Introduction to bash shell scripting (20090307 classroom)

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I put together StabbyMc's_Intro_to_Shell_Scripting to organize the ideas in a more linear fashion. I also added some additional concepts that we weren't able to get to in class.

IRC Log

-!- nirik changed the topic of #fedora-classroom to: Fedora IRC Classroom - Introduction to bash shell scripting with your teacher Scott McBrien (		11:15
StabbyMc_ ) - See Classroom for class schedule today and more info.
StabbyMc_	OK, it's 18:15 UTC, lets get started	11:15
oNe3	ok	11:15
StabbyMc_	Questions are welcome	11:15
wonderer|chatzil	ok	11:15
@nirik	ok, take it away StabbyMc_ !	11:15
StabbyMc_	I'd like to keep comentary to a minimum ;-)	11:15
StabbyMc_	Alright, so we're talking about an introduction to shell scripting.	11:15
zer0c00l	damn squid will go down shortly for a log backup :(	11:15
oNe3	<nirik> ok	11:15
StabbyMc_	And the example I've put together is adding a user to a machine.	11:15
StabbyMc_	So when you're adding a user to a machine, what do you typically do?	11:16
StabbyMc_	What commands would you run?	11:16
linuxguru	useradd , passwd	11:16
StabbyMc_	exactly.	11:16
oNe3	cd mkdir	11:16
oNe3	cat tail	11:16
oNe3	ls	11:16
oNe3	sh	11:16
@nirik	oNe3: uh, those seem unrelated to adding a user. ;)	11:16
StabbyMc_	You use useradd to add the user to /etc/passwd, /etc/shadow, create and populate their home dir...	11:17
StabbyMc_	Then you need to set their inital password with passwd.	11:17
oNe3	service ... status	11:17
StabbyMc_	So two separate commands that you almost always have to run together to accompish the task of adding a user.	11:17
StabbyMc_	*THIS* concept is the beginning of a shell script.	11:17
StabbyMc_	At its most basic core, a shell script is simply a list of commands to run in order.	11:18
StabbyMc_	If you're familiar with some _other_ operating system, at a very basic stage a shell script is like a batch file.	11:18
StabbyMc_	So I've written some examples for us to take a look at.	11:19
StabbyMc_	The first is very basic.	11:19
StabbyMc_	http://fpaste.org/paste/4852	11:19
StabbyMc_	So to make this script, I added the two commands that I need to run to add a user to a file.	11:19
StabbyMc_	Then I make the file executable, by something like chmod +x <name of file>	11:20
StabbyMc_	And lastly, to invoke the script with these two commands, on the command line I provide the full path to the file I've created.	11:20
StabbyMc_	Or if I'm in the directory that contains the file I can run ./script_file_name	11:20
StabbyMc_	-OR-	11:20
StabbyMc_	What I think is the best mechanism, on Fedora the PATH variable includes ~/bin	11:21
rtnpro	StabbyMc_: !	11:21
StabbyMc_	So I generally take the executable file and drop it in /root/bin so that I can just run it like a command on the command line.	11:21
StabbyMc_	Ok, so to recap, I put the commands I want to run in a file, make the file executable, then call it from the command line.	11:22
@nirik	rtnpro: you had a question? go ahead and ask...	11:23
StabbyMc_	Before we start talking about making changes to the contents of the script, making it more sophisticated, any questions on how we execute	11:23
a basic script?
