Logging library for C

A lightweight logging library for C projects, supporting multiple log levels and output to stdout or file, built in pure C and CMake

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How to use

loggy is built using pure C and CMake, so it does not require any other dependencies. All you need is in the list below:

• CMake (starting with 3.16)
• gcc or clang (c11)

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How to build

Follow the steps below to build loggy

# build shared (so/dll) library
cmake -B build -DBUILD_SHARED_LIB=ON
cd build
# install library into the system
make install

Note: sometimes you need to run make install as sudo.

Now you can use loggy. Here is CMake instructions you need to use loggy

find_package(loggy REQUIRED)

target_link_libraries(YOUR_PROGRAM
    PUBLIC
        loggy
)

Cannot open shared object file on Linux

If you get a message: error while loading shared libraries: libloggy.so: cannot open shared object file: No such file or directory, you need to run the following commands:

echo "/usr/local/lib64" | sudo tee /etc/ld.so.conf.d/loggy.conf
sudo ldconfig

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API reference

You can use direct or mediaded logging. Direct logging allows you specify what type of logging you want to use (the list below), message you want to see in the log, log source file and line. Instead of that you can use mediaded (e.g. simplified) functions.

Log flags

There are a several log flags you can use to configure your logs

#define LOG_NONE        (0)         // No date and time
#define LOG_DATE        (1 << 0)    // Add date dd/mm/yy
#define LOG_TIME        (1 << 1)    // Add time hh/mm/ss
#define LOG_COLORIZED   (1 << 2)    // Add ANSI colors for levels

// Shortcuts
#define LOG_DEFAULT     (LOG_TIME)  // Add time
#define LOG_FULL        (LOG_TIME | LOG_DATE) // Add date and time

Using thems, you can specify information you want to log. As you can see, log type and message are still required

Do not use LOG_COLORIZED flag if you want to log into devices that do not support ANSI colors (i.e. files). Otherwise you will get message with escape-sequence as chars

Log types

The log type you need to specify to make a log note. There is no point to describe every type, I hope these names are clear enough

typedef enum {
    FATAL   = 0,
    ERROR   = 1,
    INFO    = 2,
    WARNING = 3,
    DEBUG   = 4,
} log_level_t;

Functions

int8_t log_init(
    log_level_t level, 
    uint8_t flags
)

Init log module and set default log level and flags. Return 0 on success or if the module is initialized. Return -1 if wrong log level data was given.

void log_set_level(log_level_t level)

Set log level, see "Log types" section for details

void log_set_flags(uint8_t flags)

Set log flags, see "Log flags" section above for details

int8_t log_add_stdout_sink()

Call it, if you need to log into stdout

int8_t log_add_file_sink(const char *path)

int8_t log_add_custom_sink(
    log_printer printer,
    log_closer closer,
    void *ctx
)

Add a custom sink (UART or something else).

You can log_add_file_sink if you need add one more log file. It requires the file path.

void log_debug(message)

void log_info(message)

void log_warning(message)

void log_error(message)

void log_fatal(message)

Here is a bunch of functions for simplified logging. There is no need to describe every function separately because of the names. Every function accepts message and displays it in all log files initialized before

Note: actually, these functions are macros. So you do not have to worry about stack usage. It is just the interface of logger_ function

void log_exit()

The function for deinitialization of all log files. It closes files and deallocates file descriptors. This function is optional since it is set as atexit in the initialization function log_init.

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