Text and editors

Not running Starting usually ~20 s

Step 1 of 8 · on a machine · 4 min

No errors?

Read the start, the end and the new lines of a log without paging through the whole file.
Find and count lines with grep without taking empty output to mean "nothing there".
Edit a file in Vim and check what reached the disk outside the editor.

The report service restarted twice overnight. The on-call engineer checked its log and wrote: "No errors, grep error found nothing."

Exercise · look

In ~/text-lab, run the two commands below: the on-call engineer's search and a look at the last five lines of the log.

Check yourself 1 question

Why did grep error find nothing, even though the log has an error?

grep checks every line to the end of the file: grep listening service.log finds lines both at the start of the log and at the end.
Nothing writes to this log any more, and tail has already shown the error in it: grep reads the same whole file.
Without read access grep would print Permission denied. The file is yours — check ls -l service.log.

The log says ERROR in capitals, and the on-call engineer searched for error in lowercase.

Ubuntu 24.04