1DD(1) User Commands DD(1)
2
6 dd - convert and copy a file
7
9 dd [OPERAND]...
10 dd OPTION
11
13 Copy a file, converting and formatting according to the operands.
14 bs=BYTES
16 read and write up to BYTES bytes at a time (default: 512); over‐
17 rides ibs and obs
18 cbs=BYTES
20 convert BYTES bytes at a time
21 conv=CONVS
23 convert the file as per the comma separated symbol list
24 count=N
26 copy only N input blocks
27 ibs=BYTES
29 read up to BYTES bytes at a time (default: 512)
30 if=FILE
32 read from FILE instead of stdin
33 iflag=FLAGS
35 read as per the comma separated symbol list
36 obs=BYTES
38 write BYTES bytes at a time (default: 512)
39 of=FILE
41 write to FILE instead of stdout
42 oflag=FLAGS
44 write as per the comma separated symbol list
45 seek=N skip N obs-sized blocks at start of output
47 skip=N skip N ibs-sized blocks at start of input
49 status=LEVEL
51 The LEVEL of information to print to stderr; 'none' suppresses
52 everything but error messages, 'noxfer' suppresses the final
53 transfer statistics, 'progress' shows periodic transfer statis‐
54 tics
55 N and BYTES may be followed by the following multiplicative suffixes:
57 c=1, w=2, b=512, kB=1000, K=1024, MB=1000*1000, M=1024*1024, xM=M,
58 GB=1000*1000*1000, G=1024*1024*1024, and so on for T, P, E, Z, Y. Bi‐
59 nary prefixes can be used, too: KiB=K, MiB=M, and so on.
60 Each CONV symbol may be:
62 ascii from EBCDIC to ASCII
64 ebcdic from ASCII to EBCDIC
66 ibm from ASCII to alternate EBCDIC
68 block pad newline-terminated records with spaces to cbs-size
70 unblock
72 replace trailing spaces in cbs-size records with newline
73 lcase change upper case to lower case
75 ucase change lower case to upper case
77 sparse try to seek rather than write all-NUL output blocks
79 swab swap every pair of input bytes
81 sync pad every input block with NULs to ibs-size; when used with
83 block or unblock, pad with spaces rather than NULs
84 excl fail if the output file already exists
86 nocreat
88 do not create the output file
89 notrunc
91 do not truncate the output file
92 noerror
94 continue after read errors
95 fdatasync
97 physically write output file data before finishing
98 fsync likewise, but also write metadata
100 Each FLAG symbol may be:
102 append append mode (makes sense only for output; conv=notrunc sug‐
104 gested)
105 direct use direct I/O for data
107 directory
109 fail unless a directory
110 dsync use synchronized I/O for data
112 sync likewise, but also for metadata
114 fullblock
116 accumulate full blocks of input (iflag only)
117 nonblock
119 use non-blocking I/O
120 noatime
122 do not update access time
123 nocache
125 Request to drop cache. See also oflag=sync
126 noctty do not assign controlling terminal from file
128 nofollow
130 do not follow symlinks
131 count_bytes
133 treat 'count=N' as a byte count (iflag only)
134 skip_bytes
136 treat 'skip=N' as a byte count (iflag only)
137 seek_bytes
139 treat 'seek=N' as a byte count (oflag only)
140 Sending a USR1 signal to a running 'dd' process makes it print I/O sta‐
142 tistics to standard error and then resume copying.
143 Options are:
145 --help display this help and exit
147 --version
149 output version information and exit
150
152 Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
153
155 GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
156 Report any translation bugs to <https://translationproject.org/team/>
157
159 Copyright © 2021 Free Software Foundation, Inc. License GPLv3+: GNU
160 GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
161 This is free software: you are free to change and redistribute it.
162 There is NO WARRANTY, to the extent permitted by law.
163
165 Full documentation <https://www.gnu.org/software/coreutils/dd>
166 or available locally via: info '(coreutils) dd invocation'
167GNU coreutils 9.0 March 2022 DD(1)