BaSH: another problem with script

[imported_Frank]

Yep yep, it's me again!

In my kick-ass script *roll eyes*, I want to do a tarball backup of a user's home directory and then delete the user's account and the user's home directory, leaving a tarball backup of the deleted directory in /root/users_deleted.

Here's the part of the script:

echo -n "Removing $2..."
if cat /etc/passwd | grep "^$2:" > /dev/null; then
tar -czf /root/users_deleted/$2_'date +"%Hh%M_%d-%m-%Y"'.tgz /home/$2
if [ $? == 0 ]; then
$userdel $2
if cat /etc/passwd | grep "^$2:" > /dev/null; then
echo " Done."
exit 0
else
echo " ERROR: Could not delete account."
exit 1
fi
else
echo " ERROR: Could not create a backup of $2's files."
exit 1
fi
else
echo " ERROR: $2 does not exist."
exit 1
fi

With this version of the script, it does create the backup file (even though the date doesn't show correctly, it prints date +"%Hh%M_%d-%m-%Y" as the filename (after $2_ of course).

The problem with the script is that it always give me the error that it couldn't create a backup of the user's file. I guess it isn't working mainly because of the bad filename of the tarball..?


Thanks, Frank

 

[sciencewhiz]

Are you using ` or ' for the date command? (the first is under the tilde, the second is the single quote)

 

[imported_Frank]

Single quote, even though, could there be anything else causing the script error?

Thanks, Frank

 

[imported_Frank]

Ooops, was wrong, I used `, not single quotes.

If I remember, I tried modifying the script to try it with `s, 's and "s.

Which one should I use for date, so I could work on the problem while being sure that I used the right quotation..?


Thanks, Frank

 

[imported_Frank]

I worked some time on it and now it works better, it says, as the error:

Removing blablabla...tar: Removing leading `/' from member names
./setup_user: line 56: blablabla: command not found
Done.

Looks like it performs $2 as a command?!?!?!?

BTW: As soon as this part works, I'll > /dev/null the output of tar to hide the Removing leading`/` from member names.. it's quite ugly


Thanks, Frank

 

[n0cmonkey]

#!/bin/bash

tar -cvf /tmp/$1.tar /home/$1
gzip /tmp/$1.tar
mv /tmp/$1.tar.gz /root/users_deleted/$1.`date +%d%m%Y`.tar.gz
rmuser $1



$2 would be the third thing you type in:
rm stuff.txt menu.pdf
menu.pdf is $2, stuff.txt is $1, rm is $0.

 

[Barnaby W. Füi]

Backticks (`) run the contained text as a command, and return the text. So this:

echo "hi"

is the same as:

echo `echo "hi"`

 

[drag]

To remember the differences between the qoutes just keep this script around and run it time to time. I do stuff like this to remind myself of different -isms of stuff incase I forget it.

#! /bin/bash

TEST="ls /"

echo "This is the test"
echo " "
echo " "
echo "This is what happens when you use double qoutes. \" \""
echo "$TEST"
echo " "
echo "This is what happens when you use single qoutes. \' \'"
echo '$TEST'
echo " "
echo "This is what happens when you use backticks. \` \`"
echo `$TEST`
echo " "
echo " "
echo "See also what this looks like:"
echo "double qoutes"
echo "hello \" \""
echo " "
echo "single qoutes"
echo 'hello \" \"'
echo " "
echo "but look at the back tick. we get a error:"
echo `hello \" \"`
echo " "
echo " "
echo "Variations"
echo "This is a third type. By using ( ) you can create a new bash enviroment temperarially for whatever reason"
pwd
echo " "
(cd /etc; pwd; cd /var/; pwd; cd /usr/bin/ ; pwd)
echo "but we never went anywere:"
pwd
echo " "

 

[Cheetah8799]

Advanced Bash-Scripting Guide

hope this helps.

 

[imported_Frank]

Ah!

Thanks all for the answers, I got everything working properly now. The only problem is the /dev/null'ing of some commands that doesn't work.. :S

Is there any way of "muting" a command by using quotes? > /dev/null isn't working on every command that outputs something.


Thanks, Frank

 

[aspitzer]

"> /dev/null" only sends stdout to /dev/null, anytime you have errors, or something that writes to stderr, it will still appear on the screen, as in:

rm -f /etc > /dev/null
rm: cannot remove `/etc': Permission denied

vs

rm -f /etc > /dev/null 2>&1

the 2>&1 says to also send the stderr to stdout, which then goes to /dev/null

 

[imported_Frank]

Originally posted by: aspitzer
rm -f /etc > /dev/null 2>&1

Ahh, you are right, I forgot this one :S

Is 2> /dev/null the same as > /dev/null 2>&1?


Thanks, Frank

 

[aspitzer]

[aspitzer@oscar aspitzer]$ rm -f /etc 2>/dev/null
[aspitzer@oscar aspitzer]$ rm -f /etc > /dev/null 2>&1
[aspitzer@oscar aspitzer]$ rm -f /etc > /dev/null
rm: cannot remove `/etc': Permission denied

looks like it!

 

[imported_Frank]

I did a few tests and it pointed me out that 2> /dev/null is not the same as > /dev/null 2>&1. From my tests, I think that the difference is that the first one only hides the error messages and the second one hides the error messages AND the normal stdout messages.


Frank

 

[Barnaby W. Füi]

Is 2> /dev/null

.. sends stderr to /dev/null, which means that you won't see any error messages, but you'll see normal output (stdout).

ls > /dev/null 2>&1

.. sends stdout to /dev/null, which means you won't see normal output. 2>&1 sends stderr to stdout, and since stdout is being redirected to /dev/null, that means that stderr will go there as well. You won't see any output.

(oh, 1 is stdout, 2 is stderr. stdout is "standard output," for normal text output. stderr is "standard error," which is for errors. 0 is stdin, and that's used for input instead of output. When you type text into a prompt, that text is generally sent to stdin. These are the three "standard" file descriptors.)