PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

OD(1P)                    POSIX Programmer's Manual                   OD(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       od — dump files in various formats

SYNOPSIS         top

       od [−v] [−A address_base] [−j skip] [−N count] [−t type_string]...
           [file...]

       od [−bcdosx] [file] [[+]offset[.][b]]

DESCRIPTION         top

       The od utility shall write the contents of its input files to
       standard output in a user-specified format.

OPTIONS         top

       The od utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that
       the order of presentation of the −t options and the −bcdosx options
       is significant.

       The following options shall be supported:

       −A address_base
                 Specify the input offset base. See the EXTENDED DESCRIPTION
                 section.  The application shall ensure that the
                 address_base option-argument is a character. The characters
                 'd', 'o', and 'x' specify that the offset base shall be
                 written in decimal, octal, or hexadecimal, respectively.
                 The character 'n' specifies that the offset shall not be
                 written.

       −b        Interpret bytes in octal. This shall be equivalent to
                 −t o1.

       −c        Interpret bytes as characters specified by the current
                 setting of the LC_CTYPE category. Certain non-graphic
                 characters appear as C escapes: "NUL=\0", "BS=\b", "FF=\f",
                 "NL=\n", "CR=\r", "HT=\t"; others appear as 3-digit octal
                 numbers.

       −d        Interpret words (two-byte units) in unsigned decimal. This
                 shall be equivalent to −t u2.

       −j skip   Jump over skip bytes from the beginning of the input. The
                 od utility shall read or seek past the first skip bytes in
                 the concatenated input files. If the combined input is not
                 at least skip bytes long, the od utility shall write a
                 diagnostic message to standard error and exit with a non-
                 zero exit status.

                 By default, the skip option-argument shall be interpreted
                 as a decimal number. With a leading 0x or 0X, the offset
                 shall be interpreted as a hexadecimal number; otherwise,
                 with a leading '0', the offset shall be interpreted as an
                 octal number. Appending the character 'b', 'k', or 'm' to
                 offset shall cause it to be interpreted as a multiple of
                 512, 1024, or 1048576 bytes, respectively. If the skip
                 number is hexadecimal, any appended 'b' shall be considered
                 to be the final hexadecimal digit.

       −N count  Format no more than count bytes of input. By default, count
                 shall be interpreted as a decimal number. With a leading 0x
                 or 0X, count shall be interpreted as a hexadecimal number;
                 otherwise, with a leading '0', it shall be interpreted as
                 an octal number. If count bytes of input (after
                 successfully skipping, if −j skip is specified) are not
                 available, it shall not be considered an error; the od
                 utility shall format the input that is available.

       −o        Interpret words (two-byte units) in octal. This shall be
                 equivalent to −t o2.

       −s        Interpret words (two-byte units) in signed decimal. This
                 shall be equivalent to −t d2.

       −t type_string
                 Specify one or more output types. See the EXTENDED
                 DESCRIPTION section. The application shall ensure that the
                 type_string option-argument is a string specifying the
                 types to be used when writing the input data. The string
                 shall consist of the type specification characters a, c, d,
                 f, o, u, and x, specifying named character, character,
                 signed decimal, floating point, octal, unsigned decimal,
                 and hexadecimal, respectively. The type specification
                 characters d, f, o, u, and x can be followed by an optional
                 unsigned decimal integer that specifies the number of bytes
                 to be transformed by each instance of the output type. The
                 type specification character f can be followed by an
                 optional F, D, or L indicating that the conversion should
                 be applied to an item of type float, double, or long
                 double, respectively. The type specification characters d,
                 o, u, and x can be followed by an optional C, S, I, or L
                 indicating that the conversion should be applied to an item
                 of type char, short, int, or long, respectively. Multiple
                 types can be concatenated within the same type_string and
                 multiple −t options can be specified. Output lines shall be
                 written for each type specified in the order in which the
                 type specification characters are specified.

