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=N
25              copy only N 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=WHICH
52              WHICH info to suppress outputting to stderr; 'noxfer' suppresses
53              transfer stats, 'none' suppresses all
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55       BLOCKS and BYTES may be followed by the following  multiplicative  suf‐
56       fixes:  c  =1,  w  =2,  b  =512,  kB  =1000,  K =1024, MB =1000*1000, M
57       =1024*1024, xM =M GB =1000*1000*1000, G =1024*1024*1024, and so on  for
58       T, P, E, Z, Y.
59
60       Each CONV symbol may be:
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62       ascii  from EBCDIC to ASCII
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64       ebcdic from ASCII to EBCDIC
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66       ibm    from ASCII to alternate EBCDIC
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68       block  pad newline-terminated records with spaces to cbs-size
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70       unblock
71              replace trailing spaces in cbs-size records with newline
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73       lcase  change upper case to lower case
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75       nocreat
76              do not create the output file
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78       excl   fail if the output file already exists
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80       notrunc
81              do not truncate the output file
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83       ucase  change lower case to upper case
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85       sparse try to seek rather than write the output for NUL input blocks
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87       swab   swap every pair of input bytes
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89       noerror
90              continue after read errors
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92       sync   pad  every  input  block  with  NULs to ibs-size; when used with
93              block or unblock, pad with spaces rather than NULs
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95       fdatasync
96              physically write output file data before finishing
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98       fsync  likewise, but also write metadata
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100       Each FLAG symbol may be:
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102       append append mode (makes sense  only  for  output;  conv=notrunc  sug‐
103              gested)
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105       direct use direct I/O for data
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107       directory
108              fail unless a directory
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110       dsync  use synchronized I/O for data
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112       sync   likewise, but also for metadata
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114       fullblock
115              accumulate full blocks of input (iflag only)
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117       nonblock
118              use non-blocking I/O
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120       noatime
121              do not update access time
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123       noctty do not assign controlling terminal from file
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125       nofollow
126              do not follow symlinks
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128       count_bytes
129              treat 'count=N' as a byte count (iflag only)
130
131       Sending a USR1 signal to a running `dd' process makes it print I/O sta‐
132       tistics to standard error and then resume copying.
133
134              $ dd if=/dev/zero of=/dev/null& pid=$!
135              $ kill -USR1 $pid; sleep 1; kill $pid
136
137              18335302+0 records in 18335302+0 records  out  9387674624  bytes
138              (9.4 GB) copied, 34.6279 seconds, 271 MB/s
139
140       Options are:
141
142       --help display this help and exit
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144       --version
145              output version information and exit
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AUTHOR

148       Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
149

REPORTING BUGS

151       Report dd bugs to bug-coreutils@gnu.org
152       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
153       General help using GNU software: <http://www.gnu.org/gethelp/>
154       Report dd translation bugs to <http://translationproject.org/team/>
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157       Copyright  ©  2010  Free Software Foundation, Inc.  License GPLv3+: GNU
158       GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
159       This is free software: you are free  to  change  and  redistribute  it.
160       There is NO WARRANTY, to the extent permitted by law.
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SEE ALSO

163       The  full  documentation  for dd is maintained as a Texinfo manual.  If
164       the info and dd programs are properly installed at your site, the  com‐
165       mand
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167              info coreutils 'dd invocation'
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169       should give you access to the complete manual.
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173GNU coreutils 8.4                  June 2018                             DD(1)
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