liblogger is a structured logger for C/C++. The output format is JSON. liblogger supports writing to stdout, stderr, and to a file.

To use this library, initialize the logger with s_log_init() and call the s_log macro. The latter macro takes a log level, any number of s_log_field_t pointers containing a string key and a log value.

The supported int values are: int, int8, int16, int32, int64 The supported uint values are: uint, uint8, uint16, uint32, uint64 And float, double, and string.

The supported log levels are: trace, debug, info, warn, error, fatal,

For a successful log entry to be made, a key and a value need to be provided. If no value is provided, that field will not be logged. Memory is freed after the log entry is written.

Build the example:

make example

#include <stdio.h>

#include "logger.h"

int
main(int argc, char **argv)
{
    s_log_init(stdout); 
    s_log(S_LOG_INFO, 
        s_log_string("msg", "records added successfully"),
        s_log_uint("count", 2));
    s_log(S_LOG_INFO, 
        s_log_string("msg", "records added successfully"),
        s_log_int64("count", 9223372036854775807));
    s_log(S_LOG_INFO, 
        s_log_string("msg", "record added successfully"),
        s_log_string("name", "Brian"),
        s_log_double("elapsed", 5.76));
    s_log(S_LOG_FATAL, s_log_string("msg", "dead :("));  
}

Expected output:

{ "timestamp": 1541620673, "level": "info", "msg": "records added successfully", "count": 2 }
{ "timestamp": 1541620673, "level": "info", "msg": "records added successfully", "count": 9223372036854775807 }
{ "timestamp": 1541620673, "level": "info", "msg": "records added partially", "count": 3 }
{ "timestamp": 1541620673, "level": "info", "msg": "record added successfully", "name": "Brian", "elapsed": 5.75 }

Write to a log file:

FILE *f = fopen("file.log", "w");
s_log_init(f);
s_log(S_LOG_INFO,
    s_log_string("msg", "records added successfully"),
    s_log_uint8("count", 2));
fclose(f);

• jansson

A lot of thanks to Ayan George for the help with getting this where it is.

Brian Downs @bdowns328

BSD 2 Clause License.