Shell Programming and Scripting

Hi I am trying to learn shell script and i ran into an issue.

I am trying to read a file with few directories and tar them up.
I used a while loop but i end up overwriting tar file with only the last directory in the file being tared .

Code:

cat test.txt |
(
while read line
do
tar -czPf backup.tar.gz $line
done
)

If test.txt has test1, backup1, goo1

I end up having only goo1 in the tar

how do i get all 3 directories in the tar?

Thanks for your help in advance

That is useless use of cat..

Please see man pages for tar

tar -c is used to create new archieve.. try using tar -r
try

Code:

while read line
do
tar -rzPf backup.tar.gz $line
done<test.txt

Every time the loop runs, it creates the tar file in the same name (backup.tar.gz) thus over writing the previous one, hence it ends up only with the last tared file.
The tar command in your while loop should have variable for both source and destination.

Try this:

Code:

cat test.txt |
(
while read line
do
tar -czPf  backup_$line.tar.gz  $line
done
)

Hi Pamu,

I used -r but my understanding is it can used only if tar file already exists .. i am creating a new tar so it did not work

you can just create a empty tar file, then use that tar file in while loop

Code:

 
tar czPf backup.tar.gz --files-from /dev/null

You can create empty tar file as per itkamaraj's suggestion.

or add this to the command for checking presence of tar file

Code:

if [[ -f backup.tar.gz ]]
then
tar -rzPf backup.tar.gz file
else
tar -czPf backup.tar.gz file
fi