z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

dd
Options
2. If this input block is smaller than the specified input block size, dd pads it to the
specified size with null bytes. When you also specify a block or unblock
conversion, dd uses spaces instead of null bytes.
3. If you specified bs=s and requested no conversion other than sync or noerror,
dd writes the padded (if necessary) input block to the output as a single block
and omits the remaining steps.
4. If you specified the swab conversion, dd swaps each pair of input bytes. If there
is an odd number of input bytes, dd does not attempt to swap the last byte.
5. dd performs all remaining conversions on the input data independently of the
input block boundaries. A fixed-length input or output record may span these
boundaries.
6. dd gathers the converted data into output blocks of the specified size. When dd
reaches the end of the input, it writes the remaining output as a block (without
padding if conv=sync is not specified). As a result, the final output block may be
shorter than the output block size.
bs=size
Sets both input and output block sizes to size bytes. You can suffix this
decimal number with w, b, k, or x number, to multiply it by 2, 512, 1024, or
number, respectively. You can also specify size as two decimal numbers
(with or without suffixes) separated by x to indicate the product of the two
values. Processing is faster when ibs and obs are equal, since this avoids
buffer copying. The default block size is 1B. bs=size supersedes any
settings of ibs=size or obs=size.
If you specify bs=size and you request no other conversions than noerror,
notrunc, or sync, dd writes the data from each input block as a separate
output block; if the input data is less than a full block and you did not
request sync conversion, the output block is the same size as the input
block.
cbs=size
Sets the size of the conversion buffer used by various conv options.
conv=conversion[, conversion, ...]
conversion can be any one of the following:
230 z/OS V1R9.0 UNIX System Services Command Reference
ascii Converts EBCDIC input to ASCII for output; it is provided for
compatibility purposes only.
To copy a file and convert between a shell code page and ASCII,
use iconv, not dd.
block Converts variable-length records to fixed-length records. dd treats
the input data as a sequence of variable-length records (each
terminated by a newline or an EOF character) independent of the
block boundaries. dd converts each input record by first removing
any newline characters and then padding (with spaces) or
truncating the record to the size of the conversion buffer. dd reports
the number of truncated records on standard error (stderr). You
must specify cbs=size with this conversion.
Note: When working with doublebyte characters, dd truncates the
record after the last complete doublebyte character that will
fit in the conversion buffer. dd then pads the record with
spaces if it is shorter than the conversion buffer size.