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In the previous exercises you been writing scripts to do things like add users Well now it's time to

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do the opposite.

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We're going to write a script that deletes users and actually this particular Scrubb not only deletes

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users that can disable them and it can archive a user's home directory.

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So the first thing of course we need to do is come up with a little requirements document if you will

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and figure out what in the world do we want our script to do.

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And here are the things that we want the script to do and how we want it to operate and what we want

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to look like.

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Well the first thing we decided on was that we want to make sure that this script is called disable

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dash local dash user dot sh.

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Since we're doing some system administration type stuff like deleting users or disabling them we need

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to make sure that whoever is executing this script as root privileges or super user privileges.

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So we're going to put a check for that in the top of our script.

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We also want to provide a usage statement much like you would find in a man page if the user that's

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executing the script does not supply an account name on the command line.

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And then of course we're going to follow good Linux programming conventions and exit our script with

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a non-zero exit status.

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We also decided to use disable as the default action for this script and we also decided that we can

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let the users decide if they want to do something more destructive such as delete an account or remove

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the user's home directory.

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So we've given them a few different options again the dash D will delete an account instead of disabling

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it.

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Nash are you going to remove the home directory and a dash a will create an archive of the home directory

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associated with the account and then store it in the forward slash archive directory.

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Now by the way this is just kind of an arbitrary decision that I made.

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I'm going to put these things in forward slash archives.

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There is no standard for such a directory.

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This is not going to be a directory that you're going to find by default on a newly installed Linux

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system.

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It's not part of the Linux file system hierarchy.

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It's just a folder that I decided to use.

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In that respect what we need to do is just make sure that that directory exists and if it doesn't exist

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we're going to have our script created.

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Now if a user does something interesting like supply an option that we don't account for then we're

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going to give them that usage statement and exit as well.

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We also decided to make it a little bit easier on the end users that are going to be running this script.

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They can supply you know one user to users or however many users they want at the command line so if

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they want to delete seven users well they can supply all seven users at once on the same command line.

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And this script will simply loop through them all and perform the exact same action against all those

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users.

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So if a user supplies the desde option and seven accounts Well it's going to delete all seven of those

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accounts.

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Speaking of deleting accounts we don't want someone to do something interesting like delete the root

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account and make our system unusable.

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Along this logic we don't want to let people who are not system administrators do things like disable

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any system account.

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We know that typically system accounts have a user id less than 1000.

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So let's just put a little check for that in our script and we'll exit saying hey we're not going to

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do that.

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If a system account needs to be deleted we'll give that task over to a system administrator and let

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them do it.

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If we encounter an error along the way either deleting or disabling or archiving the account or creating

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a directory or what have you we're going to tell the user that we encountered a problem and then exit

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the script.

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Also the last thing we want to do is just make sure that we display the user name and any actions that

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we took against that account or username for the user that executed the script.

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So that pretty much does it for our requirements.

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Now let's get to scripting here I have a terminal open on my local system and I'm going to go into the

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shell class folder.

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We're still working on a local user's project and I'm going to bring up the virtual machine and log

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into it.

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Now we'll go into our shared folder of forward slash vagrant.

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And again we decided to name this script disable local user.

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SH

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It goes without saying we're going to supply a shebang line and then we'll just give a comment about

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what the script is going to do.

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So we know that we're going to be executing some commands that require root privileges so let's just

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go ahead and check that right away.

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So if the user ID is not equal to zero then they are not root.

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This is an error message we're going to send this to standard error.

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And then we're going to exit with a non zero exit status.

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We also want to parse the command line options so we'll do that next.

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We know that we can use get ups in a while loop.

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We'll specify our upstream.

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Here are the options that we're going to accept and we're going to accept to delete or to remove Ada

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archive and we'll use the variable option.

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We'll check that option in the case statement here.

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So if someone supplies D.

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Let's set a variable called Delete user and we'll just set that true.

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And then later on in our script we'll check to see if the lead user is true and if it is then well we'll

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delete the user

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here I'm going to do something slightly different.

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If you recall the user del command allows you to specify a dash r option which removes the user's home

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directory.

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So what we're going to do here is use this remove option variable in the user dels statement.

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When we get to that in this script.

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So if this is set to nothing or if the option is never supply this dash our option then remove underscore

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option is going to evaluate to an empty string and nothing will be substituted in its place.

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And so then user data will be executed without this dash our option.

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Now on the other hand if someone does specify Dasch are then the user will be deleted with Dash.

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Now it's going to make total sense when you see it the minute I just want to talk about that for just

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a second.

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We'll do something similar here that we did the delete user option which is if someone gives us a dash

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we'll just check for this archive being true later in the script.

