Shell Scripting Tutorial-43: Search Patterns Using 'grep' 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 43rd tutorial
in the series of tutorials on UNIX shell
scripting in this tutorial we're going
to check out a command and it's called
grep and grep is a pretty important
command and I'm surprised why I didn't
discuss it with you in the first 15
tutorials in this course that is before
we started our discussion on shell
scripting because you know it's a
command that deserves a special mention
it's pretty amazing and shell
programmers use it so much that you know
once you learn shell scripting you will
be relying on grep for a lot of things
so let's not waste any time for the sake
of this tutorial what I have done is I
have created a text file called text
underscore file and I've saved it in my
home folder and this file has the lyrics
of the song money by Pink Floyd now in
case you haven't heard the song I would
suggest you guys to do that because it's
a pretty amazing song it's one of my
favorite songs and Pink Floyd is my
favorite band so you guys haven't heard
it check it out but that's not important
for this tutorial so you can now put
that on hold the time mean so anyway
grab we use grep to search for patterns
in text files right so what I mean by
that is if suppose I want to look for a
word or a few words in this text file
what I would do in text editor like
Microsoft Word or you know even if I
have a PDF document that's made of text
what I would do is I would type in so I
press ctrl F and then I would search for
my word but if you want to do that to
the terminal what you would have to do
is you would have to use the command
grep and that is GRE P and it actually
has a full form you know I guess it's
called globally searcher regular
expression in printed or you know
gradually search regular expression
printed I don't know what the whole form
is maybe you guys can you know google it
and let me know what it is but that's
not important what what is important is
that we should know how to use it
so anyway you have to type in grep then
followed up with a space and then typing
the word or words that you want searched
and if you want to search more than one
words than you would obviously
to put them within double-quotes but
what I'm going to do is I'm going to
just search for the word money in my
five texts underscore file and when I
press the Enter key you see that nothing
gets displayed and that's because in my
text file there is no line in which you
have the word money just the way as I
have typed laid in my command I have
used all lowercase letters and you would
see that in my text file wherever money
appears at least the first alphabet that
is M of money is in a capital case right
so the way I would get around that
problem is by using grep with the option
- I and - I does grip - you know become
case insensitive that is ignore case and
you know if you have money in your text
file you know no matter how you have it
whether you have it in all lowercase
letters or all uppercase letters you
know it doesn't matter how you have it
just display the result I mean right so
if I would not press the Enter key you
would see that all the lines in which I
have the word money are being displayed
right and if I would also want to know
the line numbers of these lines then I
would have to use the option hyphen n
hyphen I right so now you see that line
numbers are also being displayed and you
can match these line numbers to the line
numbers that your text editor is showing
you like for example I have one on line
one I have money get away and if I show
you guys the file in my text editor you
would see that on line one you have
money get away right so I mean there are
just six lines it's hard for me to
believe that there are just six lines in
the tax file which has 52 lines in total
in which there is the word money and you
know it's surprising because the song
itself is called money so anyway those
are the two important options with grab
and the third option that we're going to
check out is the - C option and - C
option is used to not display the lines
but just to you know have a count of the
lines that contain the keyword or the
pattern if you're searching right so if
I would let me first clear the screen so
if I would use - C option here along
with the options - I and - n
and press the Enter key you would see
that I get six is the output and that's
because there are six lines in the text
file that have the word money and the
last option that we're going to check
out program in this tutorial is the - we
option and - we basically it does grab
to reverse the match that is you know
consider only those lines for output
that do not have the word money right so
if I don't use the - we option then the
lines that have the pattern that I am
searching are displayed but if I use the
- we option then all the lines I do not
have the pattern are displayed so let me
show you guys what happens when I use
the - B option with - C - I + - n you
see that 46 is being displayed and that
means that there are 46 lines in my
files that not have the word money and
if I would use - we are without the
option - I and sorry - N and half and C
and you would see that all the lines
that not have the word money are being
displayed so there you go as you people
must have noticed grep is a pretty
powerful command and it comes with loads
of other options and if you people want
to explore grep in greater detail what
you guys can do is you can now view the
man page of grep and that you can do by
typing in man space grep in your
terminal and there you go you would see
the man page and there are so many other
options you can check out the version of
grab and then you can check out what the
- why option does or the - captaincy
option does so there are loads of
options that you can check out and you
guys can have a little bit of fun with
grep it will certainly help because in
this course we will be using grep for so
many things and for sure so that's it
for now
I'll see you guys in the next tutorial
and I can assure you that it will be
important and interesting as it always
is thank you so much for watching this
one and please subscribe to my channel