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 read and write up to BYTES bytes at a time
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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 up to 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=N skip N obs-sized blocks at start of output
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47 skip=N skip N ibs-sized blocks at start of input
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49 status=LEVEL
50 The LEVEL of information to print to stderr; 'none' suppresses
51 everything but error messages, 'noxfer' suppresses the final
52 transfer statistics, 'progress' shows periodic transfer statis‐
53 tics
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55 N and BYTES may be followed by the following multiplicative suffixes: c
56 =1, w =2, b =512, kB =1000, K =1024, MB =1000*1000, M =1024*1024, xM =M
57 GB =1000*1000*1000, G =1024*1024*1024, and so on for 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 ucase change lower case to upper case
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76 sparse try to seek rather than write the output for NUL input blocks
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78 swab swap every pair of input bytes
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80 sync pad every input block with NULs to ibs-size; when used with
81 block or unblock, pad with spaces rather than NULs
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83 excl fail if the output file already exists
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85 nocreat
86 do not create the output file
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88 notrunc
89 do not truncate the output file
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91 noerror
92 continue after read errors
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94 fdatasync
95 physically write output file data before finishing
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97 fsync likewise, but also write metadata
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99 Each FLAG symbol may be:
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101 append append mode (makes sense only for output; conv=notrunc sug‐
102 gested)
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104 direct use direct I/O for data
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106 directory
107 fail unless a directory
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109 dsync use synchronized I/O for data
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111 sync likewise, but also for metadata
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113 fullblock
114 accumulate full blocks of input (iflag only)
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116 nonblock
117 use non-blocking I/O
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119 noatime
120 do not update access time
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122 nocache
123 discard cached data
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125 noctty do not assign controlling terminal from file
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127 nofollow
128 do not follow symlinks
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130 count_bytes
131 treat 'count=N' as a byte count (iflag only)
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133 skip_bytes
134 treat 'skip=N' as a byte count (iflag only)
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136 seek_bytes
137 treat 'seek=N' as a byte count (oflag only)
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139 Sending a USR1 signal to a running 'dd' process makes it print I/O sta‐
140 tistics to standard error and then resume copying.
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142 $ dd if=/dev/zero of=/dev/null& pid=$!
143 $ kill -USR1 $pid; sleep 1; kill $pid
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145 18335302+0 records in 18335302+0 records out 9387674624 bytes
146 (9.4 GB) copied, 34.6279 seconds, 271 MB/s
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148 Options are:
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150 --help display this help and exit
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152 --version
153 output version information and exit
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155 GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
156 Report dd translation bugs to <http://translationproject.org/team/>
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159 Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
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162 Copyright © 2013 Free Software Foundation, Inc. License GPLv3+: GNU
163 GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
164 This is free software: you are free to change and redistribute it.
165 There is NO WARRANTY, to the extent permitted by law.
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168 The full documentation for dd is maintained as a Texinfo manual. If
169 the info and dd programs are properly installed at your site, the com‐
170 mand
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172 info coreutils 'dd invocation'
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174 should give you access to the complete manual.
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178GNU coreutils 8.22 October 2018 DD(1)