1DD(1) User Commands DD(1)
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6 dd - convert and copy a file
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9 dd [OPERAND]...
10 dd OPTION
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13 Copy a file, converting and formatting according to the operands.
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15 bs=BYTES
16 force ibs=BYTES and obs=BYTES
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18 cbs=BYTES
19 convert BYTES bytes at a time
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21 conv=CONVS
22 convert the file as per the comma separated symbol list
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24 count=BLOCKS
25 copy only BLOCKS input blocks
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27 ibs=BYTES
28 read BYTES bytes at a time
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30 if=FILE
31 read from FILE instead of stdin
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33 iflag=FLAGS
34 read as per the comma separated symbol list
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36 obs=BYTES
37 write BYTES bytes at a time
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39 of=FILE
40 write to FILE instead of stdout
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42 oflag=FLAGS
43 write as per the comma separated symbol list
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45 seek=BLOCKS
46 skip BLOCKS obs-sized blocks at start of output
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48 skip=BLOCKS
49 skip BLOCKS ibs-sized blocks at start of input
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51 status=noxfer
52 suppress transfer statistics
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54 BLOCKS and BYTES may be followed by the following multiplicative suf‐
55 fixes: xM M, c 1, w 2, b 512, kB 1000, K 1024, MB 1000*1000, M
56 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E,
57 Z, Y.
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59 Each CONV symbol may be:
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61 ascii from EBCDIC to ASCII
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63 ebcdic from ASCII to EBCDIC
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65 ibm from ASCII to alternate EBCDIC
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67 block pad newline-terminated records with spaces to cbs-size
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69 unblock
70 replace trailing spaces in cbs-size records with newline
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72 lcase change upper case to lower case
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74 nocreat
75 do not create the output file
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77 excl fail if the output file already exists
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79 notrunc
80 do not truncate the output file
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82 ucase change lower case to upper case
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84 swab swap every pair of input bytes
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86 noerror
87 continue after read errors
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89 sync pad every input block with NULs to ibs-size; when used with
90 block or unblock, pad with spaces rather than NULs
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92 fdatasync
93 physically write output file data before finishing
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95 fsync likewise, but also write metadata
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97 Each FLAG symbol may be:
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99 append append mode (makes sense only for output; conv=notrunc sug‐
100 gested)
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102 direct use direct I/O for data
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104 directory fail unless a directory dsync use synchronized I/O
105 for data sync likewise, but also for metadata nonblock use
106 non-blocking I/O noatime do not update access time noctty
107 do not assign controlling terminal from file nofollow do not
108 follow symlinks
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110 Sending a USR1 signal to a running `dd' process makes it print I/O sta‐
111 tistics to standard error and then resume copying.
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113 $ dd if=/dev/zero of=/dev/null& pid=$!
114 $ kill -USR1 $pid; sleep 1; kill $pid
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116 18335302+0 records in 18335302+0 records out 9387674624 bytes
117 (9.4 GB) copied, 34.6279 seconds, 271 MB/s
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119 Options are:
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121 --help display this help and exit
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123 --version
124 output version information and exit
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127 Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
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130 Report bugs to <bug-coreutils@gnu.org>.
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133 Copyright © 2007 Free Software Foundation, Inc.
134 This is free software. You may redistribute copies of it under the
135 terms of the GNU General Public License
136 <http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the
137 extent permitted by law.
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140 The full documentation for dd is maintained as a Texinfo manual. If
141 the info and dd programs are properly installed at your site, the com‐
142 mand
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144 info dd
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146 should give you access to the complete manual.
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150GNU coreutils 6.9 March 2008 DD(1)