SD_INFO, SD_DEBUG - APIs for new-style daemons


   #include <systemd/sd-daemon.h>

   pkg-config --cflags --libs libsystemd


   sd-daemon.h provides APIs for new-style daemons, as implemented by the
   systemd(1) service manager.

   See sd_listen_fds(3), sd_notify(3), sd_booted(3), sd_is_fifo(3),
   sd_watchdog_enabled(3) for more information about the functions
   implemented. In addition to these functions, a couple of logging
   prefixes are defined as macros:

       #define SD_EMERG   "<0>"  /* system is unusable */
       #define SD_ALERT   "<1>"  /* action must be taken immediately */
       #define SD_CRIT    "<2>"  /* critical conditions */
       #define SD_ERR     "<3>"  /* error conditions */
       #define SD_WARNING "<4>"  /* warning conditions */
       #define SD_NOTICE  "<5>"  /* normal but significant condition */
       #define SD_INFO    "<6>"  /* informational */
       #define SD_DEBUG   "<7>"  /* debug-level messages */

   These prefixes are intended to be used in conjunction with stderr-based
   logging as implemented by systemd. If a systemd service definition file
   is configured with StandardError=journal, StandardError=syslog or
   StandardError=kmsg, these prefixes can be used to encode a log level in
   lines printed. This is similar to the kernel printk()-style logging.
   See klogctl(2) for more information.

   The log levels are identical to syslog(3)'s log level system. To use
   these prefixes simply prefix every line with one of these strings. A
   line that is not prefixed will be logged at the default log level

   Example 1. Hello World

   A daemon may log with the log level NOTICE by issuing this call:

       fprintf(stderr, SD_NOTICE "Hello World!\n");


   These APIs are implemented as a shared library, which can be compiled
   and linked to with the libsystemd pkg-config(1) file.


   systemd(1), sd_listen_fds(3), sd_notify(3), sd_booted(3),
   sd_is_fifo(3), sd_watchdog_enabled(3), daemon(7), systemd.service(5),
   systemd.socket(5), fprintf(3), pkg-config(1)


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.