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In this lecture we will cover a group mighty tool.

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Firstly let's open fire.

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We have created in previous lecture and let's say that for some reason even the fine line of each contains

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a word.

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Second imagine did your file has more than ten thousand lines so searching manually would be horrible.

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For that reason we can use grep.

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So open terminal and write command and grep followed by a bottom.

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You are searching if you specify a spartan and more rewards.

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Don't forget to use double quotation marks and Dennis specify name of a file that the grep should look

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for that but.

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So in my case.

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Article and icy output line which contains words second and similar to WC command grep is also often

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used with cat command.

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Using pipe.

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Please don't be afraid that you don't understand by being now it will be colored lightly.

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But basically what we are doing here is moving output of command.

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In my case four lines from file called article and we are moving that output to grab command to process

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it and search for a bottom.

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In our case second in my article file there were only four lines.

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So now I can work with something bigger.

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For example passport file which contains all user's data for my computer and almost at the end

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is mentioned user Richard.

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Which is me.

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So let's say that I want to display only this line from that file how to do that I can use God password

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file by grep Richard and then I run it.

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I see only desired output the same output I can get without by being using grep.

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So grep Richard and specify the file in my case password file and the output is same as previously

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do we have another option when using grep he we have.

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So let's take a manual

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and here is something which is also used very often and it is parameter old.

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So let's find it here

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barometer all brains only matched parts that means it doesn't brings a whole line where a button was

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found but only the part which matched the pattern.

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So let's state we can now close the manual and we can write grep

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with parameter all

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Richard because we are searching for pattern Richard and specify the file and now we see printed Richard

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three times as it was found three times and other parameter which can be also used is parameter C or

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count.

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So let's search it.

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Here it is.

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It suppress normal output and brings a count of matching line

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so if I tried I should get number one as only one line was found which contains name Ed

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also what is good to mention is parameter V.

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Parameter v selects non matching lines for the reason we can use it.

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Let's see.

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Create new file and call it config

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open data file for editing.

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And make their few lines starting with hash symbol

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and then we can make one line which not start with hash.

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And then two lines starting with hash again and again we can use some normal line without without the

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hash at all.

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And again two lines started to put hash and then we save it

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we can now use get with parameter V

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and I said but then we can use hash symbol and now back to a file in my case file config

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and when we run it we see printed only two lines which has no hash inside which is good.

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Imagine that you have 1000 commented lines and only two lines which are not commanded.

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So for searching those two lines this parameter V is really good when checking the manual for grep command

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we see button but button can be not only somewhat but also a regular expression.

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So let's try with some regular expression.

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So type of grep

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followed by double square brackets and inside them call column digit Col on which is a regular expression

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and represents all numbers.

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So if in some line is no will get printed in line and if you see printed line with IP others which has

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numbers.

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Great.

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Now let's edit our config file and add another line with some number

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save that file

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and then running grab command again we see now printed two lines.

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Great maybe last thing to mention here is option how to print detailing or a leading context after or

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before matching lines.

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This option might not work on all grep versions but the vast majority should have it.

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So we are a solution for context line control.

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In the meanwhile

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and here it is.

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For example parameter a pretty specific number of lines of trailing context after matching lines.

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Wow.

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Parameter B brings bleeding context so let's use that and maybe the best instead of talking would be

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to some.

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Example.

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So we can now print two lines which are after matching lines containing no

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so for IP address it would be comment command.

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And for number equals 5 would be only common because there is only only one line after it

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so write and grab with parameter a

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after that specified number of following line which would be included also in the output.

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And we are searching for number in config file.

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And what we see is exactly what I have told you.

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We see IP address and following two lines and we see number is equal to 5 and following one line because

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there is no other line in that file if we use parameter B we see printed two lines before matching lines.

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That means before lines which contains number for IP address line which contain a number we see printed

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two lines before and also for line number equals 5.

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We see printed two lines before.

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Good Please don't be afraid.

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Did I didn't tell you anything about the regal expression.

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Visual definitely covered lightly in much more detail.