text-utils/hexdump.1

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  32 .\"     @(#)hexdump.1   8.2 (Berkeley) 4/18/94
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  34 .TH HEXDUMP "1" "April 2013" "util-linux" "User Commands"
  35 .SH NAME
  36 hexdump \- display file contents in hexadecimal, decimal, octal, or ascii
  37 .SH SYNOPSIS
  38 .B hexdump
  39 .RI [options] " file" ...
  40 .SH DESCRIPTION
  41 The
  42 .B hexdump
  43 utility is a filter which displays the specified files, or
  44 standard input if no files are specified, in a user-specified
  45 format.
  46 .SH OPTIONS
  47 Below, the \fIlength\fR and \fIoffset\fR arguments may be followed by the multiplicative
  48 suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB
  49 (the "iB" is optional, e.g. "K" has the same meaning as "KiB"), or the suffixes
  50 KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
  51 .TP
  52 \fB\-b\fR, \fB\-\-one\-byte\-octal\fR
  53 \fIOne-byte octal display\fR.  Display the input offset in hexadecimal,
  54 followed by sixteen space-separated, three-column, zero-filled bytes of input
  55 data, in octal, per line.
  56 .TP
  57 \fB\-c\fR, \fB\-\-one\-byte\-char\fR
  58 \fIOne-byte character display\fR.  Display the input offset in hexadecimal,
  59 followed by sixteen space-separated, three-column, space-filled characters of
  60 input data per line.
  61 .TP
  62 \fB\-C\fR, \fB\-\-canonical\fR
  63 \fICanonical hex+ASCII display\fR.  Display the input offset in hexadecimal,
  64 followed by sixteen space-separated, two-column, hexadecimal bytes, followed
  65 by the same sixteen bytes in
  66 .B %_p
  67 format enclosed in
  68 .RB ' | '
  69 characters.
  70 .TP
  71 \fB\-d\fR, \fB\-\-two\-bytes\-decimal\fR
  72 \fITwo-byte decimal display\fR.  Display the input offset in hexadecimal,
  73 followed by eight space-separated, five-column, zero-filled, two-byte units
  74 of input data, in unsigned decimal, per line.
  75 .TP
  76 \fB\-e\fR, \fB\-\-format\fR \fIformat_string\fR
  77 Specify a format string to be used for displaying data.
  78 .TP
  79 \fB\-f\fR, \fB\-\-format\-file\fR \fIfile\fR
  80 Specify a file that contains one or more newline-separated format strings.
  81 Empty lines and lines whose first non-blank character is a hash mark (\&#)
  82 are ignored.
  83 .TP
  84 \fB\-L\fR, \fB\-\-color\fR[=\fIwhen\fR]
  85 Accept color units for the output.  The optional argument \fIwhen\fP
  86 can be \fBauto\fR, \fBnever\fR or \fBalways\fR.  If the \fIwhen\fR argument is omitted,
  87 it defaults to \fBauto\fR.  The colors can be disabled; for the current built-in default
  88 see the \fB\-\-help\fR output.  See also the \fBColors\fR subsection and
  89 the \fBCOLORS\fR section below.
  90 .TP
  91 \fB\-n\fR, \fB\-\-length\fR \fIlength\fR
  92 Interpret only
  93 .I length
  94 bytes of input.
  95 .TP
  96 \fB\-o\fR, \fB\-\-two\-bytes\-octal\fR
  97 \fITwo-byte octal display\fR.  Display the input offset in hexadecimal,
  98 followed by eight space-separated, six-column, zero-filled, two-byte
  99 quantities of input data, in octal, per line.
 100 .TP
 101 \fB\-s\fR, \fB\-\-skip\fR \fIoffset\fR
 102 Skip
 103 .I offset
 104 bytes from the beginning of the input.
 105 .TP
 106 \fB\-v\fR, \fB\-\-no\-squeezing\fR
 107 The
 108 .B \-v
 109 option causes
 110 .B hexdump
 111 to display all input data.  Without the
 112 .B \-v
 113 option, any number of groups of output lines which would be identical to the
 114 immediately preceding group of output lines (except for the input offsets),
 115 are replaced with a line comprised of a single asterisk.
 116 .TP
 117 \fB\-x\fR, \fB\-\-two\-bytes\-hex\fR
 118 \fITwo-byte hexadecimal display\fR.  Display the input offset in hexadecimal,
 119 followed by eight space-separated, four-column, zero-filled, two-byte
 120 quantities of input data, in hexadecimal, per line.
