tar/scripts/tarcat

#! /bin/sh
# Usage: tarcat volume1 volume2 ...
# concatenates a GNU tar multi-volume archive into a single tar archive.
# Author: Bruno Haible <bruno@clisp.org>, Sergey Poznyakoff <gray@gnu.org.ua>

# dump_type FILE [N]
# Print type character from block N (default 0) of tar archive FILE
dump_type() {
  dd if="$1" skip=${2:-0} bs=512 count=1 2>/dev/null |
    tr '\0' ' ' |
    cut -c157
}

case `dump_type "$1"` in
  [gx]) PAX=1;;
esac

cat "$1"
shift
for f
do
  SKIP=0
  T=`dump_type "$f"`
  if [ -n "$PAX" ]; then
    if [ "$T" = "g" ]; then
      # Global extended header.... 2 blocks
      # Extended header........... 2 blocks
      # Ustar header.............. 1 block
      # FIXME: This calculation is will fail for very long file names.
      SKIP=5
    fi
  else
    if [ "$T" = "V" ]; then
      T=`dump_type "$f" 1`
    fi
    if [ "$T" = "M" ]; then
      SKIP=$(($SKIP + 1))
    fi
  fi
  dd skip=$SKIP if="$f"
done