       −v        Write all input data. Without the −v option, any number of
                 groups of output lines, which would be identical to the
                 immediately preceding group of output lines (except for the
                 byte offsets), shall be replaced with a line containing
                 only an <asterisk> ('*').

       −x        Interpret words (two-byte units) in hexadecimal. This shall
                 be equivalent to −t x2.

       Multiple types can be specified by using multiple −bcdostx options.
       Output lines are written for each type specified in the order in
       which the types are specified.

OPERANDS         top

       The following operands shall be supported:

       file      A pathname of a file to be read. If no file operands are
                 specified, the standard input shall be used.

                 If there are no more than two operands, none of the −A, −j,
                 −N, −t, or −v options is specified, and either of the
                 following is true: the first character of the last operand
                 is a <plus-sign> ('+'), or there are two operands and the
                 first character of the last operand is numeric; the last
                 operand shall be interpreted as an offset operand on XSI-
                 conformant systems.  Under these conditions, the results
                 are unspecified on systems that are not XSI-conformant
                 systems.

       [+]offset[.][b]
                 The offset operand specifies the offset in the file where
                 dumping is to commence.  This operand is normally
                 interpreted as octal bytes. If '.'  is appended, the offset
                 shall be interpreted in decimal. If 'b' is appended, the
                 offset shall be interpreted in units of 512 bytes.

STDIN         top

       The standard input shall be used if no file operands are specified,
       and shall be used if a file operand is '−' and the implementation
       treats the '−' as meaning standard input.  Otherwise, the standard
       input shall not be used.  See the INPUT FILES section.

INPUT FILES         top

       The input files can be any file type.

ENVIRONMENT VARIABLES         top

       The following environment variables shall affect the execution of od:

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1‐2008, Section 8.2, Internationalization
                 Variables for the precedence of internationalization
                 variables used to determine the values of locale
                 categories.)

       LC_ALL    If set to a non-empty string value, override the values of
                 all the other internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of sequences of
                 bytes of text data as characters (for example, single-byte
                 as opposed to multi-byte characters in arguments and input
                 files).

       LC_MESSAGES
                 Determine the locale that should be used to affect the
                 format and contents of diagnostic messages written to
                 standard error.

       LC_NUMERIC
                 Determine the locale for selecting the radix character used
                 when writing floating-point formatted output.

       NLSPATH   Determine the location of message catalogs for the
                 processing of LC_MESSAGES.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       See the EXTENDED DESCRIPTION section.

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       The od utility shall copy sequentially each input file to standard
       output, transforming the input data according to the output types
       specified by the −t option or the −bcdosx options.  If no output type
       is specified, the default output shall be as if −t oS had been
       specified.

       The number of bytes transformed by the output type specifier c may be
       variable depending on the LC_CTYPE category.

       The default number of bytes transformed by output type specifiers d,
       f, o, u, and x corresponds to the various C-language types as
       follows. If the c99 compiler is present on the system, these
       specifiers shall correspond to the sizes used by default in that
       compiler. Otherwise, these sizes may vary among systems that conform
       to POSIX.1‐2008.

        *  For the type specifier characters d, o, u, and x, the default
           number of bytes shall correspond to the size of the underlying
           implementation's basic integer type. For these specifier
           characters, the implementation shall support values of the
           optional number of bytes to be converted corresponding to the
           number of bytes in the C-language types char, short, int, and
           long.  These numbers can also be specified by an application as
           the characters 'C', 'S', 'I', and 'L', respectively. The
           implementation shall also support the values 1, 2, 4, and 8, even
           if it provides no C-Language types of those sizes. The
           implementation shall support the decimal value corresponding to
           the C-language type long long.  The byte order used when
           interpreting numeric values is implementation-defined, but shall
           correspond to the order in which a constant of the corresponding
           type is stored in memory on the system.

