Shell Scripting Tutorial-35: Count The Number of Characters in User's Input in Your Script Video Lecture | Shell Scripting: Discovering to Automate Command-Line Tasks - Back-End Programming

hello guys my name is Martin and welcome
to my channel this is the 35th tutorial
in the series of tutorials on UNIX shell
scripting now in the last tutorial we
learn to use the logical and operator
and I told you guys there in this one we
will be checking out the or operator but
instead what we're gonna do is we're
gonna learn a new technique and that's
because the technique that we're going
to discuss in this tutorial we will be
using it to build our script for the or
operator right so this is essential and
in the next tutorial we'll get to our
discussion on all so I have my text
editor up here and I have saved this
file in my home folder given it the name
count and the extension SH as you can
see and what this script is going to do
is it's gonna ask the user to enter a
character and then it would check
whether just one character has been
entered or more than one characters have
been input and if one character has been
entered then it will display one message
and you know if more than one characters
have been entered then it will probably
you know display a message like invalid
input right so it's going to be a short
and sweet script and let's get started
wait so I'll use echo on the first line
to ask the user enter character right
and I'll use read to store the input in
the variable var and on the next line
I'm gonna check whether the number of
characters in var is 1 or greater than 1
now I'm gonna use WC with the option - C
here and WC is the word count utility
and I've used - C here because I am
interested in calculating the number of
characters and WC comes with 3 important
options - L for lines - W for words and
- C for characters and in case you
people have forgotten how to use WC or
if you have missed the tutorial on WC
then I put the link to the tutorial in
the description below and you can watch
it right so WC receives input in text
form right so if I would simply type in
the name of my variable here daughter
bear
then it won't make too much of the earth
sense to WC in fact it won't make any
sense at all
so what I would have to do is I would
have to echo out the contents of the
variable dollar buy here and then I
would have to use the pipe symbol to
send that output to WC so what I mean is
Ecuador would simply echo out the
contents of the variable and then you
know whatever will be a crowd would
become the input to the command WC - C +
WC happens he would return the number of
characters right and since we are
interested in the total outcome of this
combination of commands we're gonna put
this entire thing with in reverse codes
or acts and graves right and now we are
gonna use the - EQ operator and compare
this numeric value to - and the reason
why we've used 2 here and not one is
because when you use read to grab users
input it basically appends the carriage
return character to your input right and
I'll demonstrate that to you guys I have
my terminal head and if I would simply
type in read space num and press the
Enter key then my cursor blinks and
waits for me to type in something right
so if I would let's say type in 456 I
would have to press the Enter key to get
back my dollar prompt and when I press
the Enter key my variable num doesn't
just get the value 456 but it gets the
value 456 plus the carrier's return
character and if I would use echo to see
the contents of my variable num here
then you would see that I get 456 and my
dollar prompt gets displayed on the next
line and that's because there's a
newline character at the end right so if
that wasn't the case would read then we
would have obviously compared our
numeric value to 1 but since there is
one additional character there I would
have to compare the value to do I hope
you people have understood this and I'm
gonna well make this an if statement
because we have to
play a couple of stupid messages and the
next line would go the key word then and
I'll use echo to display you entered
character and if we go inside the else
block then the user will see a different
message invalid input all right and I'll
terminate my if block by using the
keyword F I save this file and I'll
bring up my terminal clear the screen
for you and what was the name okay
assets face count toward Sh and yeah it
asked me that I have to enter a
character so if I type in J and press
ENTER then it tells me that I am too low
character and if I well type in four
five six seven eight nine and press the
Enter key then it tells me invalid input
right and you can work around with the
shell script and you can you know type
in random input and see that it actually
does what it's supposed to do right so
there you go
I will be using this method in the next
tutorial and that's why I've discussed
it here so I hope you people have
understood how to use WC - see where the
echo I'll maybe go over it once again
I've used echo dollar barrier because I
wanted to transmit the output of this
statement to the output sorry to act as
the input of WC - C and since both these
are actually commands WC - C is a
command that uses the input that's
provided by the output of the echo
dollar where I've used the pipe symbol
here right and the pipe symbol you can
find it over the enter key and the
action grace you can find them you know
next to the key one on your keyboard
right and we've used the both these
things before so I'm sure these are not
new concepts to you and I've I'm sure
you people have understood why have you
compared the numeric value to two
instead of one right so thank you so
much for watching this tutorial I'll
meet
guys in the next one and please
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