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.
The options are
- -if f
- Open file
f
for input.
- -of f
- Open file
f
for output.
- -ibs n
- Set input block size to
n
bytes (default 512).
- -obs n
- Set output block size (default 512).
- -bs n
- Set both input and output block size,
superseding
ibs
and
obs.
If no conversion is specified,
preserve the input block size instead of packing short blocks
into the output buffer.
This is particularly efficient since no in-core copy need be done.
- -cbs n
- Set conversion buffer size.
- -skip n
- Skip
n
input records before copying.
- -iseek n
- Seek
n
records forward on input file
before copying.
- -files n
- Catenate
n
input files (useful only for magnetic tape or similar input device).
- -oseek n
- Seek
n
records from beginning of output file before copying.
- -count n
- Copy only
n
input records.
- -conv ascii Convert
EBCDIC
to
ASCII.
- ebcdic
- Convert
ASCII
to
EBCDIC.
- ibm
- Like
ebcdic
but with a slightly different character map.
- block
- Convert variable length
ASCII
records to fixed length.
- unblock
- Convert fixed length
ASCII
records to variable length.
- lcase
- Map alphabetics to lower case.
- ucase
- Map alphabetics to upper case.
- swab
- Swap every pair of bytes.
- noerror
- Do not stop processing on an error.
- sync
- Pad every input record to
ibs
bytes.
Where sizes are specified,
a number of bytes is expected.
A number may end with
k
or
b
to specify multiplication by
1024 or 512 respectively;
a pair of numbers may be separated by
x
to indicate a product.
Multiple conversions may be specified in the style:
-conv ebcdic,ucase.
Cbs
is used only if
ascii,
unblock,
ebcdic,
ibm,
or
block
conversion is specified.
In the first two cases,
n
characters are copied into the conversion buffer, any specified
character mapping is done,
trailing blanks are trimmed and new-line is added
before sending the line to the output.
In the latter three cases, characters are read into the
conversion buffer and blanks are added to make up an
output record of size
n.
If
cbs
is unspecified or zero, the
ascii,
ebcdic,
and
ibm
options convert the character set without changing the block
structure of the input file; the
unblock
and
block
options become a simple file copy.