/usr.bin/truncate/truncate.1
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- .\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
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- .Dd December 19, 2006
- .Dt TRUNCATE 1
- .Os
- .Sh NAME
- .Nm truncate
- .Nd truncate or extend the length of files
- .Sh SYNOPSIS
- .Nm
- .Op Fl c
- .Bk -words
- .Fl s Xo
- .Sm off
- .Op Cm + | -
- .Ar size
- .Op Cm K | k | M | m | G | g | T | t
- .Sm on
- .Xc
- .Ek
- .Ar
- .Nm
- .Op Fl c
- .Bk -words
- .Fl r Ar rfile
- .Ek
- .Ar
- .Sh DESCRIPTION
- The
- .Nm
- utility adjusts the length of each regular file given on the command-line.
- .Pp
- The following options are available:
- .Bl -tag -width indent
- .It Fl c
- Do not create files if they do not exist.
- The
- .Nm
- utility does not treat this as an error.
- No error messages are displayed
- and the exit value is not affected.
- .It Fl r Ar rfile
- Truncate or extend files to the length of the file
- .Ar rfile .
- .It Fl s Xo
- .Sm off
- .Op Cm + | -
- .Ar size
- .Op Cm K | k | M | m | G | g | T | t
- .Sm on
- .Xc
- If the
- .Ar size
- argument is preceded by a plus sign
- .Pq Cm + ,
- files will be extended by this number of bytes.
- If the
- .Ar size
- argument is preceded by a dash
- .Pq Cm - ,
- file lengths will be reduced by no more than this number of bytes,
- to a minimum length of zero bytes.
- Otherwise, the
- .Ar size
- argument specifies an absolute length to which all files
- should be extended or reduced as appropriate.
- .Pp
- The
- .Ar size
- argument may be suffixed with one of
- .Cm K ,
- .Cm M ,
- .Cm G
- or
- .Cm T
- (either upper or lower case) to indicate a multiple of
- Kilobytes, Megabytes, Gigabytes or Terabytes
- respectively.
- .El
- .Pp
- Exactly one of the
- .Fl r
- and
- .Fl s
- options must be specified.
- .Pp
- 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
- .Fl c
- option is specified.
- .Pp
- 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
- .Ql >>
- redirection syntax, or
- .Xr dd 1 .
- .Sh EXIT STATUS
- .Ex -std
- If the operation fails for an argument,
- .Nm
- will issue a diagnostic
- and continue processing the remaining arguments.
- .Sh SEE ALSO
- .Xr dd 1 ,
- .Xr touch 1 ,
- .Xr truncate 2
- .Sh STANDARDS
- The
- .Nm
- utility conforms to no known standards.
- .Sh HISTORY
- The
- .Nm
- utility first appeared in
- .Fx 4.2 .
- .Sh AUTHORS
- The
- .Nm
- utility was written by
- .An Sheldon Hearn
- .Aq sheldonh@starjuice.net .