Less: утилита постраничного просмотра файлов

Terminal pager

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. It is similar to , but has the extended capability of allowing both forward and backward navigation through the file. Unlike most Unix text editors/viewers, does not need to read the entire file before starting, allowing for immediate viewing regardless of file size.

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. The name came from the joke of doing "backwards more." Originally, less was developed for Unix, but it has been ported to a number of other operating systems, including MS DOS, Microsoft Windows, OS/2, and OS 9, as well as Unix like systems such as Linux. It is still maintained today by Nudelman. To help remember the difference between less and more, a common joke is to say, "," implying that less has greater functionality than A similar saying is that "less is more, more or less".

g: Highlight just the current match of any searched string. i: Search case insensitively. m: Show more detailed prompt, including file position. N: Show line numbers (useful for viewing source code). x3: Set tabstops (the number of columns per hard tab character) to the specified number (3, in this example) (useful for viewing source code). S: Disable line wrapping ("chop long lines"). Long lines can be seen by side scrolling. X: Leave file contents on screen when less exits. ? : Show help. follow name: Follow mode, for log files that get replaced while being viewed.

Key Command Next Page Next half Page Previous Page Previous half Page Edit Content or Next Line Previous Line Top of file End of file Follow Mode (for expanding logs or pipes). Interrupt (or from v581 ) to abort. or First Line or Last Line Line Forward Search for Text is interpreted as a regex. Backward Search like grep like filter Next Search Match Previous Search Match Turn off Match Highlighting (see g command line option) Toggle option , e. g., toggles option to match case in searches Set Mark Go to Mark or File information Next file Previous file Help. This is presented with less, to quit. Quit

The buffers=n and auto buffers options control how much memory less may use to buffer inputs. This is most relevant when less is directly accessing a named file that is modified or deleted while less is still running, and when less is receiving data from a pipe and the data can not be randomly accessed or regenerated. On the other hand, unlimited buffering means that less will request as much memory as it is fed data, which could drive the system into using virtual memory and swapping a lot of data between RAM and disks (dramatically slowing system performance for most applications on the host), or even further into memory exhaustion where any application on the host requesting memory may have that request denied, or may crash when attempting to access memory that the OS promised but can't find when the application actually attempts to use it and a page fault occurs. For this reason, some companies/organisations insist that less be used only with fixed buffering or not at all on production machines.