vLogger

vLogger is a simple C log implementation library which aims to be fast and safe.

Install

vLogger has currently been tested on GNU/Linux and macOS only.

Run make && make install to compile and install the components using the default directory prefix (/usr/local).

Alternatively, run make && make install -e PREFIX=/custom/path to install the components with a custom directory prefix. If the path is relative to your user's home directory, it's best to use -e PREFIX=$HOME/some/path.

The static library will be installed into $PREFIX/lib/libvlogger.a and the header file into $PREFIX/include/vlogger.h.

When compiling your own programs, use the -I $PREFIX/include and -L $PREFIX/lib GCC compiler options and -lvlogger options within your Makefiles or directly into the command line.

Usage

#include <vlogger.h>
#include <stdlib.h>

int main(int argc, char const *argv[]) {
  char *logFilePath = NULL;
  if (argc == 2) {
    logFilePath = (char *)argv[1];
  }

  // Initialise vLogger here...
  if (!vLogInit(LOG_INFO, logFilePath)) {
    fprintf(stderr, "Unable to initialise the log engine: %s\n", strerror(errno));
    return EXIT_FAILURE;
  }

  // The rest of your code here...

  Info("This is an info message with no arguments");
  Warn("This is a warning message regarding %s", someVariable);

  WarnIf((otherVar < 42), "Something strange happened to 'otherVar' %d", otherVar);

  // This will stop the program and return errno or EXIT_FAILURE
  Fatal("An unrecoverable error happened");

  return EXIT_SUCCESS;
}

See also the examples directory for more examples.

Date format

vLogger uses the ISO 8601 date format (local date/time with UTC offset). The output format of an event is:

YYYY-MM-DDTHH:MM:SS+ZZZZ | <PID> | <ThreadID> | <LEVEL> | <Your Message>

For example:

2022-04-07T16:09:33+0100 | 1234  | 5678910111 | INFO    | This thing happened

Thread and Signal safety

vLogger writes the message to the log stream using the AS-Safe (async-safe) write() system call. The other intermediate functions are all MT-Safe (thread-safe):

• localtime_r(): MT-Safe
• strftime(): MT-Safe as long as no other threads call setlocale() while this function is executing
• snprintf(): MT-Safe as long as the buffer is not shared with other threads
• strlen(): MT-Safe
• time(): MT-Safe
• getpid(): MT-Safe and AS-Safe
• pthread_self(): MT-Safe and AS-Safe

Run the tests

Run make tests.

Play with the examples

Run make examples, you will find each example compiled under bin/examples/.

License

vLogger is licensed under LGPL. Please refer to the LICENSE file for detailed information.