Shell Programming and Scripting

Another tip from the 1980's ... adjust your file selection list fed to the tar command to include some "First" and "Last" file. You can then write a script to verify the integrity of your tapes (before sending off-site?) by reading back the "First" and "Last" files. If you accidentally overflowed your tape, or the tape is "bad", you'll be missing the "Last" file when your tar -x completes, prompting further investigation.

I think the requirement was to avoid a second full pass on tape.

I figured head would stop tar and the tape when it wrote to EOF or got EPIPE: Not beautiful, but simple.

Sorry, I assumed the original poster wanted, in his own words, to verify that the tape is actually good. IMHO, Reading the first few blocks for the tar header and perhaps a portion of the first file is not sufficient. If the purpose of writing the tape is to have the assurance of a restorable backup, the time spent performing a full read pass over the tape is a small price to pay for the peace of mind that actually knowing a backup is valid provides.

That being said, the quick and dirty kludge would be to use:

Code:

$ dd if=/dev/rmt0 bs=20b count=1 2>/dev/null | tar -tvf - 2>/dev/null | head -1

..to get the first filename off of his tape.