 121 .TP
 122 .BR \-V , " \-\-version"
 123 Display version information and exit.
 124 .TP
 125 .BR \-h , " \-\-help"
 126 Display help text and exit.
 127 .PP
 128 For each input file,
 129 .B hexdump
 130 sequentially copies the input to standard output, transforming the data
 131 according to the format strings specified by the
 132 .B \-e
 133 and
 134 .B \-f
 135 options, in the order that they were specified.
 136 .SH FORMATS
 137 A format string contains any number of format units, separated by whitespace.
 138 A format unit contains up to three items: an iteration count, a byte count,
 139 and a format.
 140 .PP
 141 The iteration count is an optional positive integer, which defaults to one.
 142 Each format is applied iteration count times.
 143 .PP
 144 The byte count is an optional positive integer.  If specified it defines the
 145 number of bytes to be interpreted by each iteration of the format.
 146 .PP
 147 If an iteration count and/or a byte count is specified, a single slash must
 148 be placed after the iteration count and/or before the byte count to
 149 disambiguate them.  Any whitespace before or after the slash is ignored.
 150 .PP
 151 The format is required and must be surrounded by double quote (" ") marks.
 152 It is interpreted as a fprintf-style format string (see
 153 .BR fprintf (3),
 154 with the following exceptions:
 155 .TP
 156 1.
 157 An asterisk (*) may not be used as a field width or precision.
 158 .TP
 159 2.
 160 A byte count or field precision
 161 .I is
 162 required for each
 163 .B s
 164 conversion character (unlike the
 165 .BR fprintf (3)
 166 default which prints the entire string if the precision is unspecified).
 167 .TP
 168 3.
 169 The conversion characters
 170 .BR h , \ l , \ n , \ p ,
 171 .RB  and \ q
 172 are not supported.
 173 .TP
 174 4.
 175 The single character escape sequences described in the C standard are
 176 supported:
 177 .PP
 178 .RS 13
 179 .PD 0
 180 .TP 21
 181 NULL
 182 \e0
 183 .TP
 184 <alert character>
 185 \ea
 186 .TP
 187 <backspace>
 188 \eb
 189 .TP
 190 <form-feed>
 191 \ef
 192 .TP
 193 <newline>
 194 \en
 195 .TP
 196 <carriage return>
 197 \er
 198 .TP
 199 <tab>
 200 \et
 201 .TP
 202 <vertical tab>
 203 \ev
 204 .PD
 205 .RE
 206 .PP
 207 .SS Conversion strings
 208 The
 209 .B hexdump
 210 utility also supports the following additional conversion strings.
 211 .TP
 212 .B \&_a[dox]
 213 Display the input offset, cumulative across input files, of the next byte to
 214 be displayed.  The appended characters
 215 .BR d ,
 216 .BR o ,
 217 and
 218 .B x
 219 specify the display base as decimal, octal or hexadecimal respectively.
 220 .TP
 221 .B \&_A[dox]
 222 Identical to the
 223 .B \&_a
 224 conversion string except that it is only performed once, when all of the
 225 input data has been processed.
 226 .TP
 227 .B \&_c
 228 Output characters in the default character set.  Non-printing characters are
 229 displayed in three-character, zero-padded octal, except for those
 230 representable by standard escape notation (see above), which are displayed as
 231 two-character strings.
 232 .TP
 233 .B \&_p
 234 Output characters in the default character set.  Non-printing characters are
 235 displayed as a single
 236 .RB ' \&. '.
 237 .TP
 238 .B \&_u
 239 Output US ASCII characters, with the exception that control characters are
 240 displayed using the following, lower-case, names.  Characters greater than
 241 0xff, hexadecimal, are displayed as hexadecimal strings.
 242 .RS 10
 243 .TS
 244 tab(|);
 245 left l l l l l.
 246 000 nul|001 soh|002 stx|003 etx|004 eot|005 enq
 247 006 ack|007 bel|008 bs|009 ht|00A lf|00B vt
 248 00C ff|00D cr|00E so|00F si|010 dle|011 dc1
 249 012 dc2|013 dc3|014 dc4|015 nak|016 syn|017 etb
 250 018 can|019 em|01A sub|01B esc|01C fs|01D gs
 251 01E rs|01F us|0FF del
 252 .TE
 253 .SS Colors
 254 When put at the end of a format specifier, hexdump highlights the
 255 respective string with the color specified.  Conditions, if present, are
 256 evaluated prior to highlighting.
 257 .PP
 258 .B \&_L[color_unit_1,\:color_unit_2,\:...,\:color_unit_n]
 259 .PP
 260 The full syntax of a color unit is as follows:
 261 .PP
 262 .B [!]COLOR\:[:VALUE]\:[@OFFSET_START[-END]]
 263 .TP
 264 .B !
 265 Negate the condition.  Please note that it only makes sense to negate a
 266 unit if both a value/\:string and an offset are specified.  In that case
 267 the respective output string will be highlighted if and only if the
 268 value/\:string does not match the one at the offset.
