#!/bin/sh

# truncate for linux

# Author: P@draigBrady.com

# V1.0      16 Dec 2005     Initial release

# This is a thin (but useful) wrapper around the
# IMHO confusing truncate functionality of dd.

# Note the FreeBSD util allows one to specify relative sizes,
# and to raise an error if the file doesn't exist.

if [ "$#" != "2" ]; then
    (
    echo "
Usage: `basename $0` <size> <path>

Truncate the <path> to exactly <size> bytes.

If <path> doesn't exist it is created.

<size> is a number which may be optionally followed
by the following multiplicative suffixes:
  b              512
  KB            1000
  K             1024
  MB       1000*1000
  M        1024*1024
and so on for G, T, P, E, Z, Y

If the file previously was larger than this size, the extra data is
lost. If the file previously was shorter, it is extended
and the extended part reads as zero bytes. Note in both cases
no data is written (if the filesystem supports holes in files).

E.G.: truncate 2TB ext3.test
"
    ) >&2
    exit 1
fi

size=$1
file="$2"

error=`dd bs=1 seek=$size if=/dev/null of="$file" 2>&1`
ret=$?
echo "$error" | grep -v "^0" >&2
exit $ret