README for truncate
===================
Jason Stephenson <[email protected]>
v1.0, 12 September 2017

DESCRIPTION
-----------

The truncate utility adjusts the length of each regular file given on
the command-line.

This is the FreeBSD implementation of truncate with modifications for
OpenBSD.  The FreeBSD VCS tags have been removed, along with the
includes for the libutil library headers.  (The latter does not exist
on OpenBSD.)  The expand_number function was copied from the libutil
sources and modified in a similar manner to the code for the truncate
utility.

INSTALLATION
------------

This repository uses GNU Autoconf to build.  You will need to install
autoconf-2.69 and automake-1.9.  To build and install to /usr/local/
on OpenBSD, run the following commands in your local repository:

    AUTOCONF_VERSION=2.69 AUTOMAKE_VERSION=1.9 autoreconf -i
    ./configure
    make
    doas make install

You can install to other locations by using the --prefix option to
configure.  For instance, to install into the current user's home
directory the following steps will work:

    AUTOCONF_VERSION=2.69 AUTOMAKE_VERSION=1.9 autoreconf -i
    ./configure --prefix=$HOME
    make
    make install

NOTE: Later versions of autoconf and automake should work.  Adjust the
version variables as appropriate.

Two files are currently installed by the above commands:

* the truncate binary in $PREFIX/bin
* the truncate.1 man page in $PREFIX/share/man/man1

These can be manually deleted in order to remove truncate.

SYNOPSIS
--------

    truncate [-c] -s [+|-]size[K|k|M|m|G|g|T|t] file ...
    truncate [-c] -r rfile file ...


The following options are available:

    -c      Do not create files if they do not exist.  The truncate utility
            does not treat this as an error.  No error messages are displayed
            and the exit value is not affected.

    -r rfile
            Truncate or extend files to the length of the file rfile.

    -s [+|-]size[K|k|M|m|G|g|T|t]
            If the size argument is preceded by a plus sign (+), files will
            be extended by this number of bytes.  If the size argument is
            preceded by a dash (-), file lengths will be reduced by no more
            than this number of bytes, to a minimum length of zero bytes.
            Otherwise, the size argument specifies an absolute length to
            which all files should be extended or reduced as appropriate.

            The size argument may be suffixed with one of K, M, G or T
            (either upper or lower case) to indicate a multiple of Kilobytes,
            Megabytes, Gigabytes or Terabytes respectively.

Exactly one of the -r and -s options must be specified.

If a file is made smaller, its extra data is lost.  If a file is made
larger, it will be extended as if by writing bytes with the value
zero.  If the file does not exist, it is created unless the -c option
is specified.

Note that, while truncating a file causes space on disk to be freed,
extending a file does not cause space to be allocated.  To extend a
file and actually allocate the space, it is necessary to explicitly
write data to it, using (for example) the shell's '>>' redirection
syntax, or dd(1).

EXIT STATUS
-----------

The truncate utility exits 0 on success, and >0 if an error occurs.
If the operation fails for an argument, truncate will issue a
diagnostic and continue processing the remaining arguments.

STANDARDS
---------

The truncate utility conforms to no known standards.

HISTORY
-------

The truncate utility first appeared in FreeBSD 4.2.

AUTHORS
-------

The truncate utility was written by Sheldon Hearn
<[email protected]>.

The truncate utility includes code that is copyright 2007 by Eric
Anderson <[email protected]> and Pawel Jakub Dawidek
<[email protected]>.

The truncate utility was ported to OpenBSD 6.1 by Jason Stephenson
<[email protected]>.

LICENSE
-------

The truncate utility C source code files are covered by the 2-clause,
FreeBSD license.  See the file COPYING for the actual license.

The Makefile.am files are covered by the OpenBSD license.  See the
files themselves for the details.