libcasio/docs/logging.md

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page	logging

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):

• info (debug information);
• warn (warnings);
• error (non-fatal errors);
• fatal (fatal errors);
• none (special log level to tell 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.

To set the loglevel, use casio_setlog(), and to get a pointer to the current loglevel, use casio_getlog().

{% highlight c linenos %} void casio_setlog(const char *level); const char *casio_getlog(void); {% endhighlight %}

Setting an unknown log level will simply result in setting the log level to none.

Before setting the log level, you should list the recognized log levels. For this, use the casio_setlog() function:

{% highlight c linenos %} typedef void casio_log_list_t(void *cookie, const char *str); void casio_listlog(casio_log_list_t *callback, void *cookie); {% endhighlight %}

The callback will be called for every recognized log level. It is possible for the function to call the callback only once (see the --no-log option in Getting started).

An example log level listing is the following:

{% highlight c linenos %} #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); } {% endhighlight %}