term% cat index.txt DD(1) General Commands Manual DD(1)
NAME
dd - convert and copy a file
SYNOPSIS
dd [ option value ] ...
DESCRIPTION
Dd copies the specified input file to the specified output with possi‐
ble 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 simi‐
lar input device).
-oseek n
Seek n records from beginning of output file before copying.
-count n
Copy only n input records.
-trunc n
By default, dd truncates the output file when it opens it;
-trunc 0 opens it without truncation.
-quiet n
By default, dd prints the number of blocks read and written
once it is finished. -quiet 1 silences this summary.
-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 or to specify multiplication by 1024 or 512 respectively; a
pair of numbers may be separated by to indicate a product. Multiple
conversions may be specified in the style:
is used only if or conversion is specified. In the first two cases, n
characters are copied into the conversion buffer, any specified charac‐
ter 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 is unspecified or zero, the and
options convert the character set without changing the block structure
of the input file; the and options become a simple file copy.
SOURCE
/sys/src/cmd/dd.c
SEE ALSO
cp(1)
DIAGNOSTICS
Dd reports the number of full + partial input and output blocks han‐
dled.
DD(1)