VBLADE/vblade-master/sparsefile

   1 #! /bin/sh
   2 # sparsefile - create sparse files conveniently
   3 #
   4 # depends on dd and dc commands.
   5
   6 usage() {
   7         echo "usage: `basename $0` {10M|10G|10T} {filename}" 1>&2
   8 }
   9 size=$1
  10 if test "$size" = "-h"; then
  11         usage
  12         exit
  13 fi
  14 fnam=$2
  15
  16 die() {
  17         usage
  18         exit 1
  19 }
  20 set -e
  21 units=`echo "$size" | sed 's!.*\(.\)$!\1!'`
  22 n=`echo "$size" | sed 's!\(.*\).$!\1!'`
  23 test "$units" && test "$n" && test "$units" != "$n" || die
  24 case "$units" in
  25 M)
  26         seek=`echo "$n 1024 * 1 - p" | dc` ;;
  27 G)
  28         seek=`echo "$n 1024 1024 * * 1 - p" | dc` ;;
  29 T)
  30         seek=`echo "$n 1024 1024 1024 * * * 1 - p" | dc` ;;
  31 *)
  32         die
  33         ;;
  34 esac
  35 sh -xc "dd bs=1k count=1 if=/dev/zero of=$fnam seek=$seek"
  36 ls -lh "$fnam"