StabbyMc_	yes, please post questions as you have them, no need to be recognized.	11:23
oNe3	in the begin of file with +x need string #/bin/sh/?	11:23
StabbyMc_	oNe3: an excellent question.	11:24
rtnpro	StabbyMc_: will it work without the #!/usr/bin/sh	11:24
StabbyMc_	That will be one of the first enhancements to our script.	11:24
oNe3	yes	11:24
StabbyMc_	Without the #! line, a shell script will assume that you wish to use the shell program that the user has.	11:24
oNe3	this only identify script	11:24
StabbyMc_	So for many of us this is the bash shell.	11:24
oNe3	# is commentary	11:25
mahesh	can i execute a file being in the same directory and by using the command $bash <filename>	11:25
StabbyMc_	So if I run the script, it will be interpreted as a bash script.	11:25
rtnpro	ok	11:25
StabbyMc_	mahesh: yes you can also do that.	11:25
oNe3	perl will run witout :)	11:25
oNe3	without	11:25
mahesh	StabbyMc_ ok	11:26
StabbyMc_	Alright, I think we're all thinking in the same direction, so lets take a look at a slightly more enhanced version of the same script..	11:26
StabbyMc_	http://fpaste.org/paste/4853	11:26
StabbyMc_	So notice in this version I added the #! at the top.	11:26
oNe3	StabbyMc_, create users is the litle problem on desctop, and many usefus servers have a virtual users stored in DB	11:27
StabbyMc_	The reason you want to do this is what happens if someone running the script uses pdksh or tcsh as their shell? The commands will be run	11:27
with the wrong shell interpreter.
StabbyMc_	So the #! at the very top tells us what program to call to read and execute the commands contained in this script.	11:27
StabbyMc_	oNe3: we'll be addressing that :-)	11:28
oNe3	yes, its right	11:28
franciscod	StabbyMc_: scripting isnt the same for them is it ?	11:28
StabbyMc_	The #! is also something that you see in perl scripts for the same reason.	11:28
franciscod	for pdksh etc ?	11:28
StabbyMc_	You don't want your perl program instructions read and executed by bash, which uses very different syntax	11:28
StabbyMc_	franciscod: right.	11:28
StabbyMc_	now at the bottom of the script we see a line that begins with #	11:29
oNe3	where? in perl or bash?	11:29
StabbyMc_	Except for the first line in the script which is a # followed by a !, any other occurence of # will be seen as a comment.	11:29
StabbyMc_	oNe3: for #! lines, it works the same in both schell scripting and perl. Generally that's true of any interpreted (non compiled) language.	11:30
Zart	it's possible to run the same script via bash/perl/tcl with some syntax tricks	11:30
oNe3	script language	11:30
oNe3	like perl and bash	11:30
StabbyMc_	So the line down at the bottom of the script is a comment, and I've added a bit to tell us how this program should be executed on the	11:30
command line.
StabbyMc_	(we'll be changing this too to make it better, later)	11:30
oNe3	)	11:31
StabbyMc_	In addition to adding the interpreter to use (#!) and the comment, I've also made one other change.	11:31
StabbyMc_	in the previous example, my script added a single user, frank.	11:31
StabbyMc_	which means in order to re-use it, I'd have to edit the file and change the username.	11:31
oNe3	StabbyMc_, please put scripts here	11:32
StabbyMc_	Which is a lot of work, and the point of scripting is to do less work!	11:32
StabbyMc_	http://fpaste.org/paste/4853	11:32
StabbyMc_	oNe3: this is the script I'm talking about currently.	11:32
StabbyMc_	The additional change I've made is adding a variable, $1	11:32
StabbyMc_	notice that I now useradd $1	11:32
StabbyMc_	and set the password for $1	11:32
StabbyMc_	$1 is known as a positional parameter	11:33
StabbyMc_	meaning it's value corresponds to the 1st argument passed to the script as an argument.	11:33
franciscod	StabbyMc_: is there a $0 ? coressponding to the app name ?	11:34
StabbyMc_	positional parameters start at $0 (the script name) and will be assigned for as many items are passed to the script on the command line.	11:34
franciscod	answered.. thanks..	11:34
StabbyMc_	franciscod: we're on the same page ;-)	11:34
franciscod	:)	11:34
StabbyMc_	So now, as the comment at the bottom of the page indicates, when we call the script it'll look something like	11:34
