RTEMS Shell User's Guide
hexdump [-bcCdovx] [-e format_string] [-f format_file] [-n length] [-s skip] file ...
The hexdump utility is a filter which displays the specified files, or the standard input, if no files are specified, in a user specified format.
The options are as follows:
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.
A format string contains any number of format units, separated by whitespace. 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 a fprintf-style format string (see fprintf), with the following exceptions:
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:
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 07F 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, two, four and eight byte counts supported. %E, %e, %f, %G, %g Eight byte default, four byte counts supported.
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 iteration 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 being reached, input data only partially satisfies a format string, the input block is zero-padded sufficiently to display all available data (i.e. any format units overlapping the end of data will display some num- ber 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.
This command returns 0 on success and non-zero if an error is encountered.
The following is an example of how to use
SHLL [/] $ hexdump -C -n 512 /dev/hda1
This command is included in the default shell command set. When
building a custom command set, define
CONFIGURE_SHELL_COMMAND_HEXDUMP to have this command included.
This command can be excluded from the shell command set by defining
CONFIGURE_SHELL_NO_COMMAND_HEXDUMP when all shell commands have
hexdump command is implemented by a C language function
which has the following prototype:
int rtems_shell_rtems_main_hexdump( int argc, char **argv );
The configuration structure for the
hexdump has the following
extern rtems_shell_cmd_t rtems_shell_HEXDUMP_Command;
RTEMS Shell User's Guide
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