`dd': Convert and copy a file ============================= `dd' copies a file (from standard input to standard output, by default) with a changeable I/O block size, while optionally performing conversions on it. Synopsis: dd [OPTION]... The program accepts the following options. Also see Note: Common options. The numeric-valued options below (BYTES and BLOCKS) can be followed by a multiplier: `b'=512, `c'=1, `w'=2, `xM'=M, or any of the standard block size suffixes like `k'=1024 (Note: Block size). Use different `dd' invocations to use different block sizes for skipping and I/O. For example, the following shell commands copy data in 512 kB blocks between a disk and a tape, but do not save or restore a 4 kB label at the start of the disk: disk=/dev/rdsk/c0t1d0s2 tape=/dev/rmt/0 # Copy all but the label from disk to tape. (dd bs=4k skip=1 count=0 && dd bs=512k) <$disk >$tape # Copy from tape back to disk, but leave the disk label alone. (dd bs=4k seek=1 count=0 && dd bs=512k) <$tape >$disk `if=FILE' Read from FILE instead of standard input. `of=FILE' Write to FILE instead of standard output. Unless `conv=notrunc' is given, `dd' truncates FILE to zero bytes (or the size specified with `seek='). `ibs=BYTES' Read BYTES bytes at a time. `obs=BYTES' Write BYTES bytes at a time. `bs=BYTES' Both read and write BYTES bytes at a time. This overrides `ibs' and `obs'. `cbs=BYTES' Convert BYTES bytes at a time. `skip=BLOCKS' Skip BLOCKS `ibs'-byte blocks in the input file before copying. `seek=BLOCKS' Skip BLOCKS `obs'-byte blocks in the output file before copying. `count=BLOCKS' Copy BLOCKS `ibs'-byte blocks from the input file, instead of everything until the end of the file. `conv=CONVERSION[,CONVERSION]...' Convert the file as specified by the CONVERSION argument(s). (No spaces around any comma(s).) Conversions: `ascii' Convert EBCDIC to ASCII. `ebcdic' Convert ASCII to EBCDIC. `ibm' Convert ASCII to alternate EBCDIC. `block' For each line in the input, output `cbs' bytes, replacing the input newline with a space and padding with spaces as necessary. `unblock' Replace trailing spaces in each `cbs'-sized input block with a newline. `lcase' Change uppercase letters to lowercase. `ucase' Change lowercase letters to uppercase. `swab' Swap every pair of input bytes. GNU `dd', unlike others, works when an odd number of bytes are read--the last byte is simply copied (since there is nothing to swap it with). `noerror' Continue after read errors. `notrunc' Do not truncate the output file. `sync' Pad every input block to size of `ibs' with trailing zero bytes. When use with `block' or `unblock', pad with spaces instead of zero bytes.
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