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And if they give us any other option then we're going to tell them how to use our script and exit.

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Now my key statement here is looking pretty nice and compact.

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And I think I'm going to use a function for displaying this usage statement and then exiting the script.

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Now another argument for creating a function like this is that we're going to have to do this same thing

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multiple times in the script because we're going to have some other checks and then we're going to give

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them a usage statement and exit.

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So let's go back to the top of our script here and go ahead and create our function

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as you remember dollar signs zero is always the name of the script not the name of the function like

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you may into it.

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That's not what happens with dollar signs zero it's always the name of the script.

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So we can safely use that in the function.

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So now we have some optional options so those options that are optional go in brackets.

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Then we have a mandatory argument.

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So we're not going to put that in brackets but obviously we have additional users that we can allow

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them to specify and they can specify multiple ones so we'll do this we'll use an ellipsis there.

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Now we're going to exit and that will wrap up our usage function.

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OK let's jump to the bottom of our script.

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And now after we process our options let's shift all those options al the way.

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And then anything that's left over are going to be user accounts and then later we'll loop through those

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user accounts.

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So we want to make sure that the user gives us at least one account to operate against if they don't

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then that means they don't know what they're doing.

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So we're going to give him some help.

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Call our function that we wrote and close our IF statement.

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Now we're ready to loop through all the usernames that were supplied as arguments.

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I like to tell whoever is executing the script what user we're processing or working on.

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Again they may supply multiple users on the command line.

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We want to make sure that we're not removing any system account so we want to get the ID of the user

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that we're processing the Dashiell returned the id the number for a username

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and then we can test against that.

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So if the idea is less than 1000 then we're not going to remove that account.

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Before we do anything like delete a home directory let's make sure we create an archive of it.

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If the user requests us to do that.

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So if someone passed in the dash option then archive gets set to True and if archive is true.

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Well then let's make an archive.

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Actually I'm going to create a variable called archive underscore R which represents the archive directory

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and I'm going to use this multiple times in the script.

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So I think what I'm going to do is put it at the very top of the script even before our first function

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here of usage.

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And really what this is acting as is a constant variable.

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You can even do this you can even make it read only if you like.

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So I'm going put it at the top because this is the only thing that I can think of that we might want

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to adjust later on down the road.

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For example if we want to put these archives on another place in the file system then we can just change

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this variable at the very top of our script make that one small change and not change anything else

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and be good to go.

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OK let's jump back to the bottom and continue scripting.

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So what this statement says is if not exist directory archive directory then.

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OK so how did I get that exclamation point.

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Well you know that the things in double brackets here are tests and you know that we can get information

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on the test.

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We can run by using help test at the command line and if we look at that actually I'll just do that

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now.

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Hope test and it gives us a list of tests and you can see here that exclamation mark expression means

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true if the expression is false so you can think of that as negating the expression or you can think

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of the exclamation point as not.

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So that's where I got that.

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So ultimately what you're saying is if the archive directory doesn't exist.

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Well guess what we need to create it.

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By the way I'm using the dash p option to the make or command because if we have a archived directory

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that has multiple subdirectories for example we can do something like archive users or or whatever.

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And if the first directory the parent directory or parent directories don't exist then we need to create

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them and that's what that Dasch option does to make a command it creates parents if you will.

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So in our particular case we're just using for its slice archive so it doesn't matter.

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But if we were to change that variable at the beginning of our script to something that does include

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subdirectories then we'll need to use a dash piece or kind of future proofing our script if you will

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here.

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So if the make command fails then that's going to mean that we can't put any of the archives you create

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in a directory because a directory didn't exist or wasn't able to be created.

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So we're going to bail on our script here so let's do another check.

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So we'll check the return status of make our

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if it's anything but zero we have a problem.

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So now that we know the archive directory exists let's go ahead and archive the user's home directory

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and move it into that directory.

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Now by default normal user accounts have home directories that live in Fort slash home.

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So if we have adjacent account then my homework is going to be for it slash home for Jason.

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Now if you have an application account or system account that's probably going to live somewhere else

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in the file system.

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For example the route home directory is forward slash R O T an application directory might be for exe

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VAR for s w w w for a web user or something like that.

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So here we're also using this convention to be another safeguard if an account doesn't have a home directory

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and for its last home then it's probably a system or an application account.

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And at that point we probably want a system administrator to look at it manually do it or whatever instead

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of just whoever happens to be managing accounts now those people I'm sure are knowledgeable about managing

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accounts.

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They just may not work on Unix and Linux systems all day like we do.

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So again we're just going to reserve that for a higher level of person that's not using this script.

