I carry a Garmin Etrex 10 when I go bug-collecting. It's a handheld GPS receiver without many frills, and I only use it to record the latitude and longitude of each of my collecting sites as a waypoint. At the start of a field trip I delete all previous waypoints. When I do this, the trip's…

I've written several BASH scripts that use GNU AWK's printf function to round off decimal numbers. Now I've learned that the rounding is biased, and I need to re-do the scripts. For me the desirable way to round off a decimal is to round up if the bit to be discarded is greater than one half, and…

Recently I was checking for unmatched braces in a big text file with nearly half a million lines (300+ MB). Was there a closing brace for every opening brace? The text file was called 'beetle' and was actually a tab-separated table with each line divided into 77 fields. What I wanted to do was find…

Flags in AWK are variables which are set to either true or false. They're handy for defining ranges over which AWK can act, as shown below. The AWK used here is GNU AWK 4.1.1 (gawk 4). Sometimes flags aren't needed I'll demonstrate with a simple text file called demo, which has 6 lines with 3…

Lexical illusions are very hard to find when proofreading. The most common lexical illusion is a duplicated word, as in this well-known example: A lexical illusion: many people are not aware that the the brain will automatically ignore a second instance of the word 'the' when it starts a new line. …

Swapping the rows and columns in a table on the command line would seem to be a fairly easy thing to do. For example, with this tab-separated table (called 'tabbed') as input: get this tab-separated table ('swapped') as output: Datamash Transposing rows and columns is indeed easy if you have the…

Backreferences are part of the complicated and sometimes confusing world of regular expressions. The basic idea is this: you can substitute any part of a regular expression with a backslash followed by a number, so long as you surround the part to be substituted with round brackets. The command…

Most people store and organise their personal emails as individual files (messages) in folders. Those folders might be on a webmail company's servers, or in a mail client program on the user's personal computer. In both cases the emails are probably in a special email format. I'm horribly…

I recently scripted a GUI dialog that lists my 10 most recently modified files in reverse chronological order and allows me to choose more than 1 file for opening. The dialog is launched with a keyboard shortcut and is shown here with 2 files selected: The script is in copy-and-paste form at the…

My wife likes to organise and store information in Gnumeric spreadsheets. Every now and then she needs to filter her data and save the result to a new spreadsheet. Gnumeric doesn't have a simple way to do that. It has a complicated way to do it ('Advanced Filter'), but nothing so straightforward as…