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122 lines
3.8 KiB
Python
Executable file
122 lines
3.8 KiB
Python
Executable file
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""\
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==============================================
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mksparse.py - sparse file / disk image creator
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==============================================
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Usage: mksparse.py <imagefile.img> <size>[k|m|g]
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This will create <imagefile.img> with size <size>. If the suffix is
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not given then the size is in bytes, 'k' stands for kilobytes (1024),
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'm' for megabytes and 'g' for gigabyes (K/M/G are not implemented, one
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can type 000 easy enough).
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Simple python script that creates sparse files on unix / Win2k NTFS5.
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This script opens a file for writing, seeks at the desired position
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(or file size) and truncates the file there. Can be handy while
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playing with KVM / qemu / bochs / loopback images.
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Tested on linux-2.6+ only.
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NB: Check fallocate from util-linux, may work better for you.
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Author: Doncho N. Gunchev <gunchev at gmail dot com>
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Based on Brad Watson's work mkimage.py from
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http://lists.gnu.org/archive/html/qemu-devel/2004-07/msg00733.html
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http://qemu.dad-answers.com/download/qemu/utilities/QEMU-HD-Create/
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"""
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import os.path
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import re
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import sys
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__version__ = "0.3"
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__author__ = "Doncho Gunchev <gunchev@gmail.com>, Brad Watson"
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__depends__ = ['Python-3']
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#__copyright__ = """Have to ask Brad Watson, GPL?"""
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class MkSparseError(Exception):
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"""MkSpace errors"""
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def mk_sparse(file_name, file_size):
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"""Create a sparse file by truncating it at given position"""
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try:
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sparse_file = open(sys.argv[1],"wb+")
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except (IOError, OSError) as exc:
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raise MkSparseError("Error: Can't create file '" + file_name + "':\n"
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+ str(exc))
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else:
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try:
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# Note that I don't wan (you too) to write() anything in the file
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# because this will consume at least one sector/block.
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sparse_file.truncate(int(file_size))
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except (IOError, OSError) as exc:
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try:
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sparse_file.close() # clean the mess...
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os.unlink(sys.argv[1])
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except (IOError, OSError):
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pass
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raise MkSparseError("Error: Can't truncate '%s'\n%s"
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% (file_name, str(exc)))
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try:
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sparse_file.close()
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except (IOError, OSError) as exc:
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raise MkSparseError("Error: Can't close '%s'\n%s" % (file_name,
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str(exc)))
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def main():
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"""The main function for a command line execution"""
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if len(sys.argv) != 3:
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# .pyo (docstrings stripped) workaround
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print((__doc__ and __doc__
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or "Usage: mksparse.py <image-name> <size>[kmg]"), file=sys.stderr)
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print("Version:", __version__, file=sys.stderr)
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sys.exit(1)
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# 'Process' command line parameters
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file_name = sys.argv[1]
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file_size = sys.argv[2]
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# validate file size
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try:
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(size, dim) = re.match('^(\d+)([KkMmGg])?$', file_size).groups()
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except TypeError:
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print((sys.argv[0] + ': '
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+ "Bad image size given: " + repr(file_size)), file=sys.stderr)
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sys.exit(2)
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# Check if the file exists, -f (force) would be a good parameter
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if os.path.exists(file_name):
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print((sys.argv[0] + ': '
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+ ("Error: file (directory) '%s' already exists!" % (file_name))), file=sys.stderr)
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sys.exit(3)
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dim = dim.lower()
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# Calculate size in bytes
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size = int(size)
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if dim == 'k':
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size *= 1024
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elif dim == 'm':
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size *= 1024 * 1024
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elif dim == 'g':
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size *= 1024 * 1024 * 1024
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elif dim != None:
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print((sys.argv[0] + ': '
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+ "Internal error: size modifier " + repr(dim) + " not handled."), file=sys.stderr)
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sys.exit(4)
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file_size = size
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try:
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mk_sparse(file_name, file_size)
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except MkSparseError as exc:
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print(sys.argv[0] + ': ' + str(exc), file=sys.stderr)
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sys.exit(1)
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if __name__ == "__main__":
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main()
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