StabbyMc_	scriptfile frank	11:34
StabbyMc_	$0 will be assigned as "scriptfile" and $1 is frank	11:35
oNe3	./frank ?	11:35
StabbyMc_	Later we'll be enhancing the script to handle multiple users.	11:35
StabbyMc_	oNe3: no, more like ./useradd-wrapper frank	11:35
StabbyMc_	so the command we're running corresponds to the file that our scripted commands are stored in.	11:36
oNe3	how to edit more than 1 users?	11:36
StabbyMc_	So we could ./useradd-wrapper frank vlad amelia	11:36
oNe3	stored in /usr/bin	11:36
StabbyMc_	where frank would be $1, vlad is $2, and amelia is $3	11:36
* franciscod gets this part properly..		11:37
StabbyMc_	But currently the *internals* of our script doesn't support multiple users.	11:37
StabbyMc_	we'll be updating it though.	11:37
zer0c00l	yeah	11:37
StabbyMc_	So my idea for this lesson is that we start with something very basic and keep enhancing the same script to make it better.	11:37
StabbyMc_	to make it handle more than one user.	11:37
StabbyMc_	to add more customization for adding users.	11:38
wonderer|chatzil	sounds good.	11:38
zer0c00l	StabbyMc_: why that --stdin why not "passwd $1"	11:38
StabbyMc_	So lets say that these commands are in a file /root/bin/useradd-wrapper	11:38
StabbyMc_	zer0c001: Ah a great question.	11:38
oNe3	is learning pass for $1 username )))	11:39
StabbyMc_	so the problem with passwd is, that by default, it's interactive.	11:39
oNe3	)	11:39
StabbyMc_	If we just run passwd $1 it will now require us, the admin, to type in the password, then type it again to set it.	11:39
oNe3	many interactive commands in linux )))	11:39
StabbyMc_	I'm using the --stdin option to passwd so that passwd will accept the user's password over a |, rather than ask me to type it.	11:40
* franciscod looks at "man passwd"		11:40
oNe3	| is the system conveer	11:40
StabbyMc_	so in the script as it is, I'm setting the username in $1's password to be the string, mypassword.	11:41
StabbyMc_	So if we call useradd-wrapper frank	11:41
franciscod	*--stdin* This option is used to indicate that passwd should read the new password from standard input, which can be a pipe.	11:41
StabbyMc_	frank is added, and has a password of mypassword	11:41
StabbyMc_	if we useradd-wrapper vlad	11:41
StabbyMc_	vlad is created and also has a password set of mypassword	11:41
StabbyMc_	This makes you all unhappy right? That everyone gets the same password?	11:42
oNe3	typing passwords in scripts are bad	11:42
StabbyMc_	oNe3 I agree.	11:42
StabbyMc_	So that's our next enhancement.	11:42
StabbyMc_	But before we move to that, I want to make sure everyone is OK with $1 and the idea of positional variables.	11:43
StabbyMc_	Questions?	11:43
* franciscod is okay with position variables..		11:43
franciscod	StabbyMc_: any limit to number of posn variables ?	11:43
oNe3	#	11:43
oNe3	echo mypassword | passwd --stdin $1 .... password is mypassword or -stdin $1 ?	11:43
* sherry151 understood too.		11:43
SSlater	What if the system already has a frank?	11:43
StabbyMc_	oNe3: the password set for the user in $1 is whatever string passed by echo.	11:44
rtnpro	oNe3: I didn't get the 2nd step	11:44
StabbyMc_	so echo mypassword sets the password for the user $1 to be mypassword	11:44
StabbyMc_	If we echo "supersecret" | passwd --stdin $1	11:44
rtnpro	oNe3: ok	11:44
mahesh	$0 is script file... iam not clear with this	11:44
oNe3	but mypassword | is not variable!!!	11:44
StabbyMc_	now the user we add has a password of supersecret	11:45
StabbyMc_	oNe3: Not yet.	11:45
oNe3	$mypassword maybe?	11:45
StabbyMc_	But remember, we're starting small, and fixing things as we go!	11:45
Zart	short summary: scripts allow execution of number of commands and allow re-using them later for various tasks. to make them more flexible, we're	11:45
using arguments to parametrize them
StabbyMc_	Zart: right on.	11:45
StabbyMc_	Lets take a look at a new enhancement.	11:46
StabbyMc_	http://fpaste.org/paste/4854	11:46
zer0c00l	i have another question passwd command will ask us two times password right? how could our script do it?	11:46
StabbyMc_	zer0c001: that's why I'm using --stdin, so that the passwd command doesn't require me to type anything, it takes input over the |.	11:46
