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Top Forums Shell Programming and Scripting Need specific byte positions of a file Post 302361395 by aigles on Tuesday 13th of October 2009 06:03:30 AM
Old 10-13-2009
Another way using dd :
Code:
dd if=filename bs=1 skip=642362 count=8

An example with the following input file (which contains a single record)
Code:
[001][002][003][004][005][006][007][008][009][010][011][012][013][014][015][016]
[017][018][019][020][021][022][023][024][025][026][027][028][029][030][031][032]
[033][034][035][036][037][038][039][040][041][042][043][044][045][046][047][048]
[049][050][051][052][053][054][055][056][057][058][059][060][061][062][063][064]
[065][066][067][068][069][070][071][072][073][074][075][076][077][078][079][080]
[081][082][083][084][085][086][087][088][089][090][091][092][093][094][095][096]
[097][098][099][100][101][102][103][104][105][106][107][108][109][110][111][112]
[113][114][115][116][117][118][119][120][121][122][123][124][125][126][127][128]
[129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144]
[145][146][147][148][149][150][151][152][153][154][155][156][157][158][159][160]
[161][162][163][164][165][166][167][168][169][170][171][172][173][174][175][176]
[177][178][179][180][181][182][183][184][185][186][187][188][189][190][191][192]
[193][194][195][196][197][198][199]

To extract bytes from 501 to 510 :
Code:
> dd if=inputfile bs=1 skip=500 count=10 2>/dev/null
[101][102]>

As you can see there is no line terminator in the output.

Jean-Pierre.
 

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ISPRINT(3)						   BSD Library Functions Manual 						ISPRINT(3)

NAME
isprint -- printing character test (space character inclusive) LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <ctype.h> int isprint(int c); DESCRIPTION
The isprint() function tests for any printing character, including space (' '). The value of the argument must be representable as an unsigned char or the value of EOF. In the ASCII character set, this includes the following characters (with their numeric values shown in octal): 040 sp 041 ``!'' 042 ``"'' 043 ``#'' 044 ``$'' 045 ``%'' 046 ``&'' 047 ``''' 050 ``('' 051 ``)'' 052 ``*'' 053 ``+'' 054 ``,'' 055 ``-'' 056 ``.'' 057 ``/'' 060 ``0'' 061 ``1'' 062 ``2'' 063 ``3'' 064 ``4'' 065 ``5'' 066 ``6'' 067 ``7'' 070 ``8'' 071 ``9'' 072 ``:'' 073 ``;'' 074 ``<'' 075 ``='' 076 ``>'' 077 ``?'' 100 ``@'' 101 ``A'' 102 ``B'' 103 ``C'' 104 ``D'' 105 ``E'' 106 ``F'' 107 ``G'' 110 ``H'' 111 ``I'' 112 ``J'' 113 ``K'' 114 ``L'' 115 ``M'' 116 ``N'' 117 ``O'' 120 ``P'' 121 ``Q'' 122 ``R'' 123 ``S'' 124 ``T'' 125 ``U'' 126 ``V'' 127 ``W'' 130 ``X'' 131 ``Y'' 132 ``Z'' 133 ``['' 134 ``'' 135 ``]'' 136 ``^'' 137 ``_'' 140 ```'' 141 ``a'' 142 ``b'' 143 ``c'' 144 ``d'' 145 ``e'' 146 ``f'' 147 ``g'' 150 ``h'' 151 ``i'' 152 ``j'' 153 ``k'' 154 ``l'' 155 ``m'' 156 ``n'' 157 ``o'' 160 ``p'' 161 ``q'' 162 ``r'' 163 ``s'' 164 ``t'' 165 ``u'' 166 ``v'' 167 ``w'' 170 ``x'' 171 ``y'' 172 ``z'' 173 ``{'' 174 ``|'' 175 ``}'' 176 ``~'' RETURN VALUES
The isprint() function returns zero if the character tests false and returns non-zero if the character tests true. COMPATIBILITY
The 4.4BSD extension of accepting arguments outside of the range of the unsigned char type in locales with large character sets is considered obsolete and may not be supported in future releases. The iswprint() function should be used instead. SEE ALSO
ctype(3), iswprint(3), ascii(7) STANDARDS
The isprint() function conforms to ISO/IEC 9899:1990 (``ISO C90''). BSD
July 17, 2005 BSD
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