dd Command dd File conversion dd [option=value] ... dd copies an input file to an output file, while performing re- quested conversions. Options include case and character set con- versions, byte swapping conversion for other machines, and dif- ferent input and output buffer sizes. dd can be used with raw disk files or raw tape files to do efficient copies with large block (record) sizes. Read and write requests can be changed with the bs option described below. The following list gives each available option. Any numbers which specify block sizes or seek positions may be written in several ways. A number followed by w, b, or k is multiplied by two (for words), 512 (for blocks), or 1,024 (for kilobytes), respectively, to obtain the size in bytes. A pair of such num- bers separated by x is multiplied together to produce the size. All buffer sizes default to 512 bytes if not specified. bs=n Set the size of the buffer for both input and output to n bytes. cbs=n Set the conversion buffer size to n bytes (used only with character set conversions between ASCII and EBCDIC). conv=list Perform conversions specified by the comma-separated list, which may include the following: ascii Convert EBCDIC to ASCII. ebcdic Convert ASCII to EBCDIC. ibm Convert ASCII to EBCDIC, IBM flavor. lcase Convert upper case to lower. noerror Continue processing on I/O errors. swab Swap every pair of bytes before output. sync Pad input buffers with 0 bytes to size of ibs. ucase Convert lower case to upper. count=n Copy a maximum of n input records. files=n Copy a maximum of n input files (useful for multifile tapes). ibs=n Set the input buffer size to n (normally used if input and output blocking sizes are to be different). if=file Open file for input; the standard input is used when no if= option is given. COHERENT Lexicon Page 1
dd Command dd obs=n Set the output buffer size to n. of=file Open file for output; the standard output is used when no of= option is given. seek=n Seek to position n bytes into the output before copying (does not work on stream data such as tapes, com- munications devices, and pipes). skip=n Read and discard the first n input records. ***** See Also ***** ASCII, commands, conv, cp, tape, tr ***** Diagnostics ***** The command reports the number of full and partial buffers read and written upon completion. ***** Notes ***** Because of differing interpretations of EBCDIC, especially for certain more exotic graphic characters such as braces and back- slash, no one conversion table will be adequate for all ap- plications. The ebcdic table is the American Standard of the Business Equipment Manufacturers Association. The ibm table seems to be more practical for line printer codes at many IBM in- stallations. COHERENT Lexicon Page 2