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193 lines
3.4 KiB
Plaintext
193 lines
3.4 KiB
Plaintext
.TH DD 1
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.SH NAME
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dd \- convert and copy a file
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.SH SYNOPSIS
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.B dd
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[option=value] ...
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.SH DESCRIPTION
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.I Dd
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copies the specified input file
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to the specified output with
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possible conversions.
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The standard input and output are used by default.
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The input and output block size may be
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specified to take advantage of raw physical I/O.
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.PP
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.br
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.ns
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.TP 15
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.I option
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.I values
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.br
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.ns
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.TP
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if=
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input file name; standard input is default
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.br
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.ns
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.TP
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of=
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output file name; standard output is default
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.br
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.ns
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.TP
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.RI ibs= n
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input block size
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.I n
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bytes (default 512)
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.br
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.ns
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.TP
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.RI obs= n
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output block size (default 512)
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.br
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.ns
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.TP
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.RI bs= n
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set both input and output block size,
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superseding
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.I ibs
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and
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.I obs;
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also, if no conversion is specified,
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it is particularly efficient since no copy need be done
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.br
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.ns
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.TP
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.RI cbs= n
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conversion buffer size
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.br
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.ns
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.TP
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.RI skip= n
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skip
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.IR n ""
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input records before starting copy
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.br
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.ns
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.TP
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.RI files= n
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copy
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.I n
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files from (tape) input
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.br
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.ns
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.TP
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.RI seek= n
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seek
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.I n
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records from beginning of output file before copying
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.br
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.ns
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.TP
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count=\fIn\fR
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copy only
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.IR n ""
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input records
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.br
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.ns
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.TP
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conv=ascii
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.ds h \h'\w'conv='u'
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convert EBCDIC to ASCII
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.br
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.ns
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.IP \*hebcdic
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convert ASCII to EBCDIC
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.br
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.ns
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.IP \*hibm
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slightly different map of ASCII to EBCDIC
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.br
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.ns
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.IP \*hlcase
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map alphabetics to lower case
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.br
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.ns
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.IP \*hucase
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map alphabetics to upper case
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.br
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.ns
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.IP \*hswab
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swap every pair of bytes
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.br
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.ns
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.IP \*hnoerror
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do not stop processing on an error
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.br
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.ns
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.IP \*hsync
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pad every input record to
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.I ibs
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.br
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.ns
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.IP "\*h... , ..."
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several comma-separated conversions
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.PP
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.fi
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Where sizes are specified,
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a number of bytes is expected.
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A number may end with
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.B "k, b"
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or
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.B w
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to specify multiplication by
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1024, 512, or 2 respectively;
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a pair of numbers may be separated by
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.B x
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to indicate a product.
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.PP
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.I Cbs
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is used only if
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.I ascii
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or
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.I ebcdic
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conversion is specified.
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In the former case
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.I cbs
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characters are placed into the conversion buffer, converted to
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ASCII, and trailing blanks trimmed and new-line added
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before sending the line to the output.
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In the latter case ASCII characters are read into the
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conversion buffer, converted to EBCDIC, and blanks added
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to make up an
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output record of size
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.IR cbs .
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.PP
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After completion,
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.I dd
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reports the number of whole and partial input and output
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blocks.
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.PP
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For example, to read an EBCDIC tape blocked ten 80-byte
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EBCDIC card images per record into the ASCII file
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.IR x :
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.IP ""
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dd if=/dev/rmt0 of=x ibs=800 cbs=80 conv=ascii,lcase
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.PP
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Note the use of raw magtape.
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.I Dd
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is especially suited to I/O on the raw
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physical devices because it allows reading
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and writing in arbitrary record sizes.
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.PP
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To skip over a file before copying from magnetic tape do
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.IP""
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(dd of=/dev/null; dd of=x) </dev/rmt0
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.SH "SEE ALSO"
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cp(1), tr(1)
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.SH DIAGNOSTICS
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f+p records in(out): numbers of full and partial records read(written)
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.SH BUGS
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The ASCII/EBCDIC conversion tables are
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taken
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from the 256 character standard in
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the CACM Nov, 1968.
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The `ibm' conversion, while less blessed as a standard,
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corresponds better to certain IBM print train conventions.
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There is no universal solution.
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.PP
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Newlines are inserted only on conversion to ASCII;
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padding is done only on conversion to EBCDIC.
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These should be separate options.
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