sort, cut, awk and sed.
WHAT sort DOES
Orders lines.
WHAT THE USEFUL OPTIONS ARE
Numeric ordering Reverse Unique By a specific field
WHY NUMERIC MATTERS
Without it, ten sorts before two.
WHAT uniq DOES
Collapses adjacent duplicate lines, optionally counting them.
WHY IT MUST FOLLOW sort
It only compares neighbours.
WHAT THE COUNTING COMBINATION ACHIEVES
A frequency list, which answers most log questions.
WHAT cut DOES
Extracts fields by delimiter or position.
WHAT awk DOES
Processes lines as fields, with logic.
WHAT ITS SIMPLEST USE IS
Printing a chosen column.
WHY THAT ALONE JUSTIFIES LEARNING IT
Most log analysis is selecting one column and counting it.
WHAT sed DOES
Edits a stream, most often substituting text.
WHAT THE SUBSTITUTION FORM IS
s, then the pattern, the replacement, and flags, separated by slashes.
WHAT THE IN-PLACE OPTION DOES
Modifies the file directly.
WHY THAT DESERVES CAUTION
There is no undo, and a wrong pattern can corrupt every matched file.
WHAT TO DO FIRST
Run it without the in-place option and read the output.
WHAT TO ALWAYS KEEP
A backup, which the in-place option can create for you.
