A simple logging library implemented in C99

Either log.c and log.h can be dropped into an existing project and compiled along with it or the Makefile can be executed to build liblog.so as a shared library if this repository is used as a package. The library provides 6 function-like macros for logging:

log_trace(const char *fmt, ...);
log_debug(const char *fmt, ...);
log_info(const char *fmt, ...);
log_warn(const char *fmt, ...);
log_error(const char *fmt, ...);
log_fatal(const char *fmt, ...);

Each function takes a printf format string followed by additional arguments:

log_trace("Hello %s", "world")

Resulting in a line with the given format printed to stderr:

20:18:26 TRACE src/main.c:11: Hello world

Quiet-mode can be enabled by passing 1 to the log_set_quiet() function. While this mode is enabled the library will not output anything to stderr, but will continue to write to the file if one is set.

The current logging level can be set by using the log_set_level() function. All logs below the given level will be ignored. By default the level is LOG_TRACE, such that nothing is ignored.

A file pointer where the log should be written can be provided to the library by using the log_set_fp() function. The data written to the file output is of the following format:

2047-03-11 20:18:26 TRACE src/main.c:11: Hello world

If the log will be written to from multiple threads a lock function can be set. The function is passed a udata value (set by log_set_udata()) and the integer 1 if the lock should be acquired or 0 if the lock should be released.

If the library is compiled with -DLOG_USE_COLOR ANSI color escape codes will be used when printing.

This library is free software; you can redistribute it and/or modify it under the terms of the MIT license. See LICENSE for details.