less, more, pg (UNIX/Linux command) (original) (raw)


music

| OSdata.com: programming text book | | OSdata.com | | ---------------------------------------------------------------------------------------------- | | ---------- |

summary

This subchapter looks at less, more, and pg, a related family of UNIX (and Linux) commands.

less, more, pg

This subchapter looks at less, more, and pg, a related family of UNIX (and Linux) commands.

less, more, and pg are utilities for reading a very large text file in small sections at a time.

pg is the name of the historical utility on BSD UNIX systems.

more is the name of the historical utility on System V UNIX systems.

pg and more are very similar and have almost the same functionality and are used in almost the exact same manner, except for whether you type pg or more.

less is a more modern version that has the capaibilites of more along with additional new capabilities.

Mac OS X has all three versions installed. It is common to find both more and less on Linux systems. The older versions are typically included so that old scripts written before the invention of less will still work.

The name less is a pun, from the expression “less is more.”

Try using less with your test file file01.txt.

You are going to try less first.

$ less file01.txt

If that doesn’t work, you are going to try more next.

$ more file01.txt

If that doesn’t work, you are going to try pg last.

$ pg file01.txt

One of the three will work. You can try the others to see if they are available on your system, but for the exercise, use the first one that works.

$ less file01.txt
This is a line of text in my first file.
This is another line. To be, or not to be: that is the question: 1234567890
ABC
XYZ
abc
xyz
$

Now we are going to see the real power of less with a long file.

$ less file02.txt
This is a line of text in my second file.
This is another line. To be, or not to be: that is the question:
Whether 'tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles,
And by opposing end them? To die: to sleep;
No more; and by a sleep to say we end
The heart-ache and the thousand natural shocks
That flesh is heir to, 'tis a consummation
Devoutly to be wish'd. To die, to sleep;
To sleep: perchance to dream: ay, there's the rub;
For in that sleep of death what dreams may come
When we have shuffled off this mortal coil,
Must give us pause: there's the respect
That makes calamity of so long life;
For who would bear the whips and scorns of time,
The oppressor's wrong, the proud man's contumely,
The pangs of despised love, the law's delay,
The insolence of office and the spurns
That patient merit of the unworthy takes,
When he himself might his quietus make
File02.txt

Notice that you are not yet back to the shell prompt. You are still in the less command. You are only one page into the file. less allows you to view long files one page at a time, instead of scrolling them off the top of your screen.

Type the SPACE key to see another page of text.

That patient merit of the unworthy takes,
When he himself might his quietus make
With a bare bodkin? who would fardels bear,
To grunt and sweat under a weary life,
But that the dread of something after death,
The undiscover'd country from whose bourn
No traveller returns, puzzles the will
And makes us rather bear those ills we have
Than fly to others that we know not of?
Thus conscience does make cowards of us all;
And thus the native hue of resolution
Is sicklied o'er with the pale cast of thought,
And enterprises of great pith and moment
With this regard their currents turn awry,
And lose the name of action. - Soft you now!
The fair Ophelia! Nymph, in thy orisons
Be all my sins remember'd. 1234567890
ABC
XYZ
abc
xyz
(END)

Notice that you are not yet back to the shell prompt. Even though the entire file contents have been listed, you are still in the less command.

Typing lower case q will quit the less (or more or pg) program.

less (and the other two utility commands) displays one page at a time. This is in contrast with cat, which displays the entire file at once.

other

On November 8, 2010, Ramesh Natarajan named this the number 43 most frequently used UNIX/Linux command at this web page 50 Most Frequently Used UNIX / Linux Commands (With Examples).

comments, suggestions, corrections, criticisms

free music player coding example

Coding example: I am making heavily documented and explained open source code for a method to play music for free — almost any song, no subscription fees, no download costs, no advertisements, all completely legal. This is done by building a front-end to YouTube (which checks the copyright permissions for you).

View music player in action: www.musicinpublic.com/.

Create your own copy from the original source code/ (presented for learning programming).

Because I no longer have the computer and software to make PDFs, the book is available as an HTML file, which you can convert into a PDF.

†UNIX used as a generic term unless specifically used as a trademark (such as in the phrase “UNIX certified”). UNIX is a registered trademark in the United States and other countries, licensed exclusively through X/Open Company Ltd.