---
name: "uu-dd"
section: "1"
platform: "linux"
package: "uutils-coreutils"
version: "0.12.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/uu-dd"
---

# uu-dd(1)

Copy, and optionally convert, a file system resource

## NAME

dd - Copy, and optionally convert, a file system resource

## SYNOPSIS

**dd** \[OPERAND\]...\
 **dd** OPTION

## 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.

      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 \<complete\>+\<partial\>. 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 : convert 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 is 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

v(uutils coreutils) 0.12.0