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In this lesson you'll learn how to use the most important features of the said Command said stands for

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stream Ed and its use for well editing streams.

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You might not be familiar with the term stream but if you performed in the IO redirection or piping

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you've been using streams you can think of a stream as the data that travels from one process to another

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through a pipe or from one file to another as a redirect or from one device to another so you can think

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of standard input as the standard input stream standard output as the standard output stream and standard

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error as the standard error stream.

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By the way these data streams are typically textual data the set command is used to perform basic text

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transformations on an input stream.

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For example you can use said to substitute some text for other text remove lines append text after given

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lines and insert text before certain lines said differs from other editors such as vim emacs and nano

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in that it's used programmatically.

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Of course you can substitute some text for other tax remove lines append texts after given lines and

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insert text before certain lines using them but that requires interaction from a human.

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Sure you can write macros to perform these functions in vim but you have to have someone to start them

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and then execute the macros which said you can programmatically perform these edits without the need

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of interaction.

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And this makes said ideal to be used in shell scripts for example.

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The most common use of said is to act as a command line version of Find and Replace.

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I'm going to use this particular application of said to teach you the basics of the said command.

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Notice that I said said Command said is a standalone utility and not a shell built in.

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We can prove this by using the type shell built in

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so you can see that when you type said in press enter the user been said program will be executed of

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course for standalone commands you can use man to get help and documentation on how to use that command.

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So let's quickly look at Said's man page as we've already mentioned said is a stream editor the man

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page says it's used for filtering and transforming text.

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If we look at the synopsis section of the man page we can see that we can execute said with zero or

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more options followed by a said script and optionally followed by one or more input files.

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So let's exit out of this man page by typing Q and get to our first said command.

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Let's create a file to work with real quick.

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Let's do this

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make sure our contents made it in the file I'm sure did.

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But let's just prove it here by carrying that file.

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So sure enough it says Dwight is the assistant regional manager and that's the text that's stored in

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manager Dot T X T.

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Now as I said a minute ago the most common use of said is to act as a command line version of finding

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replace let's say you want to replace the text of assistant with the text of assistant to the to do

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that you would use the substitute command and said the substitute command is represented by the character

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s.

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So let me show you how that works.

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We'll start out with her said command.

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Next we'll put our asset script in single quotes.

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We'll tell said to perform a substitution by specifying the letter S after the s we use a forward slash

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followed by the text we want to substitute and then a another forward slash.

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In this case that text is assistant.

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By the way the forward slash is acting as a delimiter and the text between the forward slashes is called

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the search pattern.

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This search pattern is actually a regular expression so you can make very advanced searches if you want

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to.

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In this case we're keeping things simple to demonstrate the concept of finding and replacing some text

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using said.

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Next we'll type the text that is going to replace the previously specified text.

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We want to change assistant to assistant to the so we'll type this

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next we'll close our substitution with another forward slash.

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We'll call this text the replacement string that is the end of our set script so we'll supply the closing

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single quote.

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Finally we'll tell said what file to use as input and this example that file is Manager dot t t when

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we execute the command you can see that the text of assistant has been replaced with Assistant to the

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original text is Dwight is the assistant regional manager the text displayed after being transformed

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by our set command is Dwight is the assistant to the regional manager.

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Notice that I used the word displayed I used it very intentionally here in this example said is not

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altering the contents of the file it's just sending its output via standard out which is our terminal

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we can prove that the original file is unaltered by looking at its contents said can alter the contents

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of the specified file and we'll get to that shortly but first let's look at another example of using

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said to find and replace text.

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Let's use this text to work with

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let's change the text of my wife to said

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in this example we didn't reuse any of the text that we searched for.

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Instead we completely replaced it with brand new text.

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It should probably go without saying that said is case sensitive by default.

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So here's an example of that

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notice that the lower case text on my wife was not substituted.

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That's because it wasn't an exact match.

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If nothing matches said doesn't perform any alterations and therefore the text is returned without alteration.

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If you want to perform a case insensitive search you'll need to supply a flag.

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So really the format of the said s command is this

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you have s a forward slash and then a search pattern.

