od is a
command
Command may refer to:
Computing
* Command (computing), a statement in a computer language
* command (Unix), a Unix command
* COMMAND.COM, the default operating system shell and command-line interpreter for DOS
* Command key, a modifier key on A ...
on various
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
s for displaying ("dumping") data in various
human-readable
In computing, a human-readable medium or human-readable format is any encoding of data or information that can be naturally read by humans, resulting in human-readable data. It is often encoded as ASCII or Unicode text, rather than as binary da ...
output formats. The name is an acronym for "
octal
Octal (base 8) is a numeral system with eight as the base.
In the decimal system, each place is a power of ten. For example:
: \mathbf_ = \mathbf \times 10^1 + \mathbf \times 10^0
In the octal system, each place is a power of eight. For ex ...
dump" since it defaults to printing in the
octal
Octal (base 8) is a numeral system with eight as the base.
In the decimal system, each place is a power of ten. For example:
: \mathbf_ = \mathbf \times 10^1 + \mathbf \times 10^0
In the octal system, each place is a power of eight. For ex ...
data format.
Overview
The
od program can display output in a variety of formats, including
octal
Octal (base 8) is a numeral system with eight as the base.
In the decimal system, each place is a power of ten. For example:
: \mathbf_ = \mathbf \times 10^1 + \mathbf \times 10^0
In the octal system, each place is a power of eight. For ex ...
,
hexadecimal
Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo ...
,
decimal
The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers (''decimal fractions'') of th ...
, and
ASCII
ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...
. It is useful for visualizing data that is not in a human-readable format, like the
executable
In computer science, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instruction (computer science), in ...
code of a program, or where the primary form is ambiguous (e.g. some Latin, Greek and Cyrillic characters looking similar).
od is one of the earliest
Unix
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
programs, having appeared in version 1
AT&T Unix
Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...
. It is also specified in the
POSIX
The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with comm ...
standards. The implementation for
od used on
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
systems is usually provided by
GNU Core Utilities
The GNU Core Utilities or coreutils is a collection of GNU software that implements many standard, Unix-based shell commands. The utilities generally provide POSIX compliant interface when the environment variable is set, but otherwise offers ...
.
Since it predates the
Bourne shell
The Bourne shell (sh) is a shell command-line interpreter for computer operating systems. It first appeared on Version 7 Unix, as its default shell. Unix-like systems continue to have /bin/sh—which will be the Bourne shell, or a symbolic lin ...
, its existence causes an inconsistency in the
do loop syntax. Other loops and logical blocks are opened by the name, and closed by the reversed name, e.g.
if ... fi and
case ... esac, but
od's existence necessitates
do ... done.
The command is available as a separate package for
Microsoft Windows
Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
as part of the
UnxUtils
UnxUtils is a collection of utility programs that provide popular Unix-based shell commands ported from GNU implementations as native Windows programs that depend only on Win32 and the Microsoft C- runtime ( msvcrt.dll). The collection wa ...
collection of
native
Native may refer to:
People
* '' Jus sanguinis'', nationality by blood
* '' Jus soli'', nationality by location of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Nat ...
Win32
The Windows API, informally WinAPI, is the foundational application programming interface (API) that allows a computer program to access the features of the Microsoft Windows operating system in which the program is running. Programs can acces ...
ports Ports collections (or ports trees, or just ports) are the sets of makefiles and Patch (Unix), patches provided by the BSD-based operating systems, FreeBSD, NetBSD, and OpenBSD, as a simple method of installing software or creating binary packages. T ...
of common GNU Unix-like utilities. The command has also been ported to the
IBM i
IBM i (the ''i'' standing for ''integrated'') is an operating system developed by IBM for IBM Power Systems. It was originally released in 1988 as OS/400, as the sole operating system of the IBM AS/400 line of systems. It was renamed to i5/OS in 2 ...
operating system.
Example session
Normally a dump of an executable file is very long. The
head
A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...
program prints out the first few lines of the output. Here is an example of a dump of the
"Hello world" program,
piped through head.
% od hello , head
0000000 042577 043114 000401 000001 000000 000000 000000 000000
0000020 000002 000003 000001 000000 101400 004004 000064 000000
0000040 003610 000000 000000 000000 000064 000040 000006 000050
0000060 000033 000030 000006 000000 000064 000000 100064 004004
0000100 100064 004004 000300 000000 000300 000000 000005 000000
0000120 000004 000000 000003 000000 000364 000000 100364 004004
0000140 100364 004004 000023 000000 000023 000000 000004 000000
0000160 000001 000000 000001 000000 000000 000000 100000 004004
0000200 100000 004004 002121 000000 002121 000000 000005 000000
0000220 010000 000000 000001 000000 002124 000000 112124 004004
Here is an example of
od used to diagnose the output of
echo
In audio signal processing and acoustics, an echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the lis ...
where the user types and after writing "Hello" to literal insert a
tab and
^C character:
% echo "Hello ^C" , od -cb
0000000 H e l l o \t 003 \n
110 145 154 154 157 011 003 012
0000010
can be used to fetch random numbers from the cryptographic-quality random number generator
/dev/urandom. For example:
See also
*
Hex editor
A hex editor (or ''binary file editor'' or ''byte editor'') is a computer program that allows for manipulation of the fundamental Binary file, binary data that constitutes a computer file. The name 'hex' comes from 'hexadecimal', a standard numer ...
*
Hex dump
In computing, a hex dump is a textual hexadecimal view (on screen or paper) of computer data, from memory or from a computer file or storage device. Use of a hex dump of data is usually done in the context of either debugging, reverse engineer ...
References
External links
*
od - GNU Core Utilities manpage
{{Core Utilities commands
Unix SUS2008 utilities
IBM i Qshell commands