bash assistance requested..

Ateo · 02-09-2005, 06:13 PM

Hi. I'm trying to write my own script that will back up user directories. I wanted this script to backup all user directories based on the user group. So far, I have a simple script that'll backup whatever directory/directories I want. What I can't seem to get right is extracting the line containing users from /etc/group, ie:

Code:

root@epitaph portage # cat /etc/group | grep users
users:x:100:user1,user2,user3

I know what I need, I just don't how to parse it. I need the users (user1,user2,user3) to be extracted and commas replaced with spaces so that I can use that output as a space delimited variable for a bash for loop, ie:

Code:

userlist="user1 user2 user3"
for user in $userlist

Thanks

Tinkster · 02-09-2005, 06:31 PM

Quote:

Originally posted by Ateo

Code:

root@epitaph portage # cat /etc/group | grep users
users:x:100:user1,user2,user3

Code:

userlist="user1 user2 user3"
for user in $userlist

Try

Code:

root@epitaph portage # userlist=`grep users /etc/group  |cut -d":" -f 4|tr "," " "`

Cheers,
Tink

druuna · 02-09-2005, 06:41 PM

Hi,

There are many ways of doing this, here are 2.

A mix of awk and sed. Probably one of the simpler ones:

grep audio /etc/group | awk -F: '{ print $NF }' | sed 's/,/ /'

In the above example awk sets its field seperator to a : and prints the last field, which are the users with the comma still present. The sed part takes care of the comma.

And one which uses only sed, should be faster:

grep users /etc/group | sed -e 's/.*:$.*$/\1/' -e 's/,/ /'

2 sed parts. The first part (between the 2 -e's ) seperates the users from the rest by using the greediness of a regular expression ( .*: is everything up to and including the last : ) The part between $ and $ is what is needed and can be printed with the \1
The second part replaces the comma with a space.

Up to you to fill a variable with it.

Hope this helps.

Ateo · 02-09-2005, 06:41 PM

Excellent. It worked, with modifications....

Code:

usergrp="100"
userlist=`grep $usergrp /etc/group | cut -d":" -f 4|tr "," " "`
echo $userlist

Thanks a bunch!

I ended up needing to use the user group number as using "users" would also grep smbusers...