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Another forward slash to terminate the search pattern in the replacement string.

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Another forward slash and then any flags you want to use.

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So I'm just going to type control C here because I don't want to execute that command I just want to

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quit that command line there without running it.

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So we're going to supply the ie flag to the command which you can think of as standing for insensitive.

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Now the text gets replaced because you told said to ignore case by the way and it strikes me as a little

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funny.

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You can also use a capital I as the flag to do this in sensitive case matching.

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So this command works as well

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let's add some more lines to our loved text file and see how said handles that

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notice that I've used to greater than signs and that causes texts to be appended to the file if I just

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use one.

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It would have truncated the file but I was careful here and used too.

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So we can look at our contents here and sure enough there are two lines in that file.

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So let's go ahead and add a third line.

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Okay.

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There it is.

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Love dot text with three lines.

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Now let's try the replacement command again.

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What happens is that said reads one line from the file and executes the set commands in quotes against

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that line.

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Next it moves on to the next line and does the same thing until it reaches the end of the file.

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You'll see that my wife was replaced by the words said on lines 1 and 3.

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Line 2 was unchanged because our search pattern of my wife was not found on that line.

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Let's add yet another line to this file to demonstrate another important concept.

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Now let's run the replacement command again

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notice that on the last line only the first occurrence of my wife was replaced.

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It says I love said and my wife loves me.

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Also my wife loves the cat by default said just replaces the first occurrence of the search pattern

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on a line to override this behavior.

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We'll need to use the G flag.

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You can think of G as standing for global as in a global.

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Replace

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now the last line says that I love said and said loves me.

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Also said loves the cat.

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If you want to replace the second occurrence of the search pattern use the number two as a flag.

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If you want to replace the third occurrence use three.

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The fourth use for etc. etc..

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So let's do this

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this time.

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None of the first occurrences of the text my wife were replaced but only the second occurrences were

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on the line where only one occurrence of my wife existed.

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That line was unaltered because there was no second occurrence on the last line where my wife appears

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three times only the second one was changed by the way.

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When I'm saying things like change I don't mean that the original file has changed again.

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The contents of the file remain the same sometimes you don't want to just see the output displayed to

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your terminal but instead you want to save that output.

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One way to do that is to redirect the output of the set command to a file.

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Of course this isn't anything unique was said.

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It's just how Linux works with any command.

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So let's create a new file called my new love.

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Don t x t

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again the original file is left unaltered.

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So there you have it the original file with the original text and the new file with a redirected and

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altered text.

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If you want said to alter the file use the Dash I option to said which you can think of as in place

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editing if you want said to make a backup copy of the file before it alters it supply the same text

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right after the dash eye and said we'll append that text to the copy of the file.

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So now we have our original file named Love dot t x Tepe and another one named Love dot t t dot B A

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K said has performed an in-place edit of the original file so let's look at that now.

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So there you can see where said has replaced the text of my wife where appropriate given the command

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we ran.

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If we look at the backup file we'll see that it has the original text in it it's important that you

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don't use a space after the dash I option if you do you'll get an error.

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So let me demonstrate that here.

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So this is what not to do.

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Notice I'm using a space.

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This is going to cause an error.

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So sure enough we get an error.

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That is one little gotcha.

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You can avoid.

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So just do not use this space after Dash I.

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If you only want to save the lines where matches were made you can use the w flag followed by a file

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name.

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So let's do this let's change love to like we'll do a global replace so that no matter how many times

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love appears on the line it will get replaced by like and then we'll use the w flag and a file name

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after it so we'll use like dot t x t and then the file we're going to use as input is love t x t in

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this example said displays the entire contents of the loved text file to the screen with any replacements

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it made and it created a new file named like dot t t that only contains the lines where the replacements

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were performed.

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So let's look at that like t text file now while we're talking about input and output.

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I would like to point out that said can be used in a pipeline instead of specifying a file to work on.

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The simplest example would be to cat a file and pipe that to said like this.

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That is the exact same thing as doing this.

