Manual page for DD(1)
dd - convert and copy files with various data formats
SYNOPSIS
dd
[
option=value
] ...
DESCRIPTION
dd
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
physical I/O.
OPTIONS
- if=name
-
Input file is taken from
name;
standard input is default.
- of=name
-
Output file is taken from
name;
standard output is default. Note:
dd
creates an explicit output file; therefore the
seek
option is usually useless with explicit
output except in special cases such as
using magnetic tape or raw disk files.
- ibs=n
-
Input block size
n
bytes (default 512).
- obs=n
-
Output block size
n
bytes (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 copy need be done. Block sizes for the Sun386i are 9k for 3.5-inch
floppy disks, and 126b (blocks) for quarter-inch tapes.
- cbs=n
-
Conversion buffer size.
- skip=n
-
Skip
n
input records before starting copy
- files=n
-
Copy
n
input files before terminating (makes sense only
when input is a magtape or similar device).
- seek=n
-
Seek
n
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
of
option.
- count=n
-
Copy only
n
input records.
- conv=ascii
-
Convert
EBCDIC
to
ASCII.
- ebcdic
-
Convert
ASCII
to
EBCDIC.
- ibm
-
Slightly different map of
ASCII
to
EBCDIC.
- block
-
Convert variable length records to fixed length.
- unblock
-
Convert fixed length 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.
- arg, arg[,...]
-
Several comma-separated conversions, for a combination of
effects. For instance,
conv=sync,block
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
k
(kilobytes) to specify multiplication by 1024,
b
(blocks of 512 bytes) to specify multiplication by 512,
or
w
(words) to specify multiplication by 4;
a pair of numbers may be separated by
x
to indicate a product.
cbs
is used only if
ascii,
unblock,
ebcdic,
ibm,
or
block
conversion is specified. In the first two cases,
cbs
characters are placed into the conversion buffer, any specified
character mapping is done, trailing blanks trimmed and
NEWLINE
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
cbs.
After completion,
dd
reports the number of whole and partial input and output blocks.
EXAMPLES
To read an
EBCDIC
tape blocked ten 80-byte
EBCDIC
card images per record into the
ASCII
file
x:
example% dd if=/dev/rmt0 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 record sizes.
Sun386i EXAMPLES
The following write the file
filename
to a 3.5-inch floppy and read from the floppy into a file
filename,
respectively:
-
example% dd if=filename of=/dev/rfd0c bs=9k
example% dd if=/dev/rfd0c of=filename bs=9k
Sun386i files names are shown in
fdformat.1
SEE ALSO
cp.1
fdformat.1
tr.1v
DIAGNOSTICS
- f+p records in(out):
-
Numbers of full and partial records read(written).
BUGS
The
ASCII/EBCDIC
conversion tables are taken from the 256 character standard in the
CACM
Nov, 1968. The
ibm
conversion, while less blessed as a standard,
corresponds better to certain
IBM
print train conventions. There is no universal solution.
The
block
and
unblock
options cannot be combined with the
ascii,
ebcdic
or
ibm.
Invalid combinations
silently ignore all but the last mutually-exclusive keyword.
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97