libssh2_trace_sethandler - Man Page
set a trace output handler
#include <libssh2.h> typedef void (*libssh2_trace_handler_func)(LIBSSH2_SESSION *session, void* context, const char *data, size_t length); int libssh2_trace_sethandler(LIBSSH2_SESSION *session, void* context, libssh2_trace_handler_func callback);
libssh2_trace_sethandler installs a trace output handler for your application. By default, when tracing has been switched on via a call to libssh2_trace(), all output is written to stderr. By calling this method and passing a function pointer that matches the libssh2_trace_handler_func prototype, libssh2 will call back as it generates trace output. This can be used to capture the trace output and put it into a log file or diagnostic window. This function has no effect unless libssh2 was built to support this option, and a typical "release build" might not.
context can be used to pass arbitrary user defined data back into the callback when invoked.
Added in libssh2 version 1.2.3
15 Jan 2010 libssh2 1.2.3 libssh2 manual