od is a

command Command may refer to: Computing * Command (computing), a statement in a computer language * COMMAND.COM, the default operating system shell and command-line interpreter for DOS * Command key, a modifier key on Apple Macintosh computer keyboards ...

on various

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

s for displaying ("dumping") data in various human-readable output formats. The name is an acronym for "

octal The octal numeral system, or oct for short, is the radix, base-8 number system, and uses the Numerical digit, digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, ...

dump" since it defaults to printing in the

data format.

Overview

The od program can display output in a variety of formats, including

hexadecimal In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, h ...

, decimal, and

ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...

. It is useful for visualizing data that is not in a human-readable format, like the

executable In computing, 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 instructions", as opposed to a data fil ...

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, multiuser 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. 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 both the system- and user-level application programming inte ...

standards. The implementation for od used on

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...

systems is usually provided by GNU Core Utilities. Since it predates the

Bourne shell The Bourne shell (sh) is a shell command-line interpreter for computer operating systems. The Bourne shell was the default shell for Version 7 Unix. Unix-like systems continue to have /bin/sh—which will be the Bourne shell, or a symbolic link ...

, 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 as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. The command has also been ported to the IBM i 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 animals may no ...

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 li ...

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

References

External links

*
od - GNU Core Utilities manpage
{{Core Utilities commands Unix SUS2008 utilities IBM i Qshell commands

Overview

Example session

See also

References

External links