Shell Scripting Tutorial-31 Run Checks On Files Video Lecture - Shell Scripting

hello guys my name is mother and welcome
to my channel this is the 31st tutorial
in the series of tutorials on UNIX shell
scripting in this tutorial we're gonna
discuss files and by that I mean we are
gonna study the different types of files
and how to run file checks in shell
scripts so files can be character files
the files that you create through your
text editor are character files and they
can be blog special files and blog
special files are files that have binary
code in them like image files or video
files right and there are a lot of other
attributes that you can associate with
your files such as permissions right
whether you have read permission or
write permission or execute permission
to the file and whether the size of the
file is greater than 0 or not right or
if the file is a directory file in UNIX
or deities are also treated as files so
if I would bring up my home folder here
for you guys then this folder here
documents is a folder but it is treated
as a file right so it's a diet free file
and then I have the shell script here
which is a character special file right
and if I show you this file this is a
file with the extension dot DBF and this
file cannot be open through my text
editor so this is a blog special file
and if i would create an empty file here
then that would be a file with size 0 so
that is it i mean you guys know the
various kind of files that can be and
you also are aware of file extensions
and how extensions make different make
differences to the file types all right
so I'm not gonna bore you guys further
on it what I'm gonna do is I'm gonna
create a show script and show you guys
how to run checks on files so what this
script is going to do is it's gonna ask
the user to input name and it's gonna
check whether the name that has been
input is the name of a file in the home
folder right it has to be the name of a
file or a directory so the first thing
I'm gonna do is I'm going to use echo to
display a message like enter a name
right and I'll put a column at the end
and the /c escape sequence
on the next line I'll use read to store
that name in a variable F name okay on
the next line I'm gonna use my square
brackets again and I'm gonna check
whether the name that has been input is
the name of a file and the way I do that
is by using the option hyphen F so if I
put in - F space dollar F name which is
the name of my which is the name that
has been just provided to me by my user
then the shell would check whether a
file exists of this name or not and if
it does then it would display a message
because I'm gonna put this thing in an F
block right so on the next line would
come the keyword then and I would
display a message like you indeed sorry
entered a file name right and if it
isn't a file but something else let's
say if it's a diet tree then it would
display another message like echo don't
provide me crazy
inputs all right and then I'll close my
block by typing the keyword fi I save
this file I've already saved it it's
called file - test or SH and it's in my
home folder so I'll bring up my terminal
here now I'll execute the file it asked
me for a name right so if I type in
music which is not a file but a diet
tree in my home folder and press the
Enter key then it displays this message
to me don't provide me crazy inputs but
let me first create a file using touch
and I'll call it test and then clear the
terminal and execute the script and this
time I'll provide the name test as the
input and when I press the Enter key it
tells me that you indeed enter the file
name because I have just created the
file test right but if in my file I
wanted to check not profiles but for
diet wreath and that reason all I
have to do is change the hyphen F option
to - D right so if I would make this
modification then if I execute my script
and now provide the name music then it
would tell me that you indeed entered a
file name and it doesn't tell me that I
provided some crazy input right so there
you go to check profiles you use the
option hyphen F to check for diet please
you use the option hyphen D and there
are Lord for their options that you have
you know at your disposal if you're
running file checks for example to check
for character special files you use -
seen to check for blog special files
such as images or video files you use
the option - B and to check whether you
have read permission you use - are for
write permission you use - W and for
execute permission you use - X okay and
am I missing something
yes of course I am if you want to check
whether the size of your file is greater
than 0 or not then you would use the
option hyphen s right and this is
probably something that I will show you
guys because it's very important so what
this if statement is going to do is it's
going to check whether the file dollar F
name has a size greater than 0 or not if
it has a size greater than 0 then we get
into the if block and we will display a
message something like the size of the
file is greater than 0 okay and if the
size is not greater than 0 then well
we'll just let it be don't provide me
crazy inputs okay because we don't have
time to change that so I'll clear my
terminal and I'll execute the script and
I'll provide the name test the empty
file just that I just created using
touch and it tells me that don't revise
me provide me crazy inputs however if I
would use cat and in put some text in my
file test something like random and then
press control D I just for ado
type in some text in my file so that
it's size becomes greater than zero I'll
clear the terminal execute the script
again and oops
provide the name test as input and this
time you can see that it tells me that
the size of the file is greater than
zero so there you go you've learned to
use the hyphen s option the - f - D
option and it's your assignment you have
to create a file and play with the other
options that are mentioned that is the -
our W and X and also the - C and - B
options right so if you practice all
those options in your subscripts then
you will be a pro at running file checks
and that's all I wanted to talk about in
this tutorial thank you so much for
watching this one and I'll see you guys
in the next tutorial and please
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