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Basic logger for C and C++ projects
C C++
Latest commit b8f4a52 @ntpeters Update


NOTE: This project was made primarily as a learning exercise, and will neither be maintained nor should be used in a production environment. (See Caveats for more info)

A basic, easy to use logger for output of messages at various logging levels with date/time stamp to standard out and a defined log file.

Example Screenshot


  • Time/date stamped output
  • Console output is colored according to the level of the log message
  • Error levels automatically print errno if it has been set
  • Variable length argument list
  • Supports writing of stacktraces. Stacktraces are "prettyfied" to give the user an easiear to read trace
  • Has an option to wrap messages over 80 characters to multiple lines
  • Written in C, for use in C and C++ projects


  • Not thread safe
  • Not signal safe
  • Currently does not have millisecond granularity in timestamp

Building with SimpleLogger

First be sure to compile libsimplog.a:


This will run CMake in a build subdirectory, and execute the generated makefile(s) there. The resultant libsimplog.a will then be copied to the root SimpleLogger directory.

When building your project, you need to add the SimpleLogger directory in your build path:

-I <path-to-SimpleLogger-dir>

You also need to link against libsimplog.a:

-L <path-to-SimpleLogger-dir> -lsimplog

Finally, just include simplog.h in your project files:

#include <simplog.h>

You're all set! Check out the Usage section below for how to use SimpleLogger in your program.


Each message must be accompanied by a level. Supported levels are:

SIMPLOG_FATAL   = -2 : A fatal error has occured, the program will exit immediately
SIMPLOG_ERROR   = -1 : An error has occured, the program may not exit
SIMPLOG_INFO    = 0  : Nessessary information regarding program operation
SIMPLOG_WARN    = 1  : Any circumstance that may not affect normal operation
SIMPLOG_DEBUG   = 2  : Standard debug messages
SIMPLOG_VERBOSE = 3  : All debug messages

Here is an example of how to create a log entry:

simplog.writeLog( <desired_level>, "Message", <var-args> );

For example, to recreate part of the output in the screenshot above:

simplog.writeLog( SIMPLOG_FATAL, "Test Fatal" );
simplog.writeLog( SIMPLOG_ERROR, "Test Error" );
simplog.writeLog( SIMPLOG_INFO, "Test Info" );
simplog.writeLog( SIMPLOG_WARN, "Test Warn" );
simplog.writeLog( SIMPLOG_DEBUG, "Test Debug" );
simplog.writeLog( SIMPLOG_VERBOSE, "Test Verbose" );

To write a stacktrace, just call:


Stacktraces will automatically "prettyfied" to provide easier to read traces.

NOTE: Pretty stacktraces are currently broken on MacOS, and will fallback to standard backtrace output.

If you want to load a config file to setup the logger:

simplog.loadConfig( <desired-config-file> );

With a config that can use any of the following options:

silent=<true-or-false>    // Sets the silent mode
wrap=<true-or-false>      // Sets if too long lines are wrapped
flush=<true-or-false>     // If the log file should be flushed or not
debug=<0-to-3>            // Set the debug level, 0 - 3
logfile=<logfile-path>    // Set the path to the logfile to output to

There are individual functions to set each of these parameters manually as well. See the documentation below.



    Writes output to defined logfile and standard out/err with
    date/time stamp and associated log level.

    Can take formatted string like printf, with a variable sized list of

    Prints errno when appropriate.

    Always adds new line to output.

    Logging Levels:
    -2 : Fatal          - A fatal error has occured: program will exit immediately
    -1 : Error          - An error has occured: program may not exit
    0  : Info           - Nessessary information regarding program operation
    1  : Warnings       - Any circumstance that may not affect normal operation
    2  : Debug          - Standard debug messages (default)
    3  : Debug-Verbose  - All debug messages

    int loglvl      - The desired output logging level.  See above table for levels
    const char* str - The message to be output. This is a format string
    ...             - Variable length list of arguments to be used with the format string (optional)
void writeLog( int loglvl, const char* str, ... );


    Prints the stacktrace to logs for the current location in the program.
    Most recent calls appear first.

    Set to a max of 15 lines of the stacktrace for output.
void writeStackTrace();


    Loads logger configuration settings from the given config file.

    Supported settings are:

    silent  - Enables/disables silent mode (see setLogSilentMode)
    wrap    - Enables/disables line wrapping (see setLineWrap)
    flush   - Determines if the log file should be cleared (see flushLog)
    debug   - Sets the debug level (see setLogDebugLevel)
    logfile - Sets the path to the log file (see setLogFile)

    const char* config - Logger config file to parse and load settings from

void loadConfig( const char* config );


    Sets the desired debug level for writing logs.

    Debug Levels:
    0  : Info           - Nessessary information regarding program operation
    1  : Warnings       - Any circumstance that may not affect normal operation
    2  : Debug          - Standard debug messages (default)
    3  : Debug-Verbose  - All debug messages

    int level - desired debug level
void setLogDebugLevel( int level );


    Sets the filename for log output.

    const char* file - desired log output file
void setLogFile( const char* file );


    Enables/Disables silent mode.
    When silent mode is enabled, no output will be written to standard out.
    Log output will continue normally.

    bool silent - Desired state of silent mode: false = Disabled (default), true = Enabled
void setLogSilentMode( bool silent );


    Enables/Disables line wrapping.
    When line wrapping is enabled, lines that are over 80 characters will be 
    wrapped multiple times so that each line is below 80 characters.

    bool wrap - Desired state of line wrapping: true = Enabled (default), false = Disabled
void setLineWrap( bool wrap );


    Flushes the contents of the logfile by deleting it and recreating
    a new empty logfile of the same name.
void flushLog();

Frequently Asked Questions

Q: There are already a ton of loggers out there. Why make another one?

A: The main idea behind this project was a learning experience in C while making something somewhat useful. I just wanted to make a logger that is simple and easy to use, and has output that is relatively pleasant to look at.

Q: Why don't you have feature X or Y?

A: As I said, the goal was to create a simple and easy to use logger. As such, there are probably some features this logger doesn't have when compared to some more feature rich alternatives.

Q: You did something stupid/improper in your code.

A: If there is something dumb or not proper that I did, please open an issue and let me know! Since this was largely a learning project I would love to hear about anything bad I've done here!

Q: I found a bug / I'm having problems

A: If you either found a bug or are having problems with this logger, please open an issue describing your dilema and I'll take a look!


If you like SimpleLogger, then please star it on GitHub and share it with others!

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