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 up to BYTES bytes at a time (default: 512); over‐
17              rides ibs and obs
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19       cbs=BYTES
20              convert BYTES bytes at a time
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22       conv=CONVS
23              convert the file as per the comma separated symbol list
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25       count=N
26              copy only N input blocks
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28       ibs=BYTES
29              read up to BYTES bytes at a time (default: 512)
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31       if=FILE
32              read from FILE instead of stdin
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34       iflag=FLAGS
35              read as per the comma separated symbol list
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37       obs=BYTES
38              write BYTES bytes at a time (default: 512)
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40       of=FILE
41              write to FILE instead of stdout
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43       oflag=FLAGS
44              write as per the comma separated symbol list
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46       seek=N skip N obs-sized blocks at start of output
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48       skip=N skip N ibs-sized blocks at start of input
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50       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
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56       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.
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61       Each CONV symbol may be:
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63       ascii  from EBCDIC to ASCII
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65       ebcdic from ASCII to EBCDIC
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67       ibm    from ASCII to alternate EBCDIC
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69       block  pad newline-terminated records with spaces to cbs-size
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71       unblock
72              replace trailing spaces in cbs-size records with newline
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74       lcase  change upper case to lower case
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76       ucase  change lower case to upper case
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78       sparse try to seek rather than write all-NUL output blocks
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80       swab   swap every pair of input bytes
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82       sync   pad every input block with NULs  to  ibs-size;  when  used  with
83              block or unblock, pad with spaces rather than NULs
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85       excl   fail if the output file already exists
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87       nocreat
88              do not create the output file
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90       notrunc
91              do not truncate the output file
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93       noerror
94              continue after read errors
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96       fdatasync
97              physically write output file data before finishing
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99       fsync  likewise, but also write metadata
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101       Each FLAG symbol may be:
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103       append append  mode  (makes  sense  only  for output; conv=notrunc sug‐
104              gested)
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106       direct use direct I/O for data
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108       directory
109              fail unless a directory
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111       dsync  use synchronized I/O for data
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113       sync   likewise, but also for metadata
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115       fullblock
116              accumulate full blocks of input (iflag only)
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118       nonblock
119              use non-blocking I/O
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121       noatime
122              do not update access time
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124       nocache
125              Request to drop cache.  See also oflag=sync
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127       noctty do not assign controlling terminal from file
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129       nofollow
130              do not follow symlinks
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132       count_bytes
133              treat 'count=N' as a byte count (iflag only)
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135       skip_bytes
136              treat 'skip=N' as a byte count (iflag only)
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138       seek_bytes
139              treat 'seek=N' as a byte count (oflag only)
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141       Sending a USR1 signal to a running 'dd' process makes it print I/O sta‐
142       tistics to standard error and then resume copying.
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144       Options are:
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146       --help display this help and exit
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148       --version
149              output version information and exit
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AUTHOR

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

155       GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
156       Report any translation bugs to <https://translationproject.org/team/>
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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.
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SEE ALSO

165       Full documentation <https://www.gnu.org/software/coreutils/dd>
166       or available locally via: info '(coreutils) dd invocation'
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170GNU coreutils 9.0                 March 2022                             DD(1)
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