Путеводитель по Руководству Linux

  User  |  Syst  |  Libr  |  Device  |  Files  |  Other  |  Admin  |  Head  |



   dd.1p    ( 1 )

конвертировать и копировать файл (convert and copy a file)

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.