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dd(1) [bsd man page]

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 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. option values if= input file name; standard input is default of= output file name; standard output is default ibs=n input block size n bytes (default 512) obs=n output block size (default 512) bs=n set both input and output block size, superseding ibs and obs; also, if no conversion is specified, it is particularly effi- cient since no copy need be done cbs=n conversion buffer size skip=n skip n input records before starting copy files=n copy n input files before terminating (makes sense only where input is a magtape or similar device). seek=n seek n records from beginning of output file before copying count=n copy only n input records conv=ascii convert EBCDIC to ASCII ebcdic convert ASCII to EBCDIC ibm slightly different map of ASCII to EBCDIC block convert variable length records to fixed length unblock convert fixed length 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 ... , ... several comma-separated conversions Where sizes are specified, a number of bytes is expected. A number may end with k, b or w to specify multiplication by 1024, 512, or 2 respectively; a pair of numbers may be separated by x to indicate a product. Cbs is used only if ascii, unblock, ebcdic, ibm, or block conversion is specified. In the first two cases, cbs characters are placed into the conversion buffer, any specified character mapping is done, trailing blanks trimmed and new-line added before sending the line to the output. In the latter three cases, characters are read into the conversion buffer, and blanks added to make up an output record of size cbs. After completion, dd reports the number of whole and partial input and output blocks. For example, to read an EBCDIC tape blocked ten 80-byte EBCDIC card images per record into the ASCII file x: dd if=/dev/rmt0 of=x ibs=800 cbs=80 conv=ascii,lcase Note the use of raw magtape. Dd is especially suited to I/O on the raw physical devices because it allows reading and writing in arbitrary record sizes. SEE ALSO
cp(1), tr(1) DIAGNOSTICS
f+p records in(out): numbers of full and partial records read(written) BUGS
The ASCII/EBCDIC conversion tables are taken from the 256 character standard in the CACM Nov, 1968. The `ibm' conversion, while less blessed as a standard, corresponds better to certain IBM print train conventions. There is no universal solution. One must specify ``conv=noerror,sync'' when copying raw disks with bad sectors to insure dd stays synchronized. Certain combinations of arguments to conv= are permitted. However, the block or unblock option cannot be combined with ascii, ebcdic or ibm. Invalid combinations silently ignore all but the last mutually-exclusive keyword. 4th Berkeley Distribution April 29, 1985 DD(1)

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dd(1)							      General Commands Manual							     dd(1)

Name
       dd - copy and convert data

Syntax
       dd [option = value...]

Description
       The  command copies an input file to an output with any requested conversions.  The command is especially suited to I/O on the raw physical
       devices because it allows reading and writing in arbitrary record sizes.

       After completion, reports the number of whole and partial input and output blocks.

       This utility supports EOT handling which allows the use of multiple media.  The utility prompts for the next volume when it encounters  the
       end of the current volume.

Options
       Where  sizes (n) are given for an option, the number may end with k for kilobytes (1024 bytes), b for blocks (512 bytes), or w for words (2
       bytes).	Also, two numbers may be separated by the character x to indicate a product.

       if=name		   Input file name.  The standard input is the default.

       of=name		   Output file name.  The standard output is the default.

       ibs=n		   Input block size, n bytes. The default is 512 bytes.  Some devices do not support greater than 65,535 bytes.

       obs=n		   Output block size, n bytes.	The default is 512 bytes.  Some devices do not support greater than 65,535 bytes.

       bs=n		   Set both input and output block size to n bytes, superseding ibs and obs.  Also, if bs is specified, the copy  is  more
			   efficient, since no blocking conversion is necessary.

       cbs=n		   Conversion buffer size, n bytes.  Use only if ascii, unblock, ebcdic, ibm, or block conversion is specified.  For ascii
			   and unblock, n characters are placed into the conversion buffer, any specified  character  mapping  is  done,  trailing
			   blanks are trimmed and new line added before sending the line to the output.  For ebcdic, ibm, or block, characters are
			   read into the conversion buffer, and blanks added to make an output record of size n bytes.

       skip=n		   Skip n input records before starting to copy.

       files=n		   Copy n input files before terminating.  This option is useful only when the input is a magnetic tape or similar device.

       seek=n		   Seek n records from beginning of output file before copying.

       rbuf=n		   Use n buffers for reading from those raw devices that support n-buffered I/O.  (See Section 4 to check whether  a  spe-
			   cific  device  supports  n-buffered	I/O.)	All n reads are started and each read must complete before the data can be
			   used.  This allows an n-buffered read-ahead on supported raw devices.

			   A default of eight read buffers are used if the read device supports n-buffered I/O and the write device does not.

			   The rbuf option cannot be used with the wbuf option.

       wbuf=n		   Use n buffers for writing from those raw devices that support n-buffered I/O.  (See Section 4 to check whether  a  spe-
			   cific  device  supports  n-buffered	I/O.)  Each write is started but not known to be complete until all n buffers have
			   been used.  (This allows an n-buffered write-behind on supported raw devices).

			   A default of eight write buffers are used if the write device supports n-buffered I/O.

			   The wbuf option cannot be used with the rbuf option.

       count=n		   Copy only n input records.

       conv=ascii	   Convert EBCDIC to ASCII.

       conv=ebcdic	   Convert ASCII to EBCDIC.

       conv=ibm 	   Slightly different map of ASCII to EBCDIC (see RESTRICTIONS).

       conv=block	   Convert variable length records to fixed length.

       conv=unblock	   Convert fixed length records to variable length.

       conv=lcase	   Map alphabetics to lower case.

       conv=ucase	   Map alphabetics to upper case.

       conv=swab	   Swap every pair of bytes.

       conv=noerror	   Do not stop processing on an error.

       conv=sync	   Pad every input record to ibs.

       conv=nomulti	   Disable multiple tape volumes.

       conv=sparse	   Create a sparse output file.

       conv=... , ...	   Include several arguments for the conv option, separated by commas (see example below).

Examples
       The following example shows how to read an EBCDIC tape blocked ten 80-byte EBCDIC card images per record into the ASCII file x:
       dd if=/dev/rmt0h of=x ibs=800 cbs=80 conv=ascii,lcase

       Note the use of raw magtape.  As noted in the DESCRIPTION, the command is especially suited to I/O on the raw physical devices  because	it
       allows reading and writing in arbitrary record sizes.

Restrictions
       The ASCII/EBCDIC conversion tables are taken from the 256-character standard in the Communications of the ACM, (R)November, 1968.

       The ibm conversion corresponds to certain IBM print train conventions.

       One must specify ``conv=noerror,sync'' when copying raw disks with bad sectors to ensure that dd stays synchronized.
       On  SCSI  tape devices when reading a multi-volume tape set the command will exit normally upon hitting EOT on any volume rather than auto-
       matically unloading the volume and prompting for the next volume as is normal. The user should load the next volume and issue  the  command
       anew.

Diagnostics
       f+p records in(out): numbers of full and partial records read(written)

See Also
       cp(1), tr(1), nbuf(4)

																	     dd(1)

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