        *  For the type specifier character f, the default number of bytes
           shall correspond to the number of bytes in the underlying
           implementation's basic double precision floating-point data type.
           The implementation shall support values of the optional number of
           bytes to be converted corresponding to the number of bytes in the
           C-language types float, double, and long double.  These numbers
           can also be specified by an application as the characters 'F',
           'D', and 'L', respectively.

       The type specifier character a specifies that bytes shall be
       interpreted as named characters from the International Reference
       Version (IRV) of the ISO/IEC 646:1991 standard. Only the least
       significant seven bits of each byte shall be used for this type
       specification. Bytes with the values listed in the following table
       shall be written using the corresponding names for those characters.

                           Table: Named Characters in od

         ┌─────────────┬──────────────┬───────────────────┬──────────────┐
         │Value   Name Value   Name Value     Name    Value   Name │
         ├─────────────┼──────────────┼───────────────────┼──────────────┤
         │\000    nul  │ \001    soh  │ \002    stx       │ \003    etx  │
         │\004    eot  │ \005    enq  │ \006    ack       │ \007    bel  │
         │\010    bs   │ \011    ht   │ \012    lf or nl* │ \013    vt   │
         │\014    ff   │ \015    cr   │ \016    so        │ \017    si   │
         │\020    dle  │ \021    dc1  │ \022    dc2       │ \023    dc3  │
         │\024    dc4  │ \025    nak  │ \026    syn       │ \027    etb  │
         │\030    can  │ \031    em   │ \032    sub       │ \033    esc  │
         │\034    fs   │ \035    gs   │ \036    rs        │ \037    us   │
         │\040    sp   │ \177    del  │                   │              │
         └─────────────┴──────────────┴───────────────────┴──────────────┘
       Note:     The "\012" value may be written either as lf or nl.

       The type specifier character c specifies that bytes shall be
       interpreted as characters specified by the current setting of the
       LC_CTYPE locale category. Characters listed in the table in the Base
       Definitions volume of POSIX.1‐2008, Chapter 5, File Format Notation
       ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v') shall be written as
       the corresponding escape sequences, except that <backslash> shall be
       written as a single <backslash> and a NUL shall be written as '\0'.
       Other non-printable characters shall be written as one three-digit
       octal number for each byte in the character. Printable multi-byte
       characters shall be written in the area corresponding to the first
       byte of the character; the two-character sequence "**" shall be
       written in the area corresponding to each remaining byte in the
       character, as an indication that the character is continued. When
       either the −j skip or −N count option is specified along with the c
       type specifier, and this results in an attempt to start or finish in
       the middle of a multi-byte character, the result is implementation-
       defined.

       The input data shall be manipulated in blocks, where a block is
       defined as a multiple of the least common multiple of the number of
       bytes transformed by the specified output types. If the least common
       multiple is greater than 16, the results are unspecified. Each input
       block shall be written as transformed by each output type, one per
       written line, in the order that the output types were specified. If
       the input block size is larger than the number of bytes transformed
       by the output type, the output type shall sequentially transform the
       parts of the input block, and the output from each of the
       transformations shall be separated by one or more <blank> characters.

       If, as a result of the specification of the −N option or end-of-file
       being reached on the last input file, input data only partially
       satisfies an output type, the input shall be extended sufficiently
       with null bytes to write the last byte of the input.

       Unless −A n is specified, the first output line produced for each
       input block shall be preceded by the input offset, cumulative across
       input files, of the next byte to be written. The format of the input
       offset is unspecified; however, it shall not contain any <blank>
       characters, shall start at the first character of the output line,
       and shall be followed by one or more <blank> characters. In addition,
       the offset of the byte following the last byte written shall be
       written after all the input data has been processed, but shall not be
       followed by any <blank> characters.

       If no −A option is specified, the input offset base is unspecified.

