {
      if (strstr (str, ccze_foo_argv[i]))
        {
          ccze_addstr (CCZE_COLOR_GOODWORD, str);
          return 1;
        }
      i++;
    }
  return 0;
}

static void
ccze_foo_startup (void)
{
  ccze_foo_argv = ccze_plugin_argv_get (ccze_plugin_name_get ());
}

static void
ccze_foo_shutdown (void)
{
}

CCZE_DEFINE_PLUGIN (foo, PARTIAL, "Partial FOO coloriser.");

See Also

ccze(1)

Author

ccze was written by Gergely Nagy <algernon@bonehunter.rulez.org>, based on colorize by Istvan Karaszi <colorize@spam.raszi.hu>.

Info

2003-03-29 CCZE 0.2.1 CCZE