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.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.50.1.
.TH DD "1" "February 2026" "GNU coreutils 9.10" "User Commands"
.SH NAME
dd \- convert and copy a file
.SH SYNOPSIS
.B dd
[\fI\,OPERAND\/\fR]...
.br
.B dd
\fI\,OPTION\/\fR
.SH DESCRIPTION
.\" Add any additional description here
.PP
Copy a file, converting and formatting according to the operands.
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddbs'\fBbs=BYTES\fP\X'tty: link'
read and write up to BYTES bytes at a time (default: 512);
overrides ibs and obs
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddcbs'\fBcbs=BYTES\fP\X'tty: link'
convert BYTES bytes at a time
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddconv'\fBconv=CONVS\fP\X'tty: link'
convert the file as per the comma separated symbol list
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddcount'\fBcount=N\fP\X'tty: link'
copy only N input blocks
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddibs'\fBibs=BYTES\fP\X'tty: link'
read up to BYTES bytes at a time (default: 512)
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddif'\fBif=FILE\fP\X'tty: link'
read from FILE instead of standard input
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddiflag'\fBiflag=FLAGS\fP\X'tty: link'
read as per the comma separated symbol list
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddobs'\fBobs=BYTES\fP\X'tty: link'
write BYTES bytes at a time (default: 512)
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddof'\fBof=FILE\fP\X'tty: link'
write to FILE instead of standard output
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddoflag'\fBoflag=FLAGS\fP\X'tty: link'
write as per the comma separated symbol list
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddseek'\fBseek=N\fP\X'tty: link'
(or oseek=N) skip N obs sized output blocks
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddskip'\fBskip=N\fP\X'tty: link'
(or iseek=N) skip N ibs sized input blocks
.TP
\X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#ddstatus'\fBstatus=LEVEL\fP\X'tty: link'
The LEVEL of information to print to standard error;
\&'none' suppresses everything but error messages,
\&'noxfer' suppresses the final transfer statistics,
\&'progress' shows periodic transfer statistics
.PP
N and BYTES may be followed by the following multiplicative suffixes:
c=1, w=2, b=512, kB=1000, K=1024, MB=1000*1000, M=1024*1024, xM=M,
GB=1000*1000*1000, G=1024*1024*1024, and so on for T, P, E, Z, Y, R, Q.
Binary prefixes can be used, too: KiB=K, MiB=M, and so on.
If N ends in 'B', it counts bytes not blocks.
.PP
Each CONV symbol may be:
.TP
ascii
from EBCDIC to ASCII
.TP
ebcdic
from ASCII to EBCDIC
.TP
ibm
from ASCII to alternate EBCDIC
.TP
block
pad newline\-terminated records with spaces to cbs\-size
.TP
unblock
replace trailing spaces in cbs\-size records with newline
.TP
lcase
change upper case to lower case
.TP
ucase
change lower case to upper case
.TP
sparse
try to seek rather than write all\-NUL output blocks
.TP
swab
swap every pair of input bytes
.TP
sync
pad every input block with NULs to ibs\-size; when used
with block or unblock, pad with spaces rather than NULs
.TP
excl
fail if the output file already exists
.TP
nocreat
do not create the output file
.TP
notrunc
do not truncate the output file
.TP
noerror
continue after read errors
.TP
fdatasync
physically write output file data before finishing
.TP
fsync
likewise, but also write metadata
.PP
Each FLAG symbol may be:
.TP
append
append mode (makes sense only for output; conv=notrunc suggested)
.TP
direct
use direct I/O for data
.TP
directory
fail unless a directory
.TP
dsync
use synchronized I/O for data
.TP
sync
likewise, but also for metadata
.TP
fullblock
accumulate full blocks of input (iflag only)
.TP
nonblock
use non\-blocking I/O
.TP
noatime
do not update access time
.TP
nocache
Request to drop cache. See also oflag=sync
.TP
noctty
do not assign controlling terminal from file
.TP
nofollow
do not follow symlinks
.PP
Sending a USR1 signal to a running 'dd' process makes it
print I/O statistics to standard error and then resume copying.
.PP
Options are:
.TP
\X'tty: link https://www.gnu.org/software/coreutils/dd#dd--help'\fB\-\-help\fP\X'tty: link'
display this help and exit
.TP
\X'tty: link https://www.gnu.org/software/coreutils/dd#dd--version'\fB\-\-version\fP\X'tty: link'
output version information and exit
.SH AUTHOR
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
.SH "REPORTING BUGS"
Report bugs to: bug\-coreutils@gnu.org
.br
GNU coreutils home page: <https://www.gnu.org/software/coreutils/>
.br
General help using GNU software: <https://www.gnu.org/gethelp/>
.br
Report any translation bugs to <https://translationproject.org/team/>
.SH COPYRIGHT
Copyright \(co 2026 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
.br
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
.SH "SEE ALSO"
Full documentation <https://www.gnu.org/software/coreutils/dd>
.br
or available locally via: info \(aq(coreutils) dd invocation\(aq
|
