Tar – How to Verify a Tar Archive

It shouldn't be very difficult, at least for archives that are compatible with the old-style format where file names are stored in a fixed-size (100 bytes) field, but I don't know of any tool that can rename a file in place in a tar archive. Besides, with a compressed archive, you'd need to create a new file anyway.

It should be even easier, but I don't know of any existing tool that can filter an archive, renaming files as it goes. You can build one on top of tar libraries in scripting languages; for example, here's a proof-of-concept script to rename a directory in a tar archive using Perl with Archive::Tar. The archive is loaded entirely into memory; this is an intrinsic limitation of Archive::Tar.

#!/usr/bin/env perl
## Usage: tar-rename OLDPREFIX NEWPREFIX
use strict;
use warnings;
use Archive::Tar;
my ($from, $to) = @ARGV;
my $tar = Archive::Tar->new(\*STDIN);
foreach my $file ($tar->get_files()) {
    my $name = $file->name;
    $name =~ s~\A\Q$from\E($|/)~$to$1~;
    $file->rename($name) unless $name eq $file->name;
}
$tar->write(\*STDOUT);

GNU tar doesn't have the ability to rename members on the fly, but pax (POSIX's replacement for cpio and tar) does. However, you can't make pax both read and write from an archive. What you can do is expose the archive as a regular tree through AVFS, and create a new archive with pax. This retains file names (except as transformed), contents, times and modes but resets file ownership to you (unless executed as root).

mountavfs
cd "~/.avfs$PWD/old.tgz#"
pax -w -s '!bar!baz!' -s '!bar/!baz/' . | gzip >new.tgz

The easy way, if you don't particularly need to use -C to tell tar to change to some other directory, is to simply specify the full path to the archive on the command line. Then you can be in whatever directory you prefer to create the directory structure that you want inside the archive.

The following will create the archive /var/www/file.tar.gz and put file1 from the current directory (whatever that happens to be) in it, with no in-archive path information.

tar czf /var/www/file.tar.gz file1

The path (to either the archive, the constituent files, or both) can of course also be relative. If file1 is in /tmp, you are in /var/spool and want to create the archive in /var/www, you could use something like:

tar czf ../www/file1.tar.gz /tmp/file1

There's a million variations on the theme, but this should get you started. Add the v flag if you want to see what tar actually does.