What is "clogger" and how do I use it?

Q: How can I display log messages in a format other than text?

The logger only supports text format for log messages. If you want to use another format, such as JSON or XML, you will need to write your own formatting function and call it within the logger function.

Q: How can I filter log messages based on tag or level?

The logger does not offer advanced filtering of log messages. You can only control the overall message level using the `log_level` variable in the configuration file. If you want to filter messages based on tag or level, you will need to write your own filtering function and call it within the logger function.

Q: How do I debug C-logger if there's a problem?

The C logger provides a `logger_debug` function that displays information about the library's internal state. You can call it at any time to check if the C logger is working correctly.

François

C Logger is a simple and efficient logging library for the C language . It allows you to write log messages to a file or to the console, with varying levels of detail and control. In this article, we'll see what features C Logger offers, how to install it, and how to use it in your C projects.

The features of clogger

C logger is a lightweight library, consisting of only 500 lines of source code. It is compatible with the C89 standard and is thread-safe. It offers two types of logging:

Console logging, which displays log messages in standard output or error output.
Logging to a file, which writes log messages to a text file, with automatic rotation based on file size.

c logger also allows customization of logging with a configuration file, in which you can define the message format, level of detail, log file name, maximum file size, etc.

How do I install Clogger?

To install C Logger, simply download the source code from the GitHub repository and compile it with your preferred C compiler. For example, with gcc:

$ git clone https://github.com/yksz/c-logger.git $ cd c-logger $ gcc -c -o logger.o logger.c $ ar rcs libclogger.a logger.o

This will create a static archive libclogger.a that you can link to your C program. You will also need to include the logger.h header file in your source files.

How do I use clogger?

To use C Logger, you must first initialize the library with the `logger_init` , passing it the name of the configuration file or `NULL` if you want to use the default settings. Then, you can use the `logger` to write log messages, passing it a tag, a level, and a message. For example:

#include "logger.h" int main(void) { /* Initialize the library with the config.ini file */ if (logger_init("config.ini") != 0) { fprintf(stderr, "Error initializing c logger\n"); return 1; } /* Write an INFO level message with the "main" tag */ logger("main", LOG_INFO, "Program started"); /* Write an ERROR level message with the "main" tag */ logger("main", LOG_ERROR, "Fatal error"); /* Terminate the library */ logger_end(); return 0; }

The format of log messages depends on the configuration file used. By default, it is in the form:

datetime tag level message

For example :

2023-06-13 02:37:16 main INFO Program start 2023-06-13 02:37:16 main ERROR Fatal error

The format can be modified using the following variables in the configuration file:

%d: the date in YYYY-MM-DD format
%t: the time in HH:MM:SS format
%c: the message tag
%l: the message level
%m: the message
%n: a line break

For example, if we want a shorter format, we can use:

[formats] simple = "%t %c %l %m%n"

What levels of detail are available?

c logger offers five levels of detail for log messages:

LOG_DEBUG: for debugging messages, useful for developers.
LOG_INFO: for informative messages, useful for users.
LOG_WARN: for warning messages, useful for reporting abnormal but not critical situations.
LOG_ERROR: for error messages, useful for signaling critical situations that prevent the program from functioning correctly.
LOG_FATAL: for fatal messages, useful for signaling irrecoverable situations that require stopping the program.

The level of detail in log messages can be controlled using the `log_level` in the configuration file. For example, if you only want to display ERROR and FATAL messages, you can use:

[general] log_level = 3

The levels are numbered from 0 to 4, from most detailed to least detailed. By default, the level is at 0, which displays all messages.

How to control the size of the log file?

c logger allows you to limit the log file size using the `max_file_size` in the configuration file. For example, if you want the log file to be no larger than 1 MB, you can use:

[general] max_file_size = 1048576

The size is expressed in bytes. By default, there is no size limit.

When the log file reaches its maximum size, c logger creates a new file with a numeric suffix. For example, if the log file name is log.txt , the first file created will be log.txt.1 , then log.txt.2 , and so on. The maximum number of files created is controlled by the max_file_count in the configuration file. For example, if you want to keep a maximum of 10 log files, you can use:

[general] max_file_count = 10

By default, there is no limit on the number of files.

FAQ

What is the difference between c logger and other logging libraries like log4c or nglogc?

C logger stands out for its simplicity and lightweight design. While it doesn't offer as many features as some more comprehensive libraries, it covers the essential needs of logging. It is also compatible with the C89 standard and thread-safe.

How can I display log messages in a format other than text?

c logger only supports text format for log messages. If you want to use another format, such as JSON or XML, you will need to write your own formatting function and call it within the logger .

How can I filter log messages based on tag or level?

c logger does not offer advanced filtering of log messages. You can only control the overall message level using the `log_level` in the configuration file. If you want to filter messages based on tag or level, you will need to write your own filtering function and call it within the `logger` .

How can I send log messages to a destination other than the console or a file?

The C logger only supports the console and files as destinations for log messages. If you want to send messages to another destination, such as a database or web service, you will need to write your own send function and call it within the logger .

How do I debug C-logger if there's a problem?

`logger_debug` function that displays information about the library's internal state. You can call it at any time to check if the C logger is working correctly.

Conclusion

clogger is a simple and efficient logging library for the C language. It allows you to write log messages to a file or to the console, with varying levels of detail and control. It is easy to install and use, and offers customization via a configuration file. clogger is based on object-oriented programming principles , which allows you to create logger objects with specific properties and methods. clogger is an ideal solution for developers who want to add logging functionality to their C projects without any hassle.