Glog

Glog, short for Google logging, is a C++ logging library developed by Google. It provides multi-level, configurable logging for C++ programs and is widely used in both Google code and open-source projects. The library defines logging macros such as LOG(INFO), LOG(WARNING), LOG(ERROR), and LOG(FATAL) for standard messages, as well as VLOG(n) for verbose logging. A FATAL log prints the message and terminates the program, while INFO and WARNING messages are written to logs or standard error depending on configuration.

Initialization is done with google::InitGoogleLogging(argv[0]); and the behavior is controlled at runtime through a set of command-line flags (often used in conjunction with the gflags library) to determine output destinations and verbosity. Common flags include --logtostderr to write logs to standard error, --log_dir to specify a log file directory, --minloglevel to set the minimum severity, and --vmodule to adjust verbose levels per module. Globs of the library also support failure signal handlers and log rotation in its log files.

Glog is cross-platform and designed for integration into larger C++ projects. It is distributed as open-source software and is hosted on platforms such as GitHub under the google/glog repository. The project is released under a permissive license, making it suitable for use in a range of open-source and proprietary environments.

In typical usage, glog complements other Google-style tooling, such as gflags for command-line flags, and is employed to provide structured, severity-based logging that aids debugging and monitoring in complex C++ applications.