zer0c00l	ok	11:46
oNe3	http://fpaste.org/paste/4854 hm	11:47
StabbyMc_	Ok, so the new enhancement takes care of some of our issues.	11:47
StabbyMc_	2 new things are added.	11:47
oNe3	#	11:47
oNe3	#!/bin/bash	11:47
oNe3	#	11:47
oNe3	#	11:47
oNe3	useradd $1	11:47
oNe3	#	11:47
oNe3	#	11:47
StabbyMc_	First, we have a variable to store the password!	11:47
oNe3	password=mkpasswd	11:47
oNe3	#	11:47
heftig	i suppose mkpasswd is another script	11:47
oNe3	#	11:47
oNe3	echo $password | passwd --stdin $1	11:47
StabbyMc_	oNe3	11:47
@nirik	oNe3: don't paste entire scripts please... use pastebin. ;)	11:47
oNe3	ok	11:47
StabbyMc_	We can't paste the contents of the script in chat, which is why I'm putting up the links to them :-)	11:47
oNe3	ok, sorry	11:48
StabbyMc_	so we're creating a new variable called password	11:48
StabbyMc_	Which we use later in our passwd command.	11:48
oNe3	but what is password=mkpasswd ?	11:48
StabbyMc_	So that now we don't have the same password being set for everyone.	11:48
StabbyMc_	oNe3 sees the other change.	11:48
StabbyMc_	So I could have done something like	11:49
oNe3	ok	11:49
StabbyMc_	password="mypassword"	11:49
StabbyMc_	but that would still end up setting every new user's password to the same string :-(	11:49
oNe3		11:49
linuxguru	oNe3, read this when you get time http://fedoraproject.org/wiki/Communicate/IRC/Maximizing_Support_from_IRC	11:49
StabbyMc_	AND I'd still have the password in plain text in this file.	11:49
StabbyMc_	so oNe3 is right.	11:49
StabbyMc_	mkpasswd is another command.	11:49
StabbyMc_	if you run it on your machines and it says "mkpasswd Command not found"	11:50
zer0c00l	ya	11:50
StabbyMc_	That's because this program is provided by the expect RPM	11:50
StabbyMc_	so if you yum install expect	11:50
StabbyMc_	You'll get mkpasswd installed (as well as the expect programming language)	11:50
oNe3	<linuxguru> i know this, i want to speak, if you think bad for me say this and i.m be banned	11:50
StabbyMc_	mkpasswd is a program that will create random 8 character passwords	11:51
StabbyMc_	The 8 characters will include a mixture of upper and lower case, digits, and an other character.	11:51
franciscod	StabbyMc_: how will we know what it generated?	11:51
StabbyMc_	franciscod: well that's a problem.	11:51
StabbyMc_	Because it really is RANDOM	11:51
zer0c00l	:-)	11:52
StabbyMc_	So we'll be fixing that too, but it'll be later.	11:52
linuxguru	franciscod, you can echo $password	11:52
franciscod	so we've made accounts and we dont know the passwd? ;)	11:52
StabbyMc_	For right now, yes.	11:52
StabbyMc_	But in real life, that would be silly. Especially since we can't tell the new user what their password is because its a random string!	11:52
StabbyMc_	But again, we'll be fixing that. Its towards the end though.	11:53
mahesh	can we view those random passwd's later	11:53
StabbyMc_	for now, lets just say "Yea we get randomized passwords, hurrah"...	11:53
StabbyMc_	mahesh: not unless we store them.	11:53
StabbyMc_	once the script ends, the value in $password will be lost.	11:53
StabbyMc_	Oddly enough, we'll be storing them later ;-)	11:54
mahesh	StabbyMc_ ok	11:54
StabbyMc_	The bigger concept to take from this is not mkpasswd, but rather how we're calling it in the script.	11:54
StabbyMc_	Notice that we're setting the variable to mkpasswd	11:54
linuxguru	command substitution	11:54
StabbyMc_	This is a concept known as command substitution or quoted execution.	11:54
StabbyMc_	the charcter	11:55
StabbyMc_	is the backquote.	11:55
StabbyMc_	it shares the key with the ~ character on US keyboards. If you were to use a single quote ', it would not work right.	11:55
zer0c00l	ok	11:55
StabbyMc_	Now for almost all the additional examples I use s to do my quoted execution.	11:56
StabbyMc_	But there is another way you may see it, or you may prefer to have quoted execution in your scripts.	11:56
StabbyMc_	http://fpaste.org/paste/4855http://fpaste.org/paste/4855	11:57
StabbyMc_	http://fpaste.org/paste/4855	11:57
StabbyMc_	http://fpaste.org/paste/4855	11:57
StabbyMc_	Bah	11:57
StabbyMc_	Ok, laggy network, sorry about htat.	11:57
linuxguru	no problem	11:57
