Unable to untar a file?

Question

I have written a shellscript which tries to pull a tar file from an ftp server and untar it locally. I need to extract specific files from the tar archive. The filename of the tarfile contains a date; I need to be able to select a tar file based on this date.

abc_myfile_$date.tar is the format of the file I am pulling from the ftp server.

My current code looks like this:

for host in ftpserver
do
ftp -inv host <<END_SCRIPT
user username password
prompt
cd remotepath
lcd localpath
mget *myfile_$date*.tar
quit
END_SCRIPT
done

for next in `ls localpath/*.tar`
do
tar xvf $next *required_file_in_tar_file*.dat
done

when i run the script am not able to untar the files

I am able to get a single tar file from the ftp server only if I mention the exact name of that file. I would like to get a file which has myfile_$date in its name. After this I would like to extract it to a local path to get the specified files in that tar file whose names consist of my required_files.

Answer 1

I'm not quite sure, but does the FTP protocol not have a command mget if you want to download multiple files? (instead of get)

Answer 2

You get the .tar file, but decompress it with z option. Compressed files (those that require z) normally have .tar.gz prefix. Try

tar xvf $next *required_file_in_tar_file*.dat

Answer 3

Firstly, if you want to use wildcards for the file name that you're getting from the server you need to use mget instead of get. Wildcard file expansion (the *) does not work for the get command.
Once you have pulled the file the tar operation will work as expected, most modern versions of linux/bsd have a 'smart' tar, which doesn't need the 'z' command to specify that the tar file is compressed - they'll figure out that the tarball is compressed on their own and uncompress it automatically, providing the appropriate compression/decompression tool is on the system (bzip2 for .jz files, gzip for .gz files).