.TH DD 1
.CT 1 files comm_dev
.SH NAME
dd, dblbuf \- convert and copy a file
.SH SYNOPSIS
.B dd
[
.I option=value
]
...
.PP
.B dblbuf
[
.B -b
.I blocksize
]
[
.I file
]
.SH DESCRIPTION
.I 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
.TP \w'\f5count=\ \fIn'u
.BI if= file\^
Set the input file (standard input by default).
.TP
.BI of= file\^
Set the output file (standard output by default).
.TP
.BI ibs= n\^
Set input block size to
.I n\^
bytes (default 512).
.TP
.BI obs= n\^
Set output block size (default 512).
.TP
.BI bs= n\^
Set both input and output block size,
superseding
.I ibs\^
and
.IR 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.
.TP
.BI cbs= n\^
Set conversion buffer size.
.TP
.BI skip= n\^
Skip
.I n
input records before copying.
.TP
.BI iseek= n\^
Seek
.I n
records forward on input file
before copying.
.TP
.BI files= n\^
Copy and concatenate
.I n 
input files (makes sense only
where input is a magnetic tape or similar device).
.TP
.BI oseek= n\^
Aeek
.I n\^
records from beginning of output file before copying.
.TP
.BI count= n\^
Copy only
.I n
input records.
.HP
\f5conv=ascii\ \ \ \ \fRConvert \s-2EBCDIC\s0 to \s-2ASCII\s0.
.PD0
.RS "\w'\f5conv=\fP'u"
.TP "\w'\f5unblock\ \ \fP'u"
.B ebcdic
Convert
.SM ASCII
to
.SM EBCDIC.
.TP
.B ibm
Like
.B ebcdic
but with a slightly different character map.
.TP
.B block
Convert variable length
.SM ASCII
records to fixed length.
.TP
.B unblock
Convert fixed length
.SM ASCII
records to variable length.
.TP
.B lcase
Map alphabetics to lower case.
.TP
.B ucase
Map alphabetics to upper case.
.TP
.B swab
Swap every pair of bytes.
.TP
.B noerror
Do not stop processing on an error.
.TP
.B sync
Pad every input record to
.I  ibs\^
bytes.
.RE
.PD
.PP
.fi
Where sizes are specified,
a number of bytes is expected.
A number may end with
.LR k ,
.LR b ,
or
.L w
to specify multiplication by
1024, 512, or 2 respectively;
a pair of numbers may be separated by
.L x
to indicate a product.
Multiple conversions may be specified in the style:
.LR conv=ebcdic,ucase .
.PP
.L Cbs\^
is used only if
.LR ascii\^ ,
.LR unblock\^ ,
.LR ebcdic\^ ,
.LR ibm\^ ,
or
.L block\^
conversion is specified.
In the first two cases,
.I 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
.I n.
If
.L cbs\^
is unspecified or zero, the
.LR ascii\^ ,
.LR ebcdic\^ ,
and
.L ibm\^
options convert the character set without changing the block
structure of the input file; the
.L unblock\^
and
.L block\^
options become a simple file copy.
.PP
.I Dblbuf
copies the named
.IR file ,
or the standard input if no file
is specified, to the standard output.
Output is written in blocks matching the
input up to the given blocksize, or 32768
bytes if not specified.
.PP
.I Dblbuf
uses multiple processes
to run faster, which is particularly useful in dealing with
a device such as a streaming tape drive.
.SH EXAMPLES
.TP
.L
dd  if=/dev/rmt0  of=x  ibs=800  cbs=80  conv=ascii,lcase
Read an
.SM EBCDIC
tape blocked ten 80-byte
.SM EBCDIC
card images per record into an
.SM ASCII
file.
Note the use of raw magtape to handle arbitrary record sizes.
.TP
.L
tar cf /dev/stdout /usr | dblbuf >/dev/rmt1
Copy the
.F /usr
directory to tape on
.FR /dev/rmt1 .
.SH "SEE ALSO"
.IR cp (1), 
.IR tar (1), 
.IR cpio (1)
.SH DIAGNOSTICS
.I Dd
reports the number of full + partial input and output
blocks handled.
.SH BUGS
The
.SM ASCII/EBCDIC
conversion tables for
.I dd
were taken
from the 256-character standard in
.SM CACM
Nov, 1968.
The
.L ibm\^
conversion, while less blessed as a standard,
corresponds better to certain
.SM IBM
print train conventions.
There is no universal solution.
.br
Options
.B if
and
.B of
are verbose equivalents of
.B <
and
.BR > .