Simple script for adding groups to Linux

kenji1903 · 05-27-2004, 05:14 AM

Howdy!

I am trying to write a script for adding groups and users for my samba domain... Here is what I have tried writing, I have not started on the user part since I cannot get the groups to work properly:

Code:

#!bin/bash

echo -n "Enter group name: "
read group_name

#checks to see if group is already added to /etc/group 
if [ "$group_name" == "grep '$group_name' /etc/group" ]; then
    echo "Group already exists! Skipping group creation..."
    exit 1
else
    /usr/sbin/groupadd $group_name
    echo "Group added"
fi

Output:
# sh grouptest.sh
Enter group name: test
Group added

#sh grouptest.sh
Enter group name: test
groupadd: group test exists
Group added

Seem to me the the portion just below the if statement is entirely ignored... Why is that?
I have programming basics, just not good at it thats all

Cheerio~!

Oliv' · 05-27-2004, 10:24 AM

Hello,

It seems that your IF statement is always wrong even if the group already exists

For example, if you type:

Code:

grep root /etc/group
root:x:0:

the result is the whole line with hidden password and GID... so to correct it either you use a "|cut" extension to have only group name or you find another way like:

Code:

if [$(grep $group_name $group_file | wc -l) -eq 1]

Hope this help you

Oliv'

keefaz · 05-27-2004, 10:42 AM

Well it won't work if an user has the same name of a group for example.
I would do :

Code:

group_test=$(cat /etc/group | awk -F: '{ print $1 }' | grep $group_name)

if [ -z $group_test ]; then
    -- add the group
else
     -- print group exist
fi

Oliv' · 05-27-2004, 10:52 AM

Yes, you're right keefaz

But it was only an example... a wrong one

But the solution with the "cut" command is good as you tell the script to keep the first word of the line

Code:

grep $group_name $group_file | cut -d: -f1

Oliv'

keefaz · 05-27-2004, 11:06 AM

We are false. Try with a group named "roo"

so I revisit my example

Code:

group_test=$(cat /etc/group | awk -F: '{ print $1 }' | grep $group_name)

if [ -z $group_test ] || [ ! "$group_test" = "$group_name" ]; then
    -- add the group
else
     -- print group exist
fi

kenji1903 · 05-27-2004, 06:49 PM

I'm not exactly sure what you 2 experts are writing... but it works!!

Thanks a million~!

I spent the whole day looking at scpriting websites but i'm still in the dark about all these: ' " ` { [ (

OK, now time for me to understand what all those terms mean in the code... do I look at man bash?

Any websites that you think would be good for a beginnner?

Thanks again keefaz and Oliv'

chEErs,
~WiLL~

320mb · 05-27-2004, 07:08 PM

http://www.ss64.com/bash/

kenji1903 · 05-27-2004, 09:15 PM

Quote:

We are false. Try with a group named "roo" so I revisit my example

Code:

group_test=$(cat /etc/group | awk -F: '{ print $1 }' | grep $group_name)

if [ -z $group_test ] || [ ! "$group_test" = "$group_name" ]; then
    -- add the group
else
    -- print group exist
fi

OK... let me confirm a few things:
- The commands inside $(...|...|...) greps the first column (before the first colon) of /etc/group which matches the entered group_name, right? then assigns the value to group_test...
- then the first if condition checks if group_test returns a null, right?

More questions on expressions...
- $(...|...|...), whats the use of the $ and | sign?
- for anything within "...", the value stored in that variable is compared?
- whats the difference if I use [ "$group_test" != "$group_name" ] instead?
- also difference between = and ==

Geez... i ask to much...

Thanks a lot~!

Thanks for the link 320mb~!

kenji1903 · 05-27-2004, 10:14 PM

Forgot another simple one; is there any difference between:
/usr/sbin/groupadd $group_name
and
/usr/sbin/groupadd "$group_name"

Thank you all~!

keefaz · 05-28-2004, 08:59 AM

There is no difference between /usr/sbin/groupadd $group_name and /usr/sbin/groupadd "$group_name". But when in test case the "" are needed to extrapolate the value from the variable.

For the question whats the use of the $ and | sign?, the $ sign means the result will be put in a variable and the | is a pipe symbol. It is a useful command line concept. It take the result of the previous command (before the | ) and work with it.
Example :
echo "Hello" | wc -c
echo "Hello" # print Hello
| wc -c # take Hello and display its number of char
You can use
[ "$group_test" != "$group_name" ]
or [ ! "$group_test" = "$group_name" ]
it is the same.

From the man bash :
"= may be used in place of == for strict POSIX compliance"
so you can use '=' or '==' for testing strings

I am not a bash expert but your prob interested me

also I doubt that the script will be usefull as the command groupadd will prevent you if a group already exist.

kenji1903 · 05-29-2004, 09:58 AM

Thanks a million, keefaz~!
That really cleared a lot of questions off my mind

I was actually trying to write a menu type of script to add groups, users and machine accounts

Why can't I create a directory after the group add command?

Code:

/usr/sbin/groupadd $group_name
mkdir /home/$group_name

i got an error that sounds like, cannot create directory

Something wrong with the syntax?

keefaz · 05-29-2004, 10:18 AM

do you run the script as root ? Maybe fix /home permissions
If home permissions are not
drwxr-xr-x 6 root root
do chmod 755 /home as root

kenji1903 · 05-29-2004, 08:39 PM

Mine's:
drwxr-xr-x 3 root root
By the way, i kind of forgot what the integer between the permission and ownership means, mind refreshing me on that?

I am root... thats why I was surprised why I can manually create a directory but not using a script...

keefaz · 05-29-2004, 11:32 PM

For the integer between permission and ownership in ls -l, do ls -a in a directory, count the directory files, then cd.. and do ls -l, you should see the same number in the second field of output ls -l ( between permission and ownership ).

I think your $group_name variable is not initialised (no value) so It can't create directory.

kenji1903 · 05-30-2004, 12:02 AM

Thanks bro

Umm... initialising it... I thought its initialised to the group name entered by the user?