linuxguru	ok so i thought $(mkpasswd) will fork a new sub-shell and mkpasswd will not	11:58
* nirik thinks they are the same thing, both do a subshell and pass the output back. Just a matter of quoting differences.		11:59
heftig	uh, as far as i can determine both fork a subshell	12:00
* nirik nods.		12:00
linuxguru	okay	12:00
* nirik suspects StabbyMc_ is renewing his network connection. Should be back in a sec here.		12:00
delhage	did scott lose his connection now?	12:00
StabbyMc_	so we can also take the output of a command and store it in a variable by the method here	12:00
StabbyMc_	Using $(command)	12:00
StabbyMc_	Which according to delhage is easier if you're not using a US keyboard.	12:00
StabbyMc_	So right now, we have a basic script that adds a user (passed on the command line) and sets their password to a random string.	12:00
StabbyMc_	questions on quoted execution or setting variables in a script?	12:00
StabbyMc_	Ok, so one of the questions asked earlier was what if user $1 already exists.	12:01
StabbyMc_	Right now we'd change their password to a random string and see an error out of useradd that the user already exists.	12:01
StabbyMc_	So lets enhance the script further to make it a little more tolerant of errors.	12:01
StabbyMc_	http://fpaste.org/paste/4856	12:01
StabbyMc_	Yeah, I'm back...	12:01
StabbyMc_	linuxguru, they both fork a new shell for the quoted command.	12:01
StabbyMc_	if you don't want a subshell created, take a look at the source command.	12:01
StabbyMc_	also known as the . command	12:01
linuxguru	StabbyMc_, thanks	12:01
StabbyMc_	So this script http://fpaste.org/paste/4856	12:02
StabbyMc_	introduces the if statement	12:02
StabbyMc_	Lets check a condition on the machine before proceeding.	12:02
StabbyMc_	Now an if is a shell command, just like echo or others.	12:02
StabbyMc_	it takes an argument of a command to run.	12:02
StabbyMc_	And it will check the return of that command to see if the command is successful or failed.	12:03
StabbyMc_	So lets fill in this condition.	12:03
mahesh	what does fi do??	12:03
StabbyMc_	http://fpaste.org/paste/4857	12:03
StabbyMc_	mahesh: you may have worked with other programming languages where code is put in blocks?	12:03
StabbyMc_	Usually with some kind of bracket character, well in shell a fi is the command that ends an if command block	12:04
franciscod	it closes the block..	12:04
mahesh	StabbyMc_ ok	12:04
StabbyMc_	You'll see this kind of thing with several other shell control constructs.	12:04
StabbyMc_	In a minute or so we'll talk about for loops.	12:04
StabbyMc_	They'll have some keywords that define their code blocks too.	12:05
mahesh	StabbyMc_ ok	12:05
StabbyMc_	Sometimes, like with if, it's the word spelled backwards.	12:05
StabbyMc_	Or with a case statement, you'd end it with an esac (case spelled backwards)	12:05
StabbyMc_	With loops it is usually do and done that define the loop contents.	12:05
StabbyMc_	So with script http://fpaste.org/paste/4857	12:06
mahesh	StabbyMc_ clear now	12:06
StabbyMc_	we're running useradd $1 as an argument to if.	12:06
StabbyMc_	which means if the useradd is successful, we will then set the user's password.	12:06
StabbyMc_	But if the useradd fails (maybe because the user already exists) we skip the code in the then-fi code block.	12:06
StabbyMc_	We'll be doing some more with if statements in a bit, and there are some neat things you can check beside trying to run a command.	12:07
StabbyMc_	So this is how we can check to make sure we don't mangle existing users on the system with our script.	12:08
StabbyMc_	I'll be making it a little better soon.	12:08
StabbyMc_	But one of the early other problems that was raised is working on multiple users.	12:08
itnomad	if useradd fails, will we see the error in the output?	12:08
heftig	itnomad: yes	12:08
itnomad	thanks	12:08
StabbyMc_	itnomad: yes, but I'll address that too.	12:08
StabbyMc_	http://fpaste.org/paste/4859	12:09
StabbyMc_	So this is the syntax of adding a for loop.	12:09
StabbyMc_	In shell, for is an iterative loop that will execute the contents of the do-done code block until the list of items it's been passed has	12:09
been exhausted.
