hpux 10.20 - dd (1)
NAME
dd - convert, reblock, translate, and copy a (tape) file
SYNOPSIS
dd [option=value] ...
DESCRIPTION
dd copies the specified input file to the specified output with
possible conversions. The standard input and output are used by
default. Input and output block size can be specified to take
advantage of raw physical I/O.
Options
dd recognizes the following option=value pairs:
if=file Input file name; default is standard input.
of=file Output file name; default is standard output. The
output file will be created using the same owner
and group used by creat().
ibs=n Input block size is n bytes (default 512).
obs=n Output block size is n bytes (default 512).
bs=n Set both input and output block size to the same
size, superseding ibs and obs. This option is
particularly efficient if no conversion is
specified, because no in-core copy is necessary.
cbs=n Conversion buffer size is n bytes.
skip=n Skip n input blocks before starting copy.
seek=n Seek n blocks from beginning of output file before
copying. This option is ignored on a raw magnetic
tape device. See mt(1) for information about
operations on raw magnetic tape devices.
count=n Copy only n input blocks.
conv=option Data conversion option. Use one of the following:
conv=ascii Convert EBCDIC to ASCII.
conv=ebcdic Convert ASCII to EBCDIC
conv=ibm Convert ASCII to EBCDIC
using an alternate
conversion table
conv=lcase Map US ASCII alphabetics to
lowercase
conv=ucase Map US ASCII alphabetics to
uppercase
conv=swab Swap every pair of bytes
conv=noerror Do not stop processing on
an error
conv=sync Pad every input block to
input block size (ibs)
conv=notrunc Do not truncate existing
file on output
conv=block Convert input record to a
fixed length specified by
cbs
conv=unblock Convert fixed length
records to variable length
conv=..., ... Multiple comma-separated
conversions
Where sizes are required, n indicates a numerical value in bytes.
Numbers can be specified using the forms:
n for n bytes
nk for n Kbytes (n x 1024),
nb for n blocks (n x 512), or
nw for n words (n x 2).
To indicate a product, use x to separate number pairs.
The cbs option is used when block , unblock , ascii or ebcdic
conversion is specified. In case of ascii , cbs characters are placed
into the conversion buffer, converted to ASCII, trailing blanks are
trimmed, and a new-line is added before sending the line to the
output. In case of ebcdic , ASCII characters are read into the
conversion buffer, converted to EBCDIC, and blanks are added to make
up an output block of size cbs.
Upon completion, dd reports the number of whole and partial input and
output records.
EXTERNAL INFLUENCES
International Code Set Support
Single- and multibyte character code sets are supported.
Environment Variables
The following environment variables will affect execution of dd :
LANG determines the locale when LC_ALL and a corresponding variable
(beginning with LC_) do not specify a locale.
LC_ALL determines the locale used to override any values set by LANG
or any environment variables beginning with LC_.
The LC_CTYPE variable determines the locale for the interpretation of
sequences of bytes of text data as characters ( single/multiple byte
characters, upper/lower case characters ).
The LC_MESSAGES variable determines the language in which messages
should be written.
RETURN VALUE
Exit values are:
0 Successful completion.
>0 Error condition occurred.
DIAGNOSTICS
f+p records in Number of full and partial blocks read.
f+p records out Number of full and partial blocks written.
EXAMPLES
Read an EBCDIC tape blocked ten 80-byte EBCDIC card images per block
into an ASCII file named x:
dd if=/dev/rmt/c0t0d0BEST of=x ibs=800 cbs=80
conv=ascii,lcase
Note the use of the raw magnetic tape device file. dd is especially
suited to I/O on raw physical devices because it allows reading and
writing in arbitrary block sizes.
WARNINGS
You may experience trouble writing directly to or reading directly
from a cartridge tape. For best results, use tcio(1) as an input or
output filter. For example, use
... |dd ... |tcio -ovVS 256 /dev/rct/c4t1d0
for output to a cartridge tape, or
tcio -ivS 256 /dev/rct/c4t1d0 |dd ... | ...
for input from a cartridge tape.
Some devices, such as 1/2-inch magnetic tapes, are incapable of
seeking. Such devices must be positioned prior to running dd by using
mt(1) or some other appropriate command.
ASCII and EBCDIC conversion tables are taken from the 256-character
ACM standard, Nov, 1968. The ibm conversion, while less widely
accepted as a standard, corresponds better to certain IBM print train
conventions. There is no universal solution.
New-line characters are inserted only on conversion to ASCII; padding
is done only on conversion to EBCDIC. These should be separate
options.
If if or of refers to a raw disk, bs should always be a multiple of
sector size of disk. The default bs size used by dd is 512 bytes. If
sector size of disk is different from 512 bytes, a bs multiple of
sector size should be specified. The character special (raw) device
file should always be used for devices.
It is entirely up to the user to insure there is enough room in the
destination file, filesystem and/or device to contain the output since
dd(1) cannot pre-determine the required space after conversion.
SEE ALSO
cp(1), mt(1), tr(1), disk(7), mt(7).
STANDARDS CONFORMANCE
dd: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2