Shell Scripting Tutorials-57: Know when users log in Part Two 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 57th tutorial
in the series of tutorials on UNIX shell
scripting in this tutorial we are going
to improve the script that we made in
the previous tutorial and I have it here
it's called check and has the extension
SH and the first thing that we are going
to do is we are going to check whether
the input that has been provided to us
that is the username that we stored in
the variable long name whether an
account of that username actually exists
on a system or not and obviously you
have to use grep to search and we are
going to search in the password file in
the EDC folder so I'll type in grep and
then I'll type in dollar logname and you
know since this is a string I'm going to
put it within double quotes and we are
going to check whether this can be found
in etc' / password right and what if it
if it is there then we not want grep to
display the pattern or the entire string
you know on screen so we are going to
redirect the output to the null file in
the DB directory and then we are going
to use if to check whether the exit
status of this command on line 4 is a 0
or not and I'm going to do by typing in
toward question mark - EQ space 0 right
and well if the exodus is 0 that means
that you know a user account does exist
you know with the login name that we've
stored in the variable log name and in
that case we are going to use echo to
display a message like wait right
because then the script is going to do
the other thing and that is it's going
to check know whether the user has
logged in or not and if it has then you
know it will display some message and if
it you know the user hasn't logged in
and it's going to wait for the user to
login and you know whenever the user
will login
you know display a message then so
that's why we are going to you know just
display a message like wait and what if
the exit status is in zero in that case
we are going to know get inside the else
block and we are going to display a
message using echo you know something
like user not found right and we'll stop
there and we move outside the if block
by typing in the keyword fi and that's
pretty much it that's a you know that's
the enhancement that I wanted to make to
the script and I bring up my terminal
and execute the script for you guys so I
have to type in SH space check dot SH
because that's the script name and when
I type in you know a user name that I'm
sure doesn't exist on the system like
Sam and press the Enter key it does me
user not harm right and I can get back
my daughter prompt by typing in ctrl C
clear the script and maybe I should you
know put in exit here because you know
we would not want to press ctrl C to get
our prompt back you would want the strip
to be that for us so I say this and I'll
bring up my terminal now execute the
script again and this time again with
the input Sam and now you see that I get
the message in my daughter from this
automatically returned to me right but
if I provide a valid user name like new
user to press the Enter key then I get
the message
wait this time right and let me open up
another terminal window and I can sue
those space log in and press the Enter
key type in my password and then the
user name of the account with which I
wish to log in and then the password for
that user account and I get my prom and
you see that I don't get a message
immediately and that's because the while
must be you know waiting for
you know the user login and since we've
used sleep 60 in our script it means
that you know the loop is going to check
every 60 seconds right so it checked the
ones when we execute the script and now
it's you know going to check again after
60 seconds so you know we have to wait
and you know it could be any moment now
and there you go it tells us that new
user to his log plane and new user to
was one minutes late in logging in right
so that's pretty much it in the next
tutorial again we are going to you know
make the script more efficient and I'm
going to make a few more modifications
so see you guys in the next tutorial
thank you so much for watching this one
and please subscribe to my channel