EINVAL: Valid solutions for invalid problems

less can do more

less is probably one of the most used programs in the UNIX world. It’s so ubiquitous we usually barely notice it. For clarity, I mean this less, not this one. Despite its ubiquity, very few people actually take time to learn its less obvious but still very useful features. Let’s change that!

First of all, the & key. It prompts for a search pattern and then acts like a filter, showing only the matching lines, not unlike grep. Unlike grep though, you can change this filter without closing less and it’s generally very useful if you need to filter the content as an afterthought, if you decide you really could use a filter only after producing copious amounts of output.

Another useful thing is toggling the commandline -options in a running less, once again without restarting it. For example you can press -S to toggle wrapping the long lines or -J to mark the lines matching the search pattern with an asterisk. It’s worth to keep in mind that every commandline option can be toggled this way, though obviously some are more useful this way than the others.

Last but not least, the marks known from Vim (among the others). By pressing m followed by almost any other key, you can save the current position in a text and then return to it by pressing ' followed by the same key. For instance you can save two distant places in a file with ma and mb and then cross-reference them by jumping between them with 'a and 'b. Considering less is very often used for reading lenghty manpages with lots of “See SOME OTHER SECTION for details”, it’s a godsend.

In general, every user of UNIX-like systems should at least skim the less keybindings, as even in such a simple tool there is much to learn. Press h to display them and have a good time reading through them! I know I had!

Part Two