Shell Scripting Tutorial-26: Escape Sequences 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 26th tutorial
in the series of tutorials on UNIX shell
scripting in this tutorial we're gonna
check our escape sequences that you can
use with your echo command to modify its
behavior
now I've discussed echo in one of the
previous tutorials but in case you've
forgotten how to use it
I'll demonstrate it again to you guys I
have my terminal here and if i type in
echo followed with a space and within
double quotes if i type a string like i
am the worst teacher on youtube and if I
press the Enter key then on the next
line you would see that my statements
gets displayed right now what if I want
a code to display the statement but
display it in a different way what if I
want all these characters to be printed
in bold or what if I want them to be
printed in the reverse format that is I
want the text to be white in color but
the background to be black right or what
if I want to print some part of the
sentence on one line and the other part
of the sentence on another line now in
order to do such things I would have to
instruct echo and I would have to
instruct echo using escape sequences
because that is what echo understands
now what is an escape sequence an escape
sequence is basically a bunch of
characters and it always begins with the
backslash character and is followed by
one or more characters so what I'm going
to do in this tutorial is I'm going to
create a shell script now I'm gonna
demonstrate all the escape sequences to
you guys so I'll bring up my text editor
here and the for I typing in text I'll
save this file in my home folder I'll
give it the name s s ten dot s H since
this is the tenth script file in the
series on the first line I'll put a
comment something like escape sequences
and on the next line I'll use echo to
print a statement for me a world
what sup there you go and let me first
execute this shot script using the
terminal and show you guys what the
output is
[Music]
there you go my statement is being
displayed
now the first escape sequence that we
gonna check out is the slash n escape
sequence now what if I want this part of
my sentence to be on one line and this
part of my sentence to be on another
line it's very simple all I have to do
is put a slash and escape sequencer so
I've put a backslash character now
followed it up with the alphabet n n
here stands for new lines so if I would
save my file and if I would execute the
script you would see that part of my
statement is being displayed on one line
and the next part is being displayed on
a new line so that's what /m does n
stands for new line and it's really easy
to remember the next escape sequence so
we're gonna check out is a slash our
escape sequence and it's also called
curious return right and before I talk
about it I will demonstrate the output
so there you go what's happened is we
don't see the first part of the sentence
that's Hayward the comic actor and the
space we just see what's up so what has
happened is echo started printing the
statement and it printed this part
everything before encountering these
laughs our sequence and when it
encountered the slash our sequence I
thought that okay maybe everything that
I've printed before is rubbish and I
don't have to so what I'll do is I start
printing again and from the very
beginning of the line it started
printing this output what's up
not the output but this part of the
sentence right so a user would see this
as you know the first part of the
sentence has been ignored but that's not
the case what has happened is this part
has been printed once and when the slash
or escape sequence was encountered the
cursor was brought back to the very
first column on the line on which
this statement had to be printed and
this part of the sentence overlapped
this part right so I hope I made some
sense there I didn't properly explain it
though but I hope you guys caught it the
next one that we are going to check out
is the /t escape sequence and slash T or
horizontal tab is nothing but it's
basically a substitution for five space
characters so if you want to type in the
space part five times you don't have to
do that you can avoid that you just have
to use your slash t escape sequence
right so let me execute the script T you
guys there you go you see that the space
between the comma here and the W of
what's up is is six character as well
and it's because of the slash T and if I
would put another slash T over here then
you would see that the space would
increase wait a second what's happening
here clear the terminal first there you
go the space is increased so that's what
slash T does the next one that we gonna
check out is the slash V escape sequence
now slash V is backspace and it
basically omits the character that
appears immediately before it so if I
would put slash B here then the space
would be eaten up if I would put another
slash B then the comma before the space
would be eaten up now what if I want to
eat up the entire word worth it has what
five characters so I would have to put
five more backspace sorry slash be
escape sequences so one two three four
five now save my file and I clear the
terminal and execute the script and
there you go you see that world and the
comma and the space after it has been
omitted and I just have hey what's up
here right so that's /b for you and the
last set of escape sequences are written
and check are in this tutorial are used
for changing the manner in which the
text appears that is if you want to
print your statement in bold what you
would have to do is you would have to
put a backspace before your statement
begins back slash sorry and then you
would have to type in the code 0 3 3 now
this is something that you would have to
remember it's a it's a rule it's a
format that you have to keep in your
mind right so I have to put zero three
three here and then I'll have to put the
left opening bracket which is this
symbol right here right it's not the
left open brace but it's the left open
bracket right and after that I'll have
to type in the chord for the bold escape
sequence which is one M now I know that
this can be slightly difficult to
remember but would practice it would
stick in your mind and you won't have to
refer to a guide or the man page with
ICO or anything for it it'll just stick
in your mind trust me so there you go my
sentence is now ready and if I execute
the script for you guys and you would
see that my statement is being displayed
in bold but not just my statement but
even the dollar prompt the thing that
happens to follow the statement is also
being printed in bold now this is not
something that I desired right
I want my dollar problem to be printed
in the normal way so what I have to do
is at the end of my statement I'll have
to instruct echo to get back to the
normal mode of compression and in order
to do that I'll have to type in the
backspace character so a backslash
character and then 0 3 3 the code again
the left opening bracket again and I'll
have to type in 0m instead of 1m in
order to instruct echo to get back to
normal moon
I save my script file and I clear the
screen and I'll execute the script and
there you go you see now that just my
statement is being displayed in bold and
my dollar prompt is being displayed
normally so that's how to get back to
the normal mode the last escape sequence
are we gonna check out in this tutorial
is to print this string in the reverse
format and if I change one him here to
7m and save my file and execute it then
you would see that the background of my
sentence is black and my sentence text
is white in color and that's because
I've used the reverse video format right
so everywhere else on the page you can
see that the
background his wife in the Texas back
but just for my sentence echo has
changed the settings it has changed the
background black and it has changed the
text color to white now there are Lord
for the escape sequences that you can
use with echo to rev up your text output
but then these are the most commonly
used escape sequences and you would find
using them a lot and in the future maybe
in this course will check out more
escape sequences and as and when we
would use them I'll discuss them with
you but for the time being I just want
you guys to practice these escape
sequences and in the next tutorial we're
going to check out the t put command and
we learn how to do similar things using
teapot and teapot is very versatile
elsewhere and is very important so don't
miss that tutorial and thank you so much
for watching this one and please
subscribe to my channel I'll see you
guys in the next tutorial