emulate-gnu-tar

#!/bin/sh

# emulate-gnu-tar -- emulate the options of GNU tar that librep uses
# in its tar-file handling code.

# $Id$

compression_mode=""
command=""
tarfile=""
to_stdout=""

version="1.0"

original_directory=`pwd`

usage () {
  cat <<EOF
usage: emulate-gnu-tar [OPTIONS..] COMMAND

Supported options include:

	--compress
	--gzip
	--bzip2
	--xz
	--lzma

Supported commands include:

	--version
	--list --file TARFILE --verbose
	--extract --file TARFILE -C DIR
	--extract --file TARFILE --to-stdout FILE

EOF
}

absolutify () {
  case "$1" in
    /*)
      echo $1
      ;;
    *)
      echo "$original_directory/$1"
      ;;
  esac
}

while [ x"$1" != x ]; do
  case $1 in
    --version)
      cat <<EOF
tar (GNU tar) $version
This isn't really GNU tar. It's just a wrapper script used by librep to
make proprietary tars look somewhat like GNU tar. Don't use it.
EOF
      exit 0
      ;;
    
    --compress)
      compression_mode=compress
      ;;

    --gzip)
      compression_mode=gzip
      ;;

    --bzip2)
      compression_mode=bzip2
      ;;

    --xz)
      compression_mode=xz
      ;;

    --lzma)
      compression_mode=lzma
      ;;

    --file)
      tarfile=`absolutify "$2"`
      shift
      ;;

    --verbose)
      ;;

    -C)
      cd "$2"
      shift
      ;;

    --to-stdout)
      to_stdout=$2
      shift
      ;;

    --extract)
      command=extract
      ;;

    --list)
      command=list
      ;;

    *)
      echo "unknown option: $1" >&2
      exit 1
      ;;
  esac
  shift
done

if [ "x$command" = x ]; then
  usage
  exit 1
fi

case "$compression_mode" in
  gzip)
    input="gzip -d -c \"$tarfile\" |"
    ;;

  compress)
    input="compress -d -c \"$tarfile\" |"
    ;;

  bzip2)
    input="bzip2 -d -c \"$tarfile\" |"
    ;;

  xz)
    input="xz -d -c \"$tarfile\" |"
    ;;

  lzma)
    input="lzma -d -c \"$tarfile\" |"
    ;;

  *)
    input="cat \"$tarfile\" |"
    ;;
esac

case "$command" in
  list)
    eval "$input tar tvf -"
    ;;

  extract)
    if [ "x$to_stdout" = "x" ]; then
      eval "$input tar xf -"
      exit $?
    else
      # Extract the file to a temporary directory, then cat it..
      tmpdir="/tmp/rep-emulate-gnu-tar.$$.output"
      mkdir "$tmpdir" || exit $?
      cd "$tmpdir"
      eval "$input tar xf - $to_stdout" || ( rm -rf $tmpdir && exit $? )
      cat "$to_stdout"
      cd "$original_directory"
      rm -rf "$tmpdir"
      exit 0
    fi
    ;;

  *)
    echo "Unimplemented command: $command"
    exit 1
    ;;
esac