How can errors be extracted only from a log file?

To extract only errors from a log file, text filtering commands are usually used, such as grep in Linux. Suppose the errors in the log contain the word "ERROR" or "Error". Then you can run the command:

grep -i "error" /path/to/logfile.log

The -i option makes the search case-insensitive. If the log format is more complex, regular expressions can be used for precise searching of error lines.

You can also use log analysis tools, such as awk or sed, if more complex extraction is needed.