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This is a very common pattern with Linux commands where they can be given a file to operate on or they

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can use the data sent through a pipe to operate on.

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We've seen this with other commands such as cut OK sort unique and others command a pipeline thing is

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very powerful because you string as many commands together as needed to make the data look the way you

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want it to.

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I'm going to generate some text to work on with an echo command

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let's say we want to change a forward slash home forward slash Jason to be forward slash export forward

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slash users forward slice Jason C.

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The challenging thing about this is that the strings we want to manipulate have Ford slashes in them

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and we've been using Ford slashes as a delimiter with said one way to get around this is to escape the

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Ford slashes.

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I'm going to show you a better way in just a second but let's see how we would do it with escaping first.

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Now to escape a character simply precede it with a backslash

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so we're starting our search pattern with the forward slash.

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But the next Ford slash isn't a delimiter so it needs to be escaped.

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So if we're going to use a backslash to escape this forward slash same thing again here.

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So now we end our search pattern with a forward slash and again R next pattern starts with a Ford slash

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we have to escape it here again we're escaping a Ford slash and yet again.

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And then finally we're closing out our command here.

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That feels like a lot to keep straight and it's easy to make a typing mistake in this situation.

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A nice feature was said is that you can use any character as the delimiter.

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So let's use a pound sign instead.

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So the first character that follows the S will be treated as the delimiter no matter what that character

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is.

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So let me give you an example here.

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I'm going to use a pound sign and now said we'll treat that pound sign as the delimiter.

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So now I can just go ahead and specify the text I want to use here and my search pattern which is Ford

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slash home.

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Jason close that search pattern and now the replacement string is Ford slash export Ford slash users

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Ford's less Jason C and then we'll close out the replacement text there with a pound sign and the single

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quote finishes are said script command there.

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So let me hit enter.

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And so as you can see that works as well.

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Just to prove that any character works as a delimiter.

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Let's use another character how bout a colon this time

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OK that works as well.

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So you get the idea if you need to use Ford slashes and your search pattern or replacement text choose

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a different delimiter other than the forward slash.

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All right.

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So enough with actually performing substitutions.

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Let's take a second here to talk about when you would actually want to perform them.

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One idea is to use templates or template files.

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For example if you are constantly deploying new Web sites and use the same configuration except for

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the Web site name then it would be a good idea to create a template file that contains all the standard

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configuration and a place holder for the Web site name.

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Then you could use said to simply replace all the place holders with the actual Web site name.

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When you're ready to deploy it.

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Another example of when you could use said substitution feature is when you are migrating from one server

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to another or when you are using a restore of one server to create another new server.

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In this example you would need to find and replace the old hostname with a new one for all the files

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in the Etsy directory files.

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This is Etsy hosts and maybe Etsy hostname and there could be others depending on that systems configuration.

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Yet another example would be when you are copying configuration for a given service from one host to

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another.

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You might find yourself doing this especially if you are working on clusters.

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You would just copy the configuration from one host to the new host that you are adding to the cluster.

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Typically you'll need to change the hostname in the configuration file and you could use is said to

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do this for you said would be especially helpful if that hostname appeared many times in that configuration.

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Okay so that's pretty much it.

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With the said substitution command let's say we want to remove or delete some lines with said well how

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you do that is with the D command.

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Let's review the contents of our love dot text file

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let's say we want to remove the line that says this is lying to us you have to do is come up with a

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search pattern that will match that line and not the other ones.

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So we could use a search pattern of this because the word this only appears on the line.

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We want to delete our search pattern is this.

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And the command is D

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so to be clear here the syntax is a delimiter.

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And by default we use the Ford slash as the delimiter followed by the search pattern and a closing delimiter.

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Again this is a Ford slash and finally a D which tells said to delete the line that matches the provided

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pattern.

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We can see that this worked as our desired line is gone.

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Let's say we want to remove all the lines that contain the search pattern of love.

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Here's how we would do that.

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So now all the lines that match love are gone.

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Sometimes when I'm working with a configuration file with many lines I'd like to strip out the comments

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and blank lines to compact the output.