StabbyMc_	for each iteration, the placeholder variable contents are replaced with the current item we are iterating on.	12:10
StabbyMc_	So filling in these pieces...	12:10
StabbyMc_	http://fpaste.org/paste/4860	12:11
StabbyMc_	http://fpaste.org/paste/4860	12:11
StabbyMc_	So now our script can accept up to 5 usernames on the command line	12:11
StabbyMc_	but if we only provide 2 users, it'll produce some errors.	12:11
StabbyMc_	So instead of using $1 - $5	12:12
heftig	would it try to add some users with an empty name?	12:12
StabbyMc_	lets replace that with a copy of EVERYTHING passed to the script on the command line.	12:12
StabbyMc_	heftig: if you just run useradd with no arguments, it'll error.	12:12
heftig	StabbyMc_: right	12:12
delhage	!	12:13
StabbyMc_	So just like $1 was set up automatically when the script runs.	12:13
StabbyMc_	There is another variable $* that get's set up.	12:13
StabbyMc_	delhage, question away.	12:13
StabbyMc_	$* is a variable that contains a copy of ALL arguements passed on the command line.	12:13
StabbyMc_	So if we call useradd-wrapper frank vlad joe	12:14
delhage	I just want to point out that if $4 and $5 aren't set they will not be included in the for loop	12:14
StabbyMc_	$* contains "frank vlad joe"	12:14
delhage	so no error	12:14
StabbyMc_	thanks for that clarification delhage :-)	12:14
heftig	woohoo	12:14
StabbyMc_	if the script is called useradd-wrapper frank joe vlad amelia foobar	12:14
StabbyMc_	then $* contains "frank joe vlad amelia foobar"	12:14
StabbyMc_	A copy of all the arguments passed to the script.	12:15
StabbyMc_	So better, and more flexible would be: http://fpaste.org/paste/4861	12:15
StabbyMc_	So for each argument stored in $*, we're going to iterate over the contents of the for loop's do-done code.	12:16
StabbyMc_	And each time we do an iteration, the current item we're working on from $* is going to be stored in the placeholder variable $user	12:16
* nirik notes we are at 19:15 UTC now. ;) Feel free to go over, but do provide some break time before the next class. ;)		12:16
StabbyMc_	nirik, thanks, I should be able to wrap up in another 5-10 mins :-)	12:16
StabbyMc_	I think right now we have a pretty good script.	12:17
StabbyMc_	It works with a variety of things passed as parameters.	12:17
StabbyMc_	But we need to make it more error tolerant.	12:17
vinod	also we can use $@ in place of $*	12:17
StabbyMc_	what happens when you call it and pass no users?	12:17
mahesh	StabbyMc_ ok	12:17
mahesh	errors	12:18
StabbyMc_	http://fpaste.org/paste/5352	12:18
StabbyMc_	So I've added a new if statemetn into the mix.	12:18
StabbyMc_	And I've added a new branch to the if statement.	12:18
StabbyMc_	An else.	12:18
franciscod	[ ] -> test .. right ?	12:18
StabbyMc_	the command we're running in the if is a test	12:19
StabbyMc_	franciscod: right!	12:19
StabbyMc_	so there is a command called test.	12:19
StabbyMc_	or it's often abreviated with this [ condition ] syntax	12:19
StabbyMc_	bash includes a variety of things that you can verify in a test command.	12:19
StabbyMc_	I'm using -n	12:19
StabbyMc_	-n checks to see if it's argument is a non-zero lenght string.	12:20
* nirik notes there is a [ binary that is really the test command. ;)		12:20
zer0c00l	yeah	12:20
