FIDO_INIT(3) Library Functions Manual FIDO_INIT(3)

fido_init, fido_set_log_handler
initialise the FIDO2 library

#include <fido.h>
typedef void fido_log_handler_t(const char *);

fido_init(int flags);
fido_set_log_handler(fido_log_handler_t *handler);

The fido_init() function initialises the libfido2 library. Its invocation must precede that of any other libfido2 function in the context of the executing thread.
If FIDO_DEBUG is set in flags, then debug output will be emitted by libfido2 on stderr. Alternatively, the FIDO_DEBUG environment variable may be set.
If FIDO_DISABLE_U2F_FALLBACK is set in flags, then libfido2 will not fallback to U2F in fido_dev_open(3) if a device claims to support FIDO2 but fails to respond to a CTAP 2.0 greeting.
The fido_set_log_handler() function causes handler to be called for each log line generated in the context of the executing thread. Lines passed to handler include a trailing newline character and are not printed by libfido2 on stderr.

fido_assert_new(3), fido_cred_new(3), fido_dev_info_manifest(3), fido_dev_open(3)
May 25, 2018 Linux 5.3.12-arch1-1