err - Describe error codes
err [ number ]
When an error occurs, a brief message is usually displayed describing the problem. However, some programs will just report an error code number. You can find out what an error code means by invoking the err shell script followed by a code number.
If you want to see the entire list of error codes and their descriptions, enter err without arguments.
Error reports with code numbers are usually accompanied by a line number reference (e.g. “Error #10 at 170”). Supply only the error code (e.g. “10”) but not the line number.