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Full Discussion: validate tar file on tape
Top Forums Shell Programming and Scripting validate tar file on tape Post 302543682 by dernsdorff on Monday 1st of August 2011 05:19:57 PM
Old 08-01-2011
validate tar file on tape
I've got a KSH/AIX question that I haven't been able to figure out yet.

I've got a tape archive program that "tar's" data to a tape. After creating the archive, I'd like to somehow verify that the tape is actually good. So, what I'd like to do as a simple "sanity" check that I can read the tape is to view the first entry of the tar file listing, basically
Code:
tar -vtf/dev/rmt0 | head -1

If I can successfully read the first entry, I'll assume (hope) the whole archive is okay. If I get an error, then maybe the tape was bad or some other problem.

If I simply "tar -vtf/dev/rmt0", I'll immediatley see the first entry, as "stdout" is line buffered. However, when I pipe it to "head", stdout is fully buffered, so I don't see any output until the "tar" finishes processing the whole file.

I'd like to tar the file until I get the first entry (or an error) and then terminate the tar command.

I've tried numerous combinations of redirection, piping, background processes, coprocesses, etc, but I can't come up anything that works for me. I can redirect stdout to stderr (which isn't buffered) so that I can see the output immediately, but then I can't read the output to be able to terminate the tar command after the first entry is read.

Any ideas?

Thanks!

Don
Last edited by Franklin52; 08-02-2011 at 03:33 PM.. Reason: Please use code tags for data and code samples, thank you
 

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LEARN ABOUT DEBIAN

dds-dd

dds-dd(1)						      General Commands Manual							 dds-dd(1)

NAME

       dds-dd - tool to read a dds device.

SYNOPSIS

       dds-dd [ -f device ]

DESCRIPTION

       dds-dd  reads  a  dds  tape devices (DAT). Every block is read and written to stdout. A tape with unknown block size or blocks of different
       size can be read.

       The default device is /dev/rmt0, which may be overridden with the environment variable TAPE, which in  turn  may  be  overridden  with  the
       -f device option. The device must be a character special file.

OPTIONS

       -f device
	      Device of the tape archive (default is /dev/rmt0).  Must be a character special file connected to a dds tape device.

       -V,--version
	      Print the version number of mt-dds to stderr and exit immediately.

       --help print some screens of online help with examples through a pager and exit immediately.

EXAMPLES

       Example: Read the tape and make a listing:
		 dds-dd | tar ft -

       Example: Read the tape and make a listing:
		 dds-dd | cpio -it

ENVIRONMENT

       The environment variable TAPE overrides the default tape device /dev/rmt0.

       SEE ALSO
	      dds2tar(1), dds2index(1), mt(1), tar(1)

HISTORY

       This program was created to use it in conjunction with dds2tar.

AUTHOR

       J"org Weule (weule@cs.uni-duesseldorf.de), Phone +49 211 751409.  This software is available at ftp.uni-duesseldorf.de:/pub/unix/apollo

									2.4								 dds-dd(1)
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