Using log files

Log files provide a way to track exactly what is going on in a Python plugin or script, by creating messages that are available even if the script or QGIS crashes. These log messages make troubleshooting easier. In this recipe, we'll demonstrate two methods used for logging. One method is using actual log files on the filesystem, and the other is using the QGIS Log Messages window, which is available by clicking on the yellow triangle with an exclamation point at the bottom-right corner of the QGIS application window, or by selecting View menu, then clicking on Panels, and then checking Log Messages.

Getting ready

To use log files, we must configure the QGIS_LOG_FILE environment variable by performing the following steps so that QGIS knows where to write log messages:

1. From the QGIS Settings menu, select Options.
2. In the Options dialog, select System panel.
3. In the System panel, scroll down to the Environment section.
4. In the Environment section, check the Use custom variables...