hd(1)

hd -- display files in a specified format

Synopsis

   hd [-[abwl][xdo][cAS][t]] [-s offset] [-n count] [file]

Description

The hd command displays the contents of files in hexadecimal octal, decimal, and character formats. Control over the specification of ranges of characters is also available. The default behavior is with the following specifiers set: -abA. This says that addresses (file offsets) and bytes are printed in hexadecimal and that only ASCII characters are also printed. If no file argument is given, the standard input is read.

Command options

Format specifiers, described below, may specify addresses, bytes, words (2 bytes), or longs (4 bytes). Output specifiers determine whether to print only the ASCII-readable characters, or to print all printable characters, special C escapes as defined in the language, and remaining values in the specified base. Base specifiers determine whether the data is to be printed in hexadecimal, decimal, or octal. A special flag directs output to a test file, with each line preceded by the address in the file.

Format and base specifiers may be freely combined and repeated as desired in order to specify different bases (hexadecimal, decimal, and/or octal) for different formats (addresses, bytes, and so on). All format specifiers appearing in a single argument are applied as appropriate to all other flags in that argument.

If no format specifier is given, -abwlc is used as the default. If no other output format (other than addresses, a) is given, bx is assumed (byte, in hexadecimal).

Format specifiers are used as follows:

-abwl

Format type specifier for address, bytes, words, and longs, respectively. Only one base specifier (described below) is used for addresses; the address appears on the first line of output that begins each new offset in the input.

cAS

These are the output specifiers, and should be entered directly to the right of one or more of the format type specifiers (that is, a, b, w, or l). If only one output specifier appears on the command line, it is assumed to apply to all the format type specifiers.

The character format flag, c, directs hd to print printable characters unchanged, special C escapes as defined in the language, and remaining values in the specified base.

The format flag A directs hd to print all printable characters unchanged, and all others as a period (.).

The format flag S directs hd to print all 7 bit printable ASCII characters unchanged, and all others as a period (.).

xdo

The base specifiers denote hexadecimal, decimal and octal. If no base specifier is given, the default is xdo, meaning present the output in all three formats, hexadecimal, decimal, and octal.

t

Print a test file, each line preceded by the address in the file. Normally, lines should be terminated by a \n character; but long lines will be broken up. Control characters in the range 0x00 to 0x1f are printed as `^@' to `^_'. Bytes with the high bit set are preceded by a tilde (~) and printed as if the high bit were not set. The special characters (^,~,\) are preceded by a backslash (\) to escape their special meaning. As special cases, two values are represented numerically as `\177' and `\377'. This flag will override all output format specifiers except addresses.

Following are the remaining options for hd:

-s offset

Specify the beginning offset in the file where printing is to begin. If no `file' argument is given, or if a seek fails because the input is a pipe, `offset' bytes are read from the input and discarded. Otherwise, a seek error will terminate processing of the current file.

The offset may be given in decimal, hexadecimal (preceded by `Ox'), or octal (preceded by a `0'). It is optionally followed by one of the following multipliers: w, l, b, or k; for words (2 bytes), long words (4 bytes), blocks (512 bytes), or K bytes (1024 bytes). Note that this is the one case where "b" does not stand for bytes. Since specifying a hexadecimal offset in blocks would result in an ambiguous trailing `b', any offset and multiplier may be separated by an asterisk (*).

-n count

Specify the number of bytes to process. The count is in the same format as offset, above.