NAME
dd – convert and copy a 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. 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.
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 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.

SOURCE
/sys/src/cmd/dd.c

SEE ALSO
cp(1)

DIAGNOSTICS
Dd reports the number of full + partial input and output blocks handled.