[Help-tar] Global header contents as environment varia bles of the external program called with --to-command option

[Дмитрий Иванов]

Hello,

I plan to use the GNU tar software with POSIX format to save data with some metadata in tape archives. The metadata will be saved as couple of keyword-value pairs in the tar's global header (with --pax-option). During the reading of a tar archive from the tape I'd like to do some "on the fly" metadata processing with tar option --to-command <external_program>. 
It would be nice to have saved keyword-values as a variables in the environment of that <external_program> (like other stuff: TAR_MTIME, TAR_ATIME,...).
Is it real? 

Thanks,
Dmitry Ivankov