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On the other hand we could have made the decision that we're just going to extract the proper home directory

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and delete it no matter where it is on disk or create an archive of it no matter where it lives on disk

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so they can leave that up to you.

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But here I'm just going to do it this way.

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So we're going to create an archive file and we're just going to give it a full path here.

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We're going to put it in the archive directory and then we're going to name it user name and we're going

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to make it a compressed tar file so that's going to be t g z.

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Easy for me to say.

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And here we go.

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Here's our check about the home directory.

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So if the home directory does exist then that's a good sign we'll go ahead and move ahead and make our

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archive.

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We're going to compress that so there's a dash z option C to create an archive.

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F is the location of the archive file.

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Then the path to archive which is the home directory and Taar is going to make some noise so we're just

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going to send that to dev null.

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We don't want the user to see any output created by Taar just going to be distracting to them.

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But we do want to make sure that Taar execute successfully

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So if TAR exits with a non-zero exit status we'll say we couldn't create the archive and then exit with

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a non-zero exit status ourselves.

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And the way I just noticed a typing mistake I have a peer.

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I'm used to doing closing bracket and a quotation mark but I don't need that there and if I remove it

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then I see my syntax highlighting go back to normal here.

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And so I notice that because this syntax highlighting look different.

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That's what QBE and to that there.

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So that's kind of good to have an editor with syntax highlighting

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K so this if statement says hey if there is a home directory.

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Daschle if this thing called home Durer is a directory and exists then you archive it.

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And if that doesn't exist or it's not a directory then we're going to tell the user hey that doesn't

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exist or it's not what you think it is we're going to get out of here.

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Exit 1.

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Now this concludes our if archive equals true if statement.

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And now we want to see if we need to delete the user or not.

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So let's do this

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so here is what I was talking about earlier with this remove option.

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So if we're going to delete a user we need to use the user del command.

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Additionally if we want to delete the user's home directory We need the dash our option.

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So if they give us a dash or option we store that and remove underscore option.

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Now here remove underscore option will evaluate to dash or if they supply Dasch are or it will evaluate

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to an empty string.

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In that case it just going to be like user space space user name which is going to give us the exact

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result that we want.

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So that is one way to handle this kind of situation.

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There are other ways but this is a pretty simple way to do this.

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So we want to check the exit status of the user Dell command because we don't want the user thinking

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that an account got deleted when it really didn't get deleted.

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Now I want to point out something here we're doing a lot of the same thing here which is checking for

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an exit status if it's not zero then we're going to give an error message an exit.

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So I'm doing each one explicitly and changing the echo statement for each one so that the user knows

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exactly what failed in the script.

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In theory you could simplify this a bit and say Write a function that well executed command and then

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check the return status on that command and then bail or exit your script.

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If it doesn't succeed.

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So there is some food for thought or maybe that some extra credit after you write the script this way

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then maybe write a script and have it use a function called a run command or run in check or something

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like that.

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Just something to keep in mind

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if we make it past the if statement that means the account was deleted and by the way here's another

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thing you could have put this inside of the if statement like this you could have said if there was

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a non-zero exit says we have a problem get out of here or if there was not not not zero.

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If they exist that's one zero more or less than the account was deleted.

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I'll leave that up to you.

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I'm just going to do it this way if it makes it past that if statement then the account was deleted.

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That makes sense in my mind.

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So if the delete user is set to true we do all that above we use user Dell.

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If it's not set to true then we're just going to disable the account or expire at I can do that with

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a S.H. age command.

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And again we're just going to actually duplicate this bit of code so I'm just going to copy it and paste

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it and just change it.

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Here it says the account user name was not disabled.

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Again if you're copying and pasting that may be a sign you need a function

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and go ahead and grab these two lines appear as well.

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Again if we get past this if statement that means the account was disabled

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that brings us to the end of that if statement.

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That also brings us to the end of our For loop and that also brings us to the very end of our script.

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We are going to exit with a zero exit status.

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Now I know with long scripts like this I can make some mistakes.

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And also one of the most common mistakes are typing mistakes not necessarily logic mistakes.

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So I'm going to do is actually go back to the very beginning of this script and look for things like

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quotation marks spelling mistakes brackets braces kind of some normal hot spots that I may have some

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errors and some is going to jump back to the top and just kind of read things through and correct them

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as I see them.

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OK.

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The first here I see the script we can call it this script that's a minor one and a comment not going

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to make a difference to functionality but there's a little typing mistake.

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Here's another one.

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Here's another one I have a dollar sign in the wrong place.

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We go inside the quotes there as you can see can you see the syntax highlighting change so that's good.

