1DD(1)                            User Commands                           DD(1)
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NAME

6       dd - convert and copy a file
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SYNOPSIS

9       dd [OPERAND]...
10       dd OPTION
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DESCRIPTION

13       Copy a file, converting and formatting according to the operands.
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15       bs=BYTES
16              read and write BYTES bytes at a time (also see ibs=,obs=)
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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 (default: 512)
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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 (default: 512)
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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: c =1, w =2,  b  =512,  kB  =1000,  K  =1024,  MB  =1000*1000,  M
56       =1024*1024,  xM =M GB =1000*1000*1000, G =1024*1024*1024, and so on for
57       T, P, E, 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
105              fail unless a directory
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107       dsync  use synchronized I/O for data
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109       sync   likewise, but also for metadata
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111       fullblock
112              accumulate full blocks of input (iflag only)
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114       nonblock
115              use non-blocking I/O
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117       noatime
118              do not update access time
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120       noctty do not assign controlling terminal from file
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122       nofollow
123              do not follow symlinks
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125       Sending a USR1 signal to a running `dd' process makes it print I/O sta‐
126       tistics to standard error and then resume copying.
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128              $ dd if=/dev/zero of=/dev/null& pid=$!
129              $ kill -USR1 $pid; sleep 1; kill $pid
130
131              18335302+0  records  in  18335302+0 records out 9387674624 bytes
132              (9.4 GB) copied, 34.6279 seconds, 271 MB/s
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134       Options are:
135
136       --help display this help and exit
137
138       --version
139              output version information and exit
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AUTHOR

142       Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
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REPORTING BUGS

145       Report dd bugs to bug-coreutils@gnu.org
146       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
147       General help using GNU software: <http://www.gnu.org/gethelp/>
148       Report dd translation bugs to <http://translationproject.org/team/>
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COPYRIGHT

151       Copyright © 2010 Free Software Foundation, Inc.   License  GPLv3+:  GNU
152       GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
153       This  is  free  software:  you  are free to change and redistribute it.
154       There is NO WARRANTY, to the extent permitted by law.
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SEE ALSO

157       The full documentation for dd is maintained as a  Texinfo  manual.   If
158       the  info and dd programs are properly installed at your site, the com‐
159       mand
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161              info coreutils 'dd invocation'
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163       should give you access to the complete manual.
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167GNU coreutils 8.5                November 2010                           DD(1)