log.c2

A simple logging library.

Log.c2 is based on rxi/log.c with MIT LICENSE which is inactive now. Log.c has a very flexible and scalable architecture. There are some enhancements added in log.c2.

Enhancements:

• Print logs to stdout/stderr.
• Backup log file by file line number.
• Add more log levels.
• Enhance time accuracy.
• ...

Usage

log.c and log.h should be dropped into an existing project and compiled along with it. The library provides function-like macros for logging:

log_debug(const char *fmt, ...);
log_info(const char *fmt, ...);
log_notice(const char *fmt, ...);
log_warn(const char *fmt, ...);
log_error(const char *fmt, ...);
log_critical(const char *fmt, ...);
log_alert(const char *fmt, ...);
log_emergency(const char *fmt, ...);

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

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

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

2020-08-11_16:05:03_877 [EMERGE] [demo_stdout.c:5  ]: this is a log.

log_stdout_verbose(int level)

Print log to stdout. Any messages above the given level are ignored.

log_stderr_verbose(int level)

Print log to stderr. Any messages above the given level are 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:

2020-08-11_16:05:03_877 [EMERGE] [demo_stdout.c:5  ]: this is a log.

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

log_add_file_backup(char *filename, size_t n, int level)

File where the log will be written can be backuped by file line number. The backup will be renamed with a timestamp tail. A new file will be opened to continue logging.

demo.log  demo.log_2021-08-10_16:31:18_857

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.

Help

There are demos in demo/.

❯ make
❯ ./demo
===========================================================
  Usages: demo [demoname]
Demoname: stdout
Demoname: file
Demoname: file_backup
❯ ./demo stdout
...

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.