less is a terminal pager program on Unix, Windows, and Unix-like systems used to view (but not change) the contents of a text file one screen at a time.

Mark Nudelman initially wrote less during 1983–85, in the need of a version of more able to do backward scrolling of the displayed text.

less can be invoked with options to change its behaviour, for example, the number of lines to display on the screen.

By default, less displays the contents of the file to the standard output (one screen at a time).

If the file name argument is omitted, it displays the contents from standard input (usually the output of another command through a pipe).