конвертировать и копировать файл (convert and copy a file)
Имя (Name)
dd — convert and copy a file
Синопсис (Synopsis)
dd [operand...]
Описание (Description)
The dd utility shall copy the specified input file to the
specified output file with possible conversions using specific
input and output block sizes. It shall read the input one block
at a time, using the specified input block size; it shall then
process the block of data actually returned, which could be
smaller than the requested block size. It shall apply any
conversions that have been specified and write the resulting data
to the output in blocks of the specified output block size. If
the bs=expr operand is specified and no conversions other than
sync, noerror, or notrunc are requested, the data returned from
each input block shall be written as a separate output block; if
the read returns less than a full block and the sync conversion
is not specified, the resulting output block shall be the same
size as the input block. If the bs=expr operand is not specified,
or a conversion other than sync, noerror, or notrunc is
requested, the input shall be processed and collected into full-
sized output blocks until the end of the input is reached.
The processing order shall be as follows:
1. An input block is read.
2. If the input block is shorter than the specified input block
size and the sync conversion is specified, null bytes shall
be appended to the input data up to the specified size. (If
either block or unblock is also specified, <space> characters
shall be appended instead of null bytes.) The remaining
conversions and output shall include the pad characters as if
they had been read from the input.
3. If the bs=expr operand is specified and no conversion other
than sync or noerror is requested, the resulting data shall
be written to the output as a single block, and the remaining
steps are omitted.
4. If the swab conversion is specified, each pair of input data
bytes shall be swapped. If there is an odd number of bytes in
the input block, the last byte in the input record shall not
be swapped.
5. Any remaining conversions (block, unblock, lcase, and ucase)
shall be performed. These conversions shall operate on the
input data independently of the input blocking; an input or
output fixed-length record may span block boundaries.
6. The data resulting from input or conversion or both shall be
aggregated into output blocks of the specified size. After
the end of input is reached, any remaining output shall be
written as a block without padding if conv=sync is not
specified; thus, the final output block may be shorter than
the output block size.
