This document only describes the library user control interface, which doesn’t cover the actual logging, aimed at library developers.

For debugging purposes, libcasio has a debugging interface that allows displaying messages in the debug stream (usually stderr) with four different levels (plus a special one):


Debug information.




Non-fatal errors.


Fatal errors.


Special log level not to print messages.

Each level includes the message from the levels below in the list.

The log level used to be hardcoded into the library (with the configure script), but it appeared that some users wanted to be able to control it from the utilities using the library (with a --log option).

This interface is declared in <libcasio/log.h>. For forward compatibility purposes, it works with strings.

void casio_setlog(char const *level)

Set the log level using its name. Setting a log level unknown to the library will result in setting the log level to none.

char const *casio_getlog(void)

Get a pointer to the current log level (which you shall not free).

Before setting the log level, you should list the recognized log levels. It is recommended to iterate on them using the following functions for this:

int casio_iter_log(tio_iter_t **iter)

Get a log level iterator.

int casio_next_log(tio_iter_t *iter, char const **ptr)

Get the next log level on the iterator.

An example log level listing is the following:

#include <stdio.h>
#include <stdlib.h>
#include <libcasio.h>

void callback(void *cookie, const char *str)
        (void)cookie; /* no, cookie, we don't want to use you */
        printf("- %s\n", str);

int main(void)
        printf("Available log levels:\n");
        casio_listlog(&callback, NULL);
        return (0);