What is a pager?

I saw "pager" in several places:

less is a terminal pager program on Unix

option -P for man Specify which output pager to use.

What is a pager? How is it related to and different from a terminal? Thanks.

Asked By: Tim

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As the name implies, roughly a pager is a piece of software that helps the user get the output one page at a time, by getting the size of rows of the terminal and displaying that many lines.

The most popular pagers in a UNIX text environment are more and less.
The latter is kind of a joke as less can actually do more then more.

Answered By: schaiba

I would like to confirm the comments of @schaiba and @Faheem Mitha.

@schaiba :

if you don’t pipe your output through a pager (less, more and most
come to mind), that output will appear on your screen all at once and
thus you might lose something if said output is bigger than the number
of lines of your terminal.

@Faheem Mitha:

Scroll back is also finite. A pager is not limited to any particular
size.


You can try easily by changing the terminal environment variables setttings

First, try man bash (You need a command manpage that’s long enough. Google told me man bash is longest one) with default pager. (I don’t know which it’s the default one but whatever it definitely has one).

Then set PAGER to empty. (Need to export or it won’t be written into terminal environment variables)

PAGER=
export PAGER

Again, try man bash. You will find that even if you sroll up, you can’t see the beginning of the man bash page.

So now you(I) understand how pagers matter.

Answered By: Rick

In the original(?) Motif (and LessTif), the "pager" provided for many (9,16) screens to exist simultaneously- a little map in one corner of a screen, the "pager" enabled one to choose any one of these for display at a time – a wonderful feature that seems to have been lost. Why? I have used LessTif for many years for this feature (9 screens), but graphics no longer work through LessTif ??? 🙁

Evolution is not always for the better.

Answered By: John Beck
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