Manual page for DD(1)
dd - convert and copy files with various data formats
copies a specified input file to a 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
Input file is taken from
standard input is default.
Output file is taken from
standard output is default. Note:
creates an explicit output file; therefore the
option is usually useless with explicit
output except in special cases such as
using magnetic tape or raw disk files.
Input block size
bytes (default 512).
Output block size
bytes (default 512).
Set both input and output block size, superseding
also, if no conversion is specified,
it is particularly efficient since
no copy need be done. Block sizes for the Sun386i are 9k for 3.5-inch
floppy disks, and 126b (blocks) for quarter-inch tapes.
Conversion buffer size.
input records before starting copy
input files before terminating (makes sense only
when input is a magtape or similar device).
records from beginning of output file before copying. This option
generally only works with magnetic tapes and raw disk files and is
otherwise usually useless if the explicit output file
was named with the
Slightly different map of
Convert variable length records to fixed length.
Convert fixed length records to variable length.
Map alphabetics to lower case.
Map alphabetics to upper case.
Swap every pair of bytes.
Do not stop processing on an error.
Pad every input record to
- arg, arg[,...]
Several comma-separated conversions, for a combination of
effects. For instance,
is useful for reading variable-length output from a pipe.
Where sizes are specified, a number of bytes is expected.
A number may end with
(kilobytes) to specify multiplication by 1024,
(blocks of 512 bytes) to specify multiplication by 512,
(words) to specify multiplication by 4;
a pair of numbers may be separated by
to indicate a product.
is used only if
conversion is specified. In the first two cases,
characters are placed into the conversion buffer, any specified
character mapping is done, trailing blanks trimmed and
added before sending the line to the output.
In the latter three cases, characters are read into the
conversion buffer, and blanks added to make up an
output record of size
reports the number of whole and partial input and output blocks.
To read an
tape blocked ten 80-byte
card images per record into the
example% dd if=/dev/rmt0 of=x ibs=800 cbs=80 conv=ascii,lcase
Note: the use of raw magtape:
is especially suited to
on the raw physical devices because it
allows reading and writing in arbitrary record sizes.
The following write the file
to a 3.5-inch floppy and read from the floppy into a file
example% dd if=filename of=/dev/rfd0c bs=9k
example% dd if=/dev/rfd0c of=filename bs=9k
Sun386i files names are shown in
- f+p records in(out):
Numbers of full and partial records read(written).
conversion tables are taken from the 256 character standard in the
Nov, 1968. The
conversion, while less blessed as a standard,
corresponds better to certain
print train conventions. There is no universal solution.
options cannot be combined with the
silently ignore all but the last mutually-exclusive keyword.
Created by unroff & hp-tools.
© by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 21/April/97