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Wiki page log-levels.md changed with summary [] by Gareth Halfacree
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---
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~~Title: Log Levels~~
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~~Title: Error Logging~~
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---
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# Log Levels #
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# Error Logging #
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EFL uses a common method to log error messages, called ``Eina_Log``, which allows you to adjust the verbosity of the logs using environment variables.
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@ -68,109 +68,18 @@ EINA_LOG_LEVEL={N} EINA_LOG_LEVELS_GLOB=eina_*:0 ./{application}
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Removing these internal logs from the output makes it easier for you to see your own domain messages.
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## Eina_Log_Print() ##
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### Aborting on Selected Log Level ##
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``Eina`` provides ``eina_log_print()``, a standard function to manage all logging messages. This function may be called directly or using helper macros including ``EINA_LOG_DBG()``, ``EINA_LOG_ERR()`` or those that take a specific domain as an argument as with ``EINA_LOG_DOM_DBG()`` and ``EINA_LOG_DOM_ERR()``. Internally, ``eina_log_print()`` will call the function defined with ``eina_log_print_cb_set()``, which defaults to ``eina_log_print_cb_stderr()`` but may be changed to do whatever you need such as networking or syslog logging.
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As well as controlling the logs themselves, the respective log levels can be used to close a program - calling ``abort()`` - once a message of a given level is logged, allowing you to automatically terminate execution. This is toggled through the environment variable ``EINA_LOG_ABORT``, while the level to be considered critical - and thus terminate execution - through the environment variable ``EINA_LOG_ABORT_LEVEL``.
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The logging system is thread-safe once initialized with ``eina_log_threads_enable()``. The thread that calls this function first is considered "main thread" and other threads will have their thread id (``pthread_self()``) printed in the log message so it is easy to detect from where the messages are coming.
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> **NOTE:**
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> Aborting at a particular log level can also be controlled from within the application itself using the ``eina_log_abort_on_critical_set()`` and ``eina_log_abort_on_critical_level_set()`` functions.
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The different logging levels serve to customize the amount of debugging information and may be used to automatically call ``abort()`` once a message of a given level is printed. This is controlled by the environment variable ``EINA_LOG_ABORT`` and the level to be considered critical with ``EINA_LOG_ABORT_LEVEL``. These can be changed with ``eina_log_abort_on_critical_set()`` and ``eina_log_abort_on_critical_level_set()``.
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```bash
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EINA_LOG_ABORT_LEVEL={N} EINA_LOG_ABORT ./{application}
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```
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The default maximum level to print is defined by the environment variable ``EINA_LOG_LEVEL`` but may be set per-domain with ``EINA_LOG_LEVELS``. It will default to ``EINA_LOG_ERR``. This can be changed with ``eina_log_level_set()``.
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## Further Reading ##
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To use the log system ``Eina`` must be initialized with ``eina_init()`` and later shut down with ``eina_shutdown()``.
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### Controlling Print Callbacks ###
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The log module allows the user to change the way ``eina_log_print()`` displays messages. It suffices to pass to ``eina_log_print_cb_set()`` the function used to display the message. That function must be of type ``#Eina_Log_Print_Cb``. As custom data can be passed to that callback, customized messages can be displayed.
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It is suggested to not use ``__FILE__``, ``__FUNCTION__`` or ``__LINE__`` when writing that callback, but when defining macros like ``EINA_LOG_ERR()`` and others.
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## Logging from an Application ##
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The following example, available for download from the [Enlightenment Project git repository](https://git.enlightenment.org/tools/examples.git/tree/reference/c/eina/src/eina_log.c), demonstrates the control of logging from within an application.
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```c
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#define EFL_EO_API_SUPPORT 1
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#define EFL_BETA_API_SUPPORT 1
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#include <stdio.h>
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#include <Eina.h>
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#include <Efl_Core.h>
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/*
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* Efl Core Log examples.
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*
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* This demo shows how to log at various levels and to change what log is shown.
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* You can also use a custom log printer in your app as shown in _log_custom.
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*/
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static double
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_divide(int num, int denom)
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{
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if (denom == 0)
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EINA_LOG_CRIT("Attempt to divide by 0\n");
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else
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{
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if (denom < 0)
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EINA_LOG_WARN("Possible undesirable effect, divide by negative number");
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double ret = ((double) num / denom);
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EINA_LOG_INFO("%d / %d = %f\n", num, denom, ret);
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return ret;
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}
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return -1;
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}
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static void
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_divides()
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{
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_divide(5, 1);
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_divide(5, -1);
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_divide(5, 0);
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}
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static void
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_log_levels()
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{
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printf("Executing with default logging\n");
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_divides();
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eina_log_level_set(EINA_LOG_LEVEL_WARN);
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printf("Executing with WARN level\n"); // same as EINA_LOG_LEVEL = 2
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_divides();
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eina_log_level_set(EINA_LOG_LEVEL_INFO);
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printf("Executing with INFO on\n"); // same as EINA_LOG_LEVEL = 3
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_divides();
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}
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void _print_cb(const Eina_Log_Domain *domain EINA_UNUSED, Eina_Log_Level level,
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const char *file, const char *fnc, int line,
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const char *fmt, void *data EINA_UNUSED, va_list args)
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{
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fprintf(stdout, "LOG %d <%s (%s:%d)> ", level, fnc, file, line);
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vfprintf(stdout, fmt, args);
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putc('\n', stdout);
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}
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static void
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_log_custom()
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{
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printf("Executing with custom log printer\n");
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eina_log_print_cb_set(_print_cb, NULL);
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_divides();
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}
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EAPI_MAIN void
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efl_main(void *data EINA_UNUSED, const Efl_Event *ev EINA_UNUSED)
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{
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_log_levels();
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_log_custom();
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efl_exit(0);
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}
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EFL_MAIN()
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```
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[Eina Programming Guide: Logging](/develop/c/eina/logging.md)
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: A reference, including example, for the Eina_Log module.
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