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DD(1) General Commands Manual DD(1) NAME dd, dblbuf - convert and copy a file SYNOPSIS dd [ option=value ] dblbuf [ -b blocksize ] [ file ] DESCRIPTION Dd copies the specified input file to the specified output with possi- ble 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 if=file Set the input file (standard input by default). of=file Set the output file (standard output by default). ibs=n Set input block size to n bytes (default 512). obs=n Set output block size (default 512). bs=n Set both input and output block size, superseding ibs and 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. cbs=n Set conversion buffer size. skip=n Skip n input records before copying. iseek=n Seek n records forward on input file before copying. files=n Copy and concatenate n input files (makes sense only where in- put is a magnetic tape or similar device). oseek=n Aeek 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 Like ebcdic but with a slightly different character map. block Convert variable length ASCII records to fixed length. unblock Convert fixed length ASCII 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 bytes. Where sizes are specified, a number of bytes is expected. A number may end with or to specify multiplication by 1024, 512, or 2 respectively; a pair of numbers may be separated by to indicate a product. Multiple conversions may be specified in the style: is used only if or conversion is specified. In the first two cases, n characters are copied into the conversion buffer, any specified charac- ter 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 n. If is unspecified or zero, the and options convert the character set without changing the block structure of the input file; the and options become a simple file copy. Dblbuf copies the named file, or the standard input if no file is spec- ified, to the standard output. Output is written in blocks matching the input up to the given blocksize, or 32768 bytes if not specified. Dblbuf uses multiple processes to run faster, which is particularly useful in dealing with a device such as a streaming tape drive. EXAMPLES dd if=/dev/rmt0 of=x ibs=800 cbs=80 conv=ascii,lcase Read an EBCDIC tape blocked ten 80-byte EBCDIC card images per record into an ASCII file. Note the use of raw magtape to han- dle arbitrary record sizes. tar cf /dev/stdout /usr | dblbuf >/dev/rmt1 Copy the directory to tape on SEE ALSO cp(1), tar(1), cpio(1) DIAGNOSTICS Dd reports the number of full + partial input and output blocks han- dled. BUGS The ASCII/EBCDIC conversion tables for dd were taken from the 256-char- acter standard in CACM Nov, 1968. The conversion, while less blessed as a standard, corresponds better to certain IBM print train conven- tions. There is no universal solution. Options if and of are verbose equivalents of < and >. DD(1)