linux man page for truncate

TRUNCATE(1)							   User Commands						       TRUNCATE(1)

NAME
       truncate - shrink or extend the size of a file to the specified size

SYNOPSIS
       truncate OPTION... FILE...

DESCRIPTION
       Shrink or extend the size of each FILE to the specified size

       A FILE argument that does not exist is created.

       If  a  FILE  is	larger than the specified size, the extra data is lost.  If a FILE is shorter, it is extended and the extended part (hole)
       reads as zero bytes.

       Mandatory arguments to long options are mandatory for short options too.

       -c, --no-create
	      do not create any files

       -o, --io-blocks
	      treat SIZE as number of IO blocks instead of bytes

       -r, --reference=FILE
	      use this FILE's size

       -s, --size=SIZE
	      use this SIZE

       --help display this help and exit

       --version
	      output version information and exit

       SIZE may be (or may be an integer optionally followed by) one of following: KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T,
       P, E, Z, Y.

       SIZE  may also be prefixed by one of the following modifying characters: `+' extend by, `-' reduce by, `<' at most, `>' at least, `/' round
       down to multiple of, `%' round up to multiple of.

       Note that the -r and -s options are mutually exclusive.

AUTHOR
       Written by Padraig Brady.

REPORTING BUGS
       Report truncate bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>
       Report truncate translation bugs to <http://translationproject.org/team/>

COPYRIGHT
       Copyright (C) 2010 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO
       dd(1), truncate(2), ftruncate(2)

       The full documentation for truncate is maintained as a Texinfo manual.  If the info and truncate programs are properly  installed  at  your
       site, the command

	      info coreutils 'truncate invocation'

       should give you access to the complete manual.

GNU coreutils 8.5						   February 2011						       TRUNCATE(1)