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That way I can see just the configuration and nothing else it makes it easier to read at least it does

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for me.

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I'm going to create an example configuration file to demonstrate this concept with

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so this sample made up configuration file is just a few lines long but you can easily imagine one with

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many many more lines.

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First let's remove the comments.

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Remember that the search pattern is actually a regular expression in regular expressions of the carat

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symbol matches the beginning of a line it matches a position and not a character.

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So if we want to match all the lines that start with a pound sign we use carat pound sign.

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This makes sure we don't accidentally delete lines that have actual configuration at the beginning of

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the line but have a comment later on that same line.

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So now we have our configuration file without the comment lines but we still have the blank lines to

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delete a blank line we'll use another regular expression

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again the carat symbol matches the beginning of the line the dollar sign matches the end of the line.

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So carat dollar sign matches a line if the beginning of the line is immediately followed by the end

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of the line set another way carat dollar sign matches blank lines.

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So we know how to do the two things we want to do.

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But now we need to do them at the same time we need to combine them to use multiple said commands or

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said expressions we can separate them with semicolons

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for each line said we'll perform the first command which deletes lines that start with a pound sign

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and then the second command which deletes blank lines to show you that you can combine different types

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of commands let's perform a substitution.

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Let's change Apache to h t TPD

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so that particular commanded three things are deleted lines that started with a pound sign the deleted

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blank lines and it also changed Apache to h t TPD just to be thorough.

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I want to share with you another way to execute multiple said commands.

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Mainly I want to show you this just in case you happen to see it in a script or in someone else's work.

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That way you'll know exactly what is going on.

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So the other way to do this is to use multiple dash e options to said one for each said command to execute

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said also allows you to specify a file containing the said commands.

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So let's demonstrate this now.

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I'm going to create a file using the echo command here of course you can use an editor if you want to

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so what we've done here is put one said command per line.

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Now we'll use the dash f option and supply the path to the file that has the said commands in it so

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we can do this said dash F.

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And then the path to our file and then the path to the file that we want to use as input.

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So here again we get the exact same result before we wrap up this lesson on said.

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Let's take a look at using addresses an address determines on what lines the said command will be executed

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on if no address is given.

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The command is performed on all lines an address is specified before the said command.

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The simplest of addresses is a line number.

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Here are the contents of our sample configuration file to refresh our memories here's an example that

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will only execute against line 2 of the file

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as you can see the search pattern of Apache was replaced by H T TPD only on the second line.

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There's also a match on the last line of the file but that was left alone because it didn't match the

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address of line 2.

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By the way some people do not use spaces after the address.

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So this is the same command without that extra space.

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You can also use a regular expression as an address to match lines.

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Let's say you want to replace Apache with H TPD but only on lines that contain the word group

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as you can see Apache was changed to HDTV D.

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Only on the line that also contained the word group.

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You can also specify a range by separating to address specifications with a comma.

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For example if we wanted to change the word run to execute but only on lines 1 through 3 we would do

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this.

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There was only one occurrence of run from lines 1 through 3 and it was changed the occurrence online

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4 was not.

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So let's extend the range to include line 4

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again.

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You can use regular expressions instead of line numbers.

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Let's say we want to change run to execute.

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Starting with the line that matches pound sign user an ending at the next blank line.

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So here's how we would do that.

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So there you can see that every instance of run that was in between the line that started with LB user

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and the next blank line was exchanged with a text execute.

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Of course there was only one match so only one substitution was made but you get the point.

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You could specify a large portion of the file if you wanted to.

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One starting point with a another starting point as your address and then change everything in that

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section while leaving everything else alone.

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It's very powerful to use addresses was said in this lesson you learned the most common use case of

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said which is to perform text substitutions.

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You learned how to replace specific occurrences as well as how to replace all occurrences of the search

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pattern.

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In addition to finding and replacing texts you learned how to delete text with the D command.

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From there you learned how to save the alterations performed by said as well as how to make backups

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of the original file so that your data is safe.

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Next you learned three different ways to execute multiple said commands on the same set of data.

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Finally you learned how to use addresses to work on very specific sections of input.