log.c

A simple logging library implemented in C99

Usage

You can include the code below in your cmake project and #include <log.h> in your sources.

FetchContent_Declare(log # Recommendation: Stick close to the original name.
                     GIT_REPOSITORY https://github.com/innerout/log.c.git)
FetchContent_GetProperties(log)
if(NOT log_POPULATED)
  FetchContent_Populate(log)
  add_subdirectory(${log_SOURCE_DIR} ${log_BINARY_DIR})
  FetchContent_MakeAvailable(log)
endif()
target_link_libraries(YOUR_LIB_NAME log)

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

log_set_quiet(bool enable)

Quiet-mode can be enabled by passing true 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 files and callbacks if any are set.

log_set_level(int level)

The current logging level can be set by using the log_set_level() function. All logs below the given level will not be written to stderr. By default the level is LOG_TRACE, such that nothing is ignored.

log_add_fp(FILE *fp, int level)

One or more file pointers where the log will be written can be provided to the library by using the log_add_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

Any messages below the given level are ignored. If the library failed to add a file pointer a value less-than-zero is returned.

log_add_callback(log_LogFn fn, void *udata, int level)

One or more callback functions which are called with the log data can be provided to the library by using the log_add_callback() function. A callback function is passed a log_Event structure containing the line number, filename, fmt string, va printf va_list, level and the given udata.

log_set_lock(log_LockFn fn, void *udata)

If the log will be written to from multiple threads a lock function can be set. The function is passed the boolean true if the lock should be acquired or false if the lock should be released and the given udata value.

const char* log_level_string(int level)

Returns the name of the given log level as a string.

LOG_USE_COLOR

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

DISABLE_LOGGING

If the library is compiled with -DDISABLE_LOGGING all the calls to log_* functions are replaced with ;.

License

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