DD(1) — HP-UX
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. The input and output block size may be specified to take advantage of raw physical I/O.
option values
if=file input file name; standard input is default
of=file output file name; standard output is default
ibs=n input block size n bytes (default 512)
obs=n output block size (default 512)
bs=n set both input and output block size, superseding ibs and obs; also, if no conversion is specified, it is particularly efficient since no in-core copy need be done
cbs=n conversion buffer size
skip=n skip n input blocks before starting copy
seek=n seek n blocks from beginning of output file before copying
count=n copy only n input blocks
conv=ascii convert EBCDIC to ASCII
conv=ebcdic convert ASCII to EBCDIC
conv=ibm slightly different map of ASCII to EBCDIC
conv=lcase map alphabetics to lowercase
conv=ucase map 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
conv=... , ... several comma-separated conversions
Where sizes are specified, a number of bytes is expected. A number may end with k, b, or w to specify multiplication by 1024, 512, or 2, respectively; a pair of numbers may be separated by x to indicate a product.
The cbs option is used only if ascii or ebcdic conversion is specified. In the former case cbs characters are placed into the conversion buffer, converted to ASCII, and trailing blanks are trimmed and a new-line is added before sending the line to the output. In the latter case ASCII characters are read into the conversion buffer, converted to EBCDIC, and blanks added to make up an output block of size cbs.
After completion, dd reports the number of whole and partial input and output blocks.
DIAGNOSTICS
f+p blocks in(out)numbers of full and partial blocks read(written)
EXAMPLES
This command will read an EBCDIC tape blocked ten 80-byte EBCDIC card images per block into the ASCII file x:
dd if=/dev/rmt/0m of=x ibs=800 cbs=80 conv=ascii,lcase
Note the use of raw magtape. Dd is especially suited to I/O on the 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/c0
for output to a cartridge tape, and
tcio −ivS 256 /dev/rct/c0 | 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.
The ASCII/EBCDIC conversion tables are taken from the 256-character standard in the CACM 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-lines are inserted only on conversion to ASCII; padding is done only on conversion to EBCDIC. These should be separate options.
SEE ALSO
INTERNATIONAL SUPPORT
8- and 16-bit data, 8-bit file names.
Hewlett-Packard Company — May 11, 2021