hd

Display files in decimal, hex, octal, or ASCII (UNIX)

Syntax:

hd [-8] [-A format] [-n count] [-s skip] 
   [-t format[fmt_string]] [-v] [file...]

Options:

-8

Use 8-bit ASCII characters (default 7).

-A format

Display the file offset field in the specified format. Valid formats are:

• d -- decimal, 9 digits
• n -- none (omit this field)
• o -- octal, 10 digits
• x -- hexadecimal, 7 digits.

-n count

Display only count bytes of input. You can add a trailing character to specify units of blocks (b), kilobytes (k), or megabytes (m).

-s skip

Ignore the first skip bytes of data. You can add a trailing character to specify units of blocks (b), kilobytes (k), or megabytes (m).

-t format[fmt_string]

Use this output/display format; see "Output formats," below.

The default format is x1.

-v

Be verbose. If you don't specify the -v option, hd folds multiple identical lines into a single line that contains an asterisk (*).

file

The pathname of an input file. If you don't specify any files, hd reads from standard input. If a file is a hyphen (-), hd reads from the standard input at that point in the sequence.

Description:

The hd utility displays data in decimal, hex, octal, or ASCII. The name "hd" (hex dump) is derived from the default output format.

The hd utility processes input in 16-byte units that are formatted into a line. In the default output format:

• the file offset field is displayed in hex, 7 digits
• a space separates the file offset field from the data
• the data is displayed as 16 space-separated bytes in hex
• the same data is also displayed in ASCII, if printable; unprintable data appears as dots.

For example:

$ echo "abcdefghijklmnopqrstuvwxyz01234" | hd
0000000: 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 abcdefghijklmnop
0000010: 71 72 73 74 75 76 77 78 79 7a 30 31 32 33 34 0a qrstuvwxyz01234.

To exclude part of the input, use the -n and -s options. You can specify the arguments to these options in hex (using a 0x prefix) or octal (using a 0 prefix). The default units for these options are bytes, but you can specify different units as follows:

Output formats

To specify the output format, use the -t option. The format argument -- which you can specify in decimal, hex, or octal -- tells hd which format to use for presenting the output:

a

Named characters. Display printable characters as themselves, and nonprintable characters as a single dot (.).

c

Characters. Display printable characters as themselves; display all other characters as 2-digit hex values, except for the following:

ASCII mnemonic	Value	Representation
NUL	00	\0
<alert>	07	\a
<backspace>	08	\b
<tab>	09	\t
<newline>	0a	\n
<vertical tab>	0b	\v
<formfeed>	0c	\f
<carriage return>	0d	\r

d[1|2|4|C|S|I|L]

Decimal, in objects the size of an int by default.

f[4|8|F|D|L]

Floating point, in objects the size of an float by default.

o[1|2|4|C|S|I|L]

Octal, in objects the size of an int by default.

u[1|2|4|C|S|I|L]

Unsigned decimal, in objects the size of an int by default.

x[1|2|4|C|S|I|L]

Hexadecimal, in objects the size of an int by default.

The input, processed in 16-byte units formatted into a line, is displayed according to the size you choose:

Examples:

Display the second to eleventh sectors of the hard disk, /dev/hd0:

hd -s 1b -n 10b /dev/hd0

Exit status:

0

All input files were processed successfully.

>0

An error occurred.

See also:

od