StabbyMc_	So if you don't pass any arguments, $* is empty, and is therefore a zero lenght string.	12:20
herlo	$ which [	12:20
StabbyMc_	which would fail the if check.	12:20
herlo	/usr/bin/[	12:20
StabbyMc_	and would launch us into the else branch.	12:21
StabbyMc_	So only if arguments are passed, ie $* has content, will we try and iterate though the arguments using a for loop.	12:21
delhage	[root@mccloud ~]# type [	12:21
delhage	[ is a shell builtin	12:21
StabbyMc_	If the script is called with no arguments, we fail the if test and go into the else	12:21
StabbyMc_	which echos out an error message	12:21
@nirik	delhage: it's that too. :)	12:21
* franciscod directs to http://www.freeos.com/guides/lsst/ch03sec02.html		12:22
StabbyMc_	Adn sets an exit value.	12:22
zer0c00l	what is a exit value? why 7 there?	12:22
zer0c00l	*an exit	12:22
StabbyMc_	Ok last change we have time for, I'll post the rest of the unit on the wiki to go along with the log.	12:22
StabbyMc_	http://fpaste.org/paste/5353	12:22
StabbyMc_	I also added an else statement to our sucessful useradd check.	12:23
StabbyMc_	So if useradd is unsuccessful, it errors about that person, but will continue to try and add additional users on the commandline.	12:23
StabbyMc_	zer0c001: the seven is a non-zero value.	12:24
StabbyMc_	When commands exit successfully, they return a 0.	12:24
heftig	wouldn't that output two errors? one from useradd to stderr and one from the script to stdout	12:24
StabbyMc_	On unsuccessful exit, they return non-zero	12:24
StabbyMc_	heftig: yes it would.	12:24
StabbyMc_	In the next changes I make, I redirect errors and output from things like useradd and passwd to /dev/null	12:24
StabbyMc_	That way we only see output from the scripts that WE put in, rather than random command crud.	12:25
StabbyMc_	Ok, but I think that's all we have time for... I'll update the wiki, and maybe we'll finish the last bits in another class.	12:25
@nirik	thanks for the class StabbyMc_ !	12:25
neverho0d	StabbyMc_: we should add some commands for password storage, so we will be know what password users get after the scripts finished	12:25
franciscod	StabbyMc_: thanks :D	12:26
mahesh	StabbyMc_ thankyou	12:26
-!- nirik changed the topic of #fedora-classroom to: Fedora IRC Classroom - Next class at 19:30UTC - See Classroom for		12:26
class schedule today and more info.
SSlater	Thanks StabbyMc_	12:26
zer0c00l	thank u very much for the wonder full class StabbyMc_	12:26
baconfork	where on the wiki will the rest of it be?	12:26
StabbyMc_	neverho0d: I've got that too, and mailing the information to the user as well ;-)_	12:26
neverho0d	StabbyMc_: ok. thank you very much!	12:26
itnomad	Thanks StabbyMc_ it would be cool if you could suggest some exercises.	12:26
StabbyMc_	baconfork, I'll add it to the transcript page, or at least a link to it from the transcript page when inode0 gets it up.	12:26
linuxguru	StabbyMc_, nice. hope to see you in the next bash class for advanced users	12:27
* wonderer|chatzil also thnaks for the class.		12:27
StabbyMc_	If you guys want another more advanced class, suggest it on the classroom wiki page :-)	12:27
heftig	StabbyMc_: ty	12:27
baconfork	StabbyMc: Thanks for the class	12:27
StabbyMc_	You're all welcome, sorry we ran out of time :-)	12:27

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