 269 .TP
 270 .BR COLOR
 271 One of the 8 basic shell colors.
 272 .TP
 273 .B VALUE
 274 A value to be matched specified in hexadecimal, or octal base, or as a
 275 string.  Please note that the usual C escape sequences are not
 276 interpreted by hexdump inside the color_units.
 277 .TP
 278 .B OFFSET
 279 An offset or an offset range at which to check for a match.  Please note
 280 that lone OFFSET_START uses the same value as END offset.
 281 .SS Counters
 282 The default and supported byte counts for the conversion characters
 283 are as follows:
 284 .TP
 285 .BR \&%_c , \ \&%_p , \ \&%_u , \ \&%c
 286 One byte counts only.
 287 .TP
 288 .BR \&%d , \ \&%i , \ \&%o , \ \&%u , \ \&%X , \ \&%x
 289 Four byte default, one, two and four byte counts supported.
 290 .TP
 291 .BR \&%E , \ \&%e , \ \&%f , \ \&%G , \ \&%g
 292 Eight byte default, four byte counts supported.
 293 .PP
 294 The amount of data interpreted by each format string is the sum of the data
 295 required by each format unit, which is the iteration count times the byte
 296 count, or the iteration count times the number of bytes required by the
 297 format if the byte count is not specified.
 298 .PP
 299 The input is manipulated in
 300 .IR blocks ,
 301 where a block is defined as the largest amount of data specified by any
 302 format string.  Format strings interpreting less than an input block's worth
 303 of data, whose last format unit both interprets some number of bytes and does
 304 not have a specified iteration count, have the iteration count incremented
 305 until the entire input block has been processed or there is not enough data
 306 remaining in the block to satisfy the format string.
 307 .PP
 308 If, either as a result of user specification or
 309 .B hexdump
 310 modifying the iteration count as described above, an iteration count is
 311 greater than one, no trailing whitespace characters are output during the
 312 last iteration.
 313 .PP
 314 It is an error to specify a byte count as well as multiple conversion
 315 characters or strings unless all but one of the conversion characters or
 316 strings is
 317 .B \&_a
 318 or
 319 .BR \&_A .
 320 .PP
 321 If, as a result of the specification of the
 322 .B \-n
 323 option or end-of-file being reached, input data only partially satisfies a
 324 format string, the input block is zero-padded sufficiently to display all
 325 available data (i.e. any format units overlapping the end of data will
 326 display some number of the zero bytes).
 327 .PP
 328 Further output by such format strings is replaced by an equivalent number of
 329 spaces.  An equivalent number of spaces is defined as the number of spaces
 330 output by an
 331 .B s
 332 conversion character with the same field width and precision as the original
 333 conversion character or conversion string but with any
 334 .RB ' \&+ ',
 335 \' \',
 336 .RB ' \&# '
 337 conversion flag characters removed, and referencing a NULL string.
 338 .PP
 339 If no format strings are specified, the default display is very similar to
 340 the \fB\-x\fR output format (the \fB\-x\fR option causes more space to be
 341 used between format units than in the default output).
 342 .SH "EXIT STATUS"
 343 .B hexdump
 344 exits 0 on success and >0 if an error occurred.
 345 .SH EXAMPLES
 346 Display the input in perusal format:
 347 .nf
 348    "%06.6_ao "  12/1 "%3_u "
 349    "\et\et" "%_p "
 350    "\en"
 351 .nf
 352 .PP
 353 Implement the \-x option:
 354 .nf
 355    "%07.7_Ax\en"
 356    "%07.7_ax  " 8/2 "%04x " "\en"
 357 .nf
 358 .PP
 359 MBR Boot Signature example: Highlight the addresses cyan and the bytes at
 360 offsets 510 and 511 green if their value is 0xAA55, red otherwise.
 361 .nf
 362    "%07.7_Ax_L[cyan]\en"
 363    "%07.7_ax_L[cyan]  " 8/2 "   %04x_L[green:0xAA55@510-511,!red:0xAA55@510-511] " "\en"
 364 .nf
 365 .SH COLORS
 366 Implicit coloring can be disabled by an empty file \fI/etc/terminal-colors.d/hexdump.disable\fR.
 367
 368 See
 369 .BR terminal-colors.d (5)
 370 for more details about colorization configuration.
 371 .SH STANDARDS
 372 The
 373 .B hexdump
 374 utility is expected to be IEEE Std 1003.2 ("POSIX.2") compatible.
 375 .SH AVAILABILITY
 376 The hexdump command is part of the util-linux package and is available from
 377 .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 378 Linux Kernel Archive
 379 .UE .