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That's another area that I found here.

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OK at least I found a couple and corrected them before I executed my script.

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If not then I would have just started debugging then maybe the error message would have given me an

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indication of where at.

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In the script I had the air and so on.

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I would have also perhaps gone to the very top here and you some options like Dash X Daschle or dash

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VI or even all three combined there to do some debugging that way or even some manual debugging like

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this.

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I would just echo archived deicer and then exit for example to create a manual stop point or checkpoint

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if you will.

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So those are just a couple of debugging tips now that we have our script created before we execute it.

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We need to give it executable permissions.

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Now let's execute this script without super user privileges and see what happens.

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Says Please run with seducers route.

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That's what we want.

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Let's make sure it exited with a non-zero exit status.

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And sure enough we have an exit status of one.

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So this time let's run it with the proper privileges but don't supply any options or don't supply any

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usernames.

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OK we get a usage statement just like we wanted.

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And we also get a non-zero exit status which is exactly what we expect now that supply an invalid option.

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Let's apply a dash Z which we don't do.

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And it says disable local user illegal option dashes Z.

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Now that is coming from the get shell built in.

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But the usage statement of course is coming from our usage function.

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Since we know that that function ends with exit one we can confirm that indeed our script exited with

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a 1 exit status.

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Now it's trying to disable a system account.

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So on these particular systems we're not really using mail and no mail is a system account user with

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a low I.D..

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So let's go ahead and delete that.

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Now if we the leader the mail account and probably nothing bad is going to happen.

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And again these are test systems so we could throw them away and build a new one.

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So let's try it here to disable local user and we'll try to disable the mail user.

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It says I'm refusing to remove the mail account that has a huge ID of 8.

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So that is exactly what we want.

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Again a nonzero exit status to go with that.

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So now what I'm going to do is actually create some test accounts here to test my script with an actually

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wrote a script to create these test accounts.

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I'll just show it to you really quick here.

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It's a pretty simple script.

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It just is mainly a for loop that sets everybody's password.

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Yes.

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One two three creates the count and then sets the password so I'll go ahead and add those test accounts

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now.

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And now we have a few accounts to play with.

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Now let's run our script against one of these test users that we created.

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Here it says the account was disabled.

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So let's make sure it's disabled by trying to log into it.

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We'll use our handy password of pass 2:59.

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And it says your account has expired please contact your system administrator.

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So that's the exact kind of behavior we want just to be thorough.

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Let's also make sure that the home directory for that user still exists.

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Sure enough it does.

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No it still leaves the mark h account.

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So we'll give our script here we need the dash D for the delete option and then the account of Mark

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H.

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It says processing user and the account was deleted.

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Let's see if it was say no such user that means it's gone

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pay the home directory still exists which is the behavior we wanted and expected.

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Now let's the lead a user and their associated home directory so we can do dash d r k it says the user

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was deleted.

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That's right.

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OK home directory is gone.

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OK now let's test the functionality that we have built into our script of operating on multiple users

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that are supplied as arguments to the script.

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And also let's test the ability to create archives of these user accounts.

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So let's do this.

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We'll use Dashti for delete or to remove their home directory and archive it before it gets removed

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and we'll give them these two users.

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OK.

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It says processing user Alyque G creating directory forward slash archive.

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Now that is the directory that we're going to store these archive files in.

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And again that doesn't come by default on a Linux system.

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So we had to create it herself in our script and it says it's archiving the whole Mallik directory to

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archive good PDZ.

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And then it says the account was deleted and then it moves on to the next account.

347
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Peter archive and delete as well.

348
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So let's make sure the accounts and home directories are gone.

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The account is gone.

350
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For Peter M. has also gone.

351
00:32:00,030 --> 00:32:02,360
Just check these both at once here.

352
00:32:04,850 --> 00:32:11,670
Hey no home directories but let's make sure the archives were in fact created.

353
00:32:11,680 --> 00:32:13,700
Hey there we have to.

354
00:32:14,190 --> 00:32:16,790
The files one for each account.

355
00:32:17,170 --> 00:32:19,790
Let's look at the contents of those archives.

356
00:32:20,180 --> 00:32:22,160
Compress only to dash Z.

357
00:32:22,240 --> 00:32:23,660
T to list the contents.

358
00:32:23,660 --> 00:32:25,310
The will be verbose.

359
00:32:25,340 --> 00:32:29,080
F allows us to specify the file.

360
00:32:29,180 --> 00:32:31,760
This one first that looks good.

361
00:32:36,770 --> 00:32:41,090
OK and we have the archive of both of those accounts.

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So that wraps it up for this particular exercise.