dd(1) General Commands Manual dd(1) NAME dd - Copy, and optionally convert, a file system resource SYNOPSIS dd [-h|--help] [-V|--version] [operands] DESCRIPTION Copy, and optionally convert, a file system resource OPTIONS -h, --help Print help -V, --version Print version [operands] EXTRA ### Operands - bs=BYTES : read and write up to BYTES bytes at a time (default: 512); overwrites ibs and obs. - cbs=BYTES : the 'conversion block size' in bytes. Applies to the conv=block, and conv=unblock operations. - conv=CONVS : a comma-separated list of conversion options or (for legacy reasons) file flags. - count=N : stop reading input after N ibs-sized read operations rather than proceeding until EOF. See iflag=count_bytes if stopping after N bytes is preferred - ibs=N : the size of buffer used for reads (default: 512) - if=FILE : the file used for input. When not specified, stdin is used instead - iflag=FLAGS : a comma-separated list of input flags which specify how the input source is treated. FLAGS may be any of the input-flags or general-flags specified below. - skip=N (or iseek=N) : skip N ibs-sized records into input before beginning copy/convert operations. See iflag=seek_bytes if seeking N bytes is preferred. - obs=N : the size of buffer used for writes (default: 512) - of=FILE : the file used for output. When not specified, stdout is used instead - oflag=FLAGS : comma separated list of output flags which specify how the output source is treated. FLAGS may be any of the output flags or general flags specified below - seek=N (or oseek=N) : seeks N obs-sized records into output before beginning copy/convert operations. See oflag=seek_bytes if seeking N bytes is preferred - status=LEVEL : controls whether volume and performance stats are written to stderr. When unspecified, dd will print stats upon completion. An example is below. plain 6+0 records in 16+0 records out 8192 bytes (8.2 kB, 8.0 KiB) copied, 0.00057009 s, 14.4 MB/s The first two lines are the 'volume' stats and the final line is the 'performance' stats. The volume stats indicate the number of complete and partial ibs-sized reads, or obs-sized writes that took place during the copy. The format of the volume stats is +. If records have been truncated (see conv=block), the volume stats will contain the number of truncated records. Possible LEVEL values are: - progress : Print periodic performance stats as the copy proceeds. - noxfer : Print final volume stats, but not performance stats. - none : Do not print any stats. Printing performance stats is also triggered by the INFO signal (where supported), or the USR1 signal. Setting the POSIXLY_CORRECT environment variable to any value (including an empty value) will cause the USR1 signal to be ignored. ### Conversion Options - ascii : convert from EBCDIC to ASCII. This is the inverse of the ebcdic option. Implies conv=unblock. - ebcdic : convert from ASCII to EBCDIC. This is the inverse of the ascii option. Implies conv=block. - ibm : convert from ASCII to EBCDIC, applying the conventions for [, ] and ~ specified in POSIX. Implies conv=block. - ucase : convert from lower-case to upper-case. - lcase : converts from upper-case to lower-case. - block : for each newline less than the size indicated by cbs=BYTES, remove the newline and pad with spaces up to cbs. Lines longer than cbs are truncated. - unblock : for each block of input of the size indicated by cbs=BYTES, remove right-trailing spaces and replace with a newline character. - sparse : attempts to seek the output when an obs-sized block consists of only zeros. - swab : swaps each adjacent pair of bytes. If an odd number of bytes is present, the final byte is omitted. - sync : pad each ibs-sided block with zeros. If block or unblock is specified, pad with spaces instead. - excl : the output file must be created. Fail if the output file is already present. - nocreat : the output file will not be created. Fail if the output file in not already present. - notrunc : the output file will not be truncated. If this option is not present, output will be truncated when opened. - noerror : all read errors will be ignored. If this option is not present, dd will only ignore Error::Interrupted. - fdatasync : data will be written before finishing. - fsync : data and metadata will be written before finishing. ### Input flags - count_bytes : a value to count=N will be interpreted as bytes. - skip_bytes : a value to skip=N will be interpreted as bytes. - fullblock : wait for ibs bytes from each read. zero-length reads are still considered EOF. ### Output flags - append : open file in append mode. Consider setting conv=notrunc as well. - seek_bytes : a value to seek=N will be interpreted as bytes. ### General Flags - direct : use direct I/O for data. - directory : fail unless the given input (if used as an iflag) or output (if used as an oflag) is a directory. - dsync : use synchronized I/O for data. - sync : use synchronized I/O for data and metadata. - nonblock : use non-blocking I/O. - noatime : do not update access time. - nocache : request that OS drop cache. - noctty : do not assign a controlling tty. - nofollow : do not follow system links. VERSION v0.0.26 dd 0.0.26 dd(1)