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 and options, in the order that they were specified.
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 (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'' conversion character (unlike the fprintf (3) default which prints the entire string if the precision is unspecified). The conversion characters ``h'', ``l'', ``n'', ``p'' and ``q'' are not supported. The single character escape sequences described in the C standard 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 the following additional conversion strings:
The default and supported byte counts for the conversion characters are as follows:
Li %_c , %_p , %_u , %c One byte counts only. Xo
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 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 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 referencing a NULL string.
If no format strings are specified, the default display is equivalent to specifying the option.
hexdump exits 0 on success and >0 if an error occurred.
Implement the -x option:
"%07.7_Ax\n" "%07.7_ax " 8/2 "%04x " "\n"