Shell Scripting Tutorial-15: Get Help; View Fancy Text & Reduce File Size Video Lecture | Shell Scripting: Discovering to Automate Command-Line Tasks - Back-End Programming

hello guys my name is mother and welcome
to my channel this is the 15th tutorial
in the series of tutorials on shell
programming in this tutorial we're gonna
check out three important commands the
first one is the man command now I have
my terminal opened up and what if I
forget about a command what if I forget
how to use a command what if I wish to
know more about a command what if I have
forgotten the options that come along
with the command man is basically the
help repository of UNIX that you can
access in such cases if suppose I wish
to know about the cat command then I can
simply type in man space cat my terminal
and press the Enter key and there you go
you see that the dollar prompt has been
suspended and the man page of cat
command opens up and you have the name
here and description and also the
synopsis
now you can here find all the options
that come with the cat command as you
can see we've discussed very few and you
can also find examples here and then you
can see the names of people who have
contributed in making the man page and
you can find all sorts of other
information so the man command is
basically what you used to see manuals
that come along with commands each and
every UNIX command has its own man page
and all the man pages are corrected in a
directory in the file system so that's
it about man and if you want to return
to your dollar prompt then what you have
to do is you have to press the key Q and
if I press Q here then I get my prompt
back and the shell behaves as if nothing
really happened so that's about man
the next command that we're going to
check out is the banner come on now
banner is used to well you know generate
fancy text if I type in banner and if I
type in something like I
a bad programmer something that sort if
I pressing the enter key then you see
that I get this text display in the form
of hashes and I is here you cannot see
the well the upper bar of I I would have
to scroll up my screen slightly to help
you guys see it so there's I for you and
then I'm a bad programmer so that's what
banner does now you can see that
whatever I placed space in the sentence
that I want wanted to print banner
interpreted the space as a newline now
if you want to avoid that and what you
can do is let me first clear the
terminal for you you can type in banner
and whatever thing you wish to display
on screen you can put it within double
quotes that would tell banner that what
you're going to get as an argument now
is a single phrase or a sentence so
don't split it up on multiple lines now
if I type in something like bye bye and
press ENTER you see that it's being
displayed on a single line and I have my
space character in here but the
limitation with this form of displaying
is that banner only displays 10
characters on a line no matter what the
size of your terminal is so if I would
use anything more than 10 characters
like you know what should I put here the
bad tutorials which is the name of my
channel you see that I just have the
space bad which makes for seven
character space that makes 8 + tu which
indoor makes 10 characters so that's the
limitation with using double quotations
now that's enough about banner it's a
command a I don't think we'll be using
at all in future but you know it exists
so I just spoke spoke about it the last
command that we are going to check out
in this tutorial is the compress command
now what I have done is
I have created a text file I basically
wanted to create a file with not one
sentence or two but with quite a lot of
text so I just went to the wiki page of
UNIX and I copied this text from there
in my file and it's called test file and
I currently have it in my home directory
now I'll show you guys the properties of
this file it has a size of 1915 bytes
and it's a plain text document and it's
in my home folder ok cool now if suppose
I want to reduce the size of this file
from 1915 bytes to if you know anything
less than that the command that I use is
compress now I type in compress at the
terminal that's what SS and I'll use the
option hyphen we which basically means
that after the command has been executed
the shell will display a message about
the percentage of compression that it
has achieved and then I'll type in the
name of my file which is test and I type
in sorry press the Enter key and I see
that compressed displays this message to
me test has been replaced with tests or
Z and the compression achieved is thirty
five point seven seven percent what this
means is if I would go in my home
directory I see that firstly the icon of
my file has changed the name of my file
has changed from test to test dot Z and
if I would see the properties of this
file then you can see that the size now
is no longer 1915 by its word but it's
1230 bytes so that's a significant
amount of compression that you've
achieved now if suppose I wish to view
this file then I cannot simply use my
cat file anymore sorry cat come on
anymore if I try to use it then I just
get non-printable characters but there
is a way around that you can use Z cat
and well let me first clear the terminal
and if you use a Z cat and type in the
name of the file which is Taz or Z and
press the Enter key you see that you get
your text file Tex back
if you want to convert your file back
from the compressed version to the
uncompressed version then the command he
uses uncompress I type in uncompressed
and the name of my compressed file if I
press the Enter key
nothing really shows up but I can go
back to my home folder and see that my
files name has been restored the icon
has been restored and in the properties
you can see that it has the same size as
before so there you go those were the
commands that I kept for this tutorial
three of them and all three important
man being the most important and you'd
be relying on it heavily so please make
a note of it and it's easy to remember I
don't think any of you will ever forget
how to use man it's the most simple
simple command to use and that's it for
now I'll see you guys in the next
tutorial and hopefully in the next
tutorial we'll begin our discussion on
shell programming and we'll probably
even create our first shell script so
see you guys in the next tutorial thank
you so much for watching this one and
please subscribe to my channel