= nng_log_set_logger(3) // // Copyright 2024 Staysail Systems, Inc. // // This document is supplied under the terms of the MIT License, a // copy of which should be located in the distribution where this // file was obtained (LICENSE.txt). A copy of the license may also be // found online at https://opensource.org/licenses/MIT. // == NAME nng_log_set_logger - set logging handler == SYNOPSIS [source, c] ---- #include typedef void (*nng_logger)(nng_log_level level, nng_log_facility facility, const char *msgid, const char *msg); void nng_null_logger(nng_log_level, nng_log_facility, const char *, const char *); void nng_stderr_logger(nng_log_level, nng_log_facility, const char *, const char *); void nng_system_logger(nng_log_level, nng_log_facility, const char *, const char *); void nng_log_set_logger(nng_logger logger); ---- == DESCRIPTION The `nng_log_set_logger` is used to set the base logging function to _logger_. The _logger_ may be a user defined function to process log messages. Only a single logger may be registered at a time. If needed, the logger should make copies of either _msgid_ or _msg_, as those may not be valid once the logger function returns. The `nng_null_logger` function is an implementation of `nng_logger` that simply discards the content. This is the default logger, so logging is disabled by default. The `nng_stderr_logger` function is an implementation that logs messages to the standard error stream. It will attempt to colorize messages by the severity, if the standard error is a terminal device. This can be supressed by setting either the `NO_COLOR` or `NNG_LOG_NO_COLOR` environment variables. The `nng_system_logger` attempts to use an appropriate system facility to log messages. For POSIX systems, this means using `syslog` to process the messages. For other the `nng_stderr_log` may be used as a fallback. == SEE ALSO xref:nng_log_set_facility.3.adoc[nng_log_set_facility(3)], xref:nng_log_set_level.3.adoc[nng_log_set_level(3)], xref:nng_log.3.adoc[nng_log(3)]