HEXDUMP(1)                 OpenBSD Reference Manual                 HEXDUMP(1)

NAME
     hexdump - ascii, decimal, hexadecimal, octal dump



SYNOPSIS
     hexdump [-bcdovx] [-e format_string] [-f format_file] [-n length]
             [-s offset] file [...]

DESCRIPTION
     The hexdump utility is a filter which displays the specified files, or
     the standard input, if no files are specified, in a user-specified for-
     mat.

     The options are as follows:

     -b          One-byte octal display. Display the input offset in hexadeci-
                 mal, followed by sixteen space-separated, three column, zero-
                 filled, bytes of input data, in octal, per line.

     -c          One-byte character display. Display the input offset in hex-
                 adecimal, followed by sixteen space-separated, three column,
                 space-filled, characters of input data per line.

     -d          Two-byte decimal display. Display the input offset in hex-
                 adecimal, followed by eight space-separated, five column, ze-
                 ro-filled, two-byte units of input data, in unsigned decimal,
                 per line.

     -e format_string
                 Specify a format string to be used for displaying data.

     -f format_file
                 Specify a file that contains one or more newline separated
                 format strings.  Empty lines and lines whose first non-blank
                 character is a hash mark (``#'') are ignored.

     -n length   Interpret only length bytes of input.

     -o          Two-byte octal display. Display the input offset in hexadeci-
                 mal, followed by eight space-separated, six column, zero-
                 filled, two byte quantities of input data, in octal, per
                 line.

     -s offset   Skip offset bytes from the beginning of the input.  By de-
                 fault, offset is interpreted as a decimal number.  With a
                 leading 0x or 0X, offset is interpreted as a hexadecimal num-
                 ber, otherwise, with a leading 0, offset is interpreted as an
                 octal number.  Appending the character b, k, or m to offset
                 causes it to be interpreted as a multiple of 512, 1024, or
                 1048576, respectively.

     -v          The -v option causes hexdump to display all input data.
                 Without the -v option, any number of groups of output lines,
                 which would be identical to the immediately preceding group
                 of output lines (except for the input offsets), are replaced
                 with a line comprised of a single asterisk.

     -x          Two-byte hexadecimal display. Display the input offset in
                 hexadecimal, followed by eight, space separated, four column,
                 zero-filled, two-byte quantities of input data, in hexadeci-
                 mal, per line.

     For each input file, hexdump sequentially copies the input to standard
     output, transforming the data according to the format strings specified
     by the -e and -f options, in the order that they were specified.

   Formats
     A format string contains any number of format units, separated by whites-
     pace.  A format unit contains up to three items: an iteration count, a
     byte count, and a format.

     The iteration count is an optional positive integer, which defaults to
     one.  Each format is applied iteration count times.

     The byte count is an optional positive integer.  If specified it defines
     the number of bytes to be interpreted by each iteration of the format.

     If an iteration count and/or a byte count is specified, a single slash
     must be placed after the iteration count and/or before the byte count to
     disambiguate them.  Any whitespace before or after the slash is ignored.

     The format is required and must be surrounded by double quote (" ")
     marks.  It is interpreted as an fprintf-style format string (see
     fprintf(3)),  with the following exceptions:

           -   An asterisk (*) may not be used as a field width or precision.

           -   A byte count or field precision is required for each ``s'' con-
               version character (unlike the fprintf(3) default which prints
               the entire string if the precision is unspecified).

           -   The conversion characters ``h'', ``n'', and ``p'' are not sup-
               ported.

           -   The single character escape sequences described in the C stan-
               dard are supported:

                     NUL                  \0
                     <alert character>    \a
                     <backspace>          \b
                     <form-feed>          \f
                     <newline>            \n
                     <carriage return>    \r
                     <tab>                \t
                     <vertical tab>       \v

     hexdump also supports the following additional conversion strings:

     _a[dox]     Display the input offset, cumulative across input files, of
                 the next byte to be displayed.  The appended characters d, o,
                 and x specify the display base as decimal, octal or hexadeci-
                 mal respectively.

     _A[dox]     Identical to the _a conversion string except that it is only
                 performed once, when all of the input data has been pro-
                 cessed.

     _c          Output characters in the default character set.  Nonprinting
                 characters are displayed in three character, zero-padded oc-
                 tal, except for those representable by standard escape nota-
                 tion (see above), which are displayed as two character
                 strings.

     _p          Output characters in the default character set.  Nonprinting
                 characters are displayed as a single ``.''.

     _u          Output US ASCII characters, with the exception that control
                 characters are displayed using the following, lower-case,
                 names.  Characters greater than 0xff, hexadecimal, are dis-
                 played as hexadecimal strings.

                 000 nul  001 soh  002 stx  003 etx  004 eot  005 enq
                 006 ack  007 bel  008 bs   009 ht   00A lf   00B vt
                 00C ff   00D cr   00E so   00F si   010 dle  011 dc1
                 012 dc2  013 dc3  014 dc4  015 nak  016 syn  017 etb
                 018 can  019 em   01A sub  01B esc  01C fs   01D gs
                 01E rs   01F us   0FF del

     The default and supported byte counts for the conversion characters are
     as follows:

           %_c, %_p, %_u, %c       One byte counts only.

           %d, %i, %o, %u, %X, %x  Four byte default, one and two byte counts
                                   supported.

           %E, %e, %f, %G, %g      Eight byte default, four byte counts sup-
                                   ported.

     The amount of data interpreted by each format string is the sum of the
     data required by each format unit, which is the iteration count times the
     byte count, or the iteration count times the number of bytes required by
     the format if the byte count is not specified.

     The input is manipulated in ``blocks'', where a block is defined as the
     largest amount of data specified by any format string.  Format strings
     interpreting less than an input block's worth of data, whose last format
     unit both interprets some number of bytes and does not have a specified
     iteration count, have the iteration count incremented until the entire
     input block has been processed or there is not enough data remaining in
     the block to satisfy the format string.

     If, either as a result of user specification or hexdump modifying the it-
     eration count as described above, an iteration count is greater than one,
     no trailing whitespace characters are output during the last iteration.

     It is an error to specify a byte count as well as multiple conversion
     characters or strings unless all but one of the conversion characters or
     strings is _a or _A.

     If, as a result of the specification of the -n option or end-of-file be-
     ing reached, input data only partially satisfies a format string, the in-
     put block is zero-padded sufficiently to display all available data (i.e.
     any format units overlapping the end of data will display some number of
     the zero bytes).

     Further output by such format strings is replaced by an equivalent number
     of spaces.  An equivalent number of spaces is defined as the number of
     spaces output by an s conversion character with the same field width and
     precision as the original conversion character or conversion string but
     with any ``+'', `` '', ``#'' conversion flag characters removed, and ref-
     erencing a NULL string.

     If no format strings are specified, the default display is equivalent to
     specifying the -x option.

     hexdump exits 0 on success or >0 if an error occurred.

EXAMPLES
     Display the input in perusal format:

           "%06.6_ao "  12/1 "%3_u "
           "\t\t" "%_p "
           "\n"

     Implement the -x option:

           "%07.7_Ax\n"
           "%07.7_ax  " 8/2 "%04x " "\n"

STANDARDS
     The hexdump utility is expected to be IEEE Std1003.2 (``POSIX.2'') com-
     patible.

OpenBSD 2.6                      July 27, 1991                               4