EXIT STATUS         top

       The following exit values shall be returned:

        0    All input files were processed successfully.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       XSI-conformant applications are warned not to use filenames starting
       with '+' or a first operand starting with a numeric character so that
       the old functionality can be maintained by implementations, unless
       they specify one of the −A, −j, or −N options. To guarantee that one
       of these filenames is always interpreted as a filename, an
       application could always specify the address base format with the −A
       option.

EXAMPLES         top

       If a file containing 128 bytes with decimal values zero to 127, in
       increasing order, is supplied as standard input to the command:

           od −A d −t a

       on an implementation using an input block size of 16 bytes, the
       standard output, independent of the current locale setting, would be
       similar to:

           0000000 nul soh stx etx eot enq ack bel  bs  ht  nl  vt  ff  cr  so  si
           0000016 dle dc1 dc2 dc3 dc4 nak syn etb can  em sub esc  fs  gs  rs  us
           0000032  sp   !   "   #   $   %   &   '   (   )   *   +   ,   −   .  /
           0000048   0   1   2   3   4   5   6   7   8   9   :   ;   <   =   >   ?
           0000064   @   A   B   C   D   E   F   G   H   I   J   K   L   M   N   O
           0000080   P   Q   R   S   T   U   V   W   X   Y   Z   [   \   ]   ^   _
           0000096   `   a   b   c   d   e   f   g   h   i   j   k   l   m   n   o
           0000112   p   q   r   s   t   u   v   w   x   y   z   {   |   }   ~ del
           0000128

       Note that this volume of POSIX.1‐2008 allows nl or lf to be used as
       the name for the ISO/IEC 646:1991 standard IRV character with decimal
       value 10. The IRV names this character lf (line feed), but
       traditional implementations have referred to this character as
       newline (nl) and the POSIX locale character set symbolic name for the
       corresponding character is a <newline>.

       The command:

           od −A o −t o2x2x −N 18

       on a system with 32-bit words and an implementation using an input
       block size of 16 bytes could write 18 bytes in approximately the
       following format:

           0000000 032056 031440 041123 042040 052516 044530 020043 031464
                     342e   3320   4253   4420   554e   4958   2023   3334
                        342e3320      42534420      554e4958      20233334
           0000020 032472
                     353a
                        353a0000
           0000022

       The command:

           od −A d −t f −t o4 −t x4 −N 24 −j 0x15

       on a system with 64-bit doubles (for example, IEEE Std 754‐1985
       double precision floating-point format) would skip 21 bytes of input
       data and then write 24 bytes in approximately the following format:

           0000000    1.00000000000000e+00    1.57350000000000e+01
                   07774000000 00000000000 10013674121 35341217270
                      3ff00000    00000000    402f3851    eb851eb8
           0000016    1.40668230000000e+02
                   10030312542 04370303230
                      40619562    23e18698
           0000024

RATIONALE         top

       The od utility went through several names in early proposals,
       including hd, xd, and most recently hexdump.  There were several
       objections to all of these based on the following reasons:

        *  The hd and xd names conflicted with historical utilities that
           behaved differently.

        *  The hexdump description was much more complex than needed for a
           simple dump utility.

        *  The od utility has been available on all historical
           implementations and there was no need to create a new name for a
           utility so similar to the historical od utility.

       The original reasons for not standardizing historical od were also
       fairly widespread. Those reasons are given below along with rationale
       explaining why the standard developers believe that this version does
       not suffer from the indicated problem:

        *  The BSD and System V versions of od have diverged, and the
           intersection of features provided by both does not meet the needs
           of the user community. In fact, the System V version only
           provides a mechanism for dumping octal bytes and shorts, signed
           and unsigned decimal shorts, hexadecimal shorts, and ASCII
           characters. BSD added the ability to dump floats, doubles, named
           ASCII characters, and octal, signed decimal, unsigned decimal,
           and hexadecimal longs.  The version presented here provides more
           normalized forms for dumping bytes, shorts, ints, and longs in
           octal, signed decimal, unsigned decimal, and hexadecimal; float,
           double, and long double; and named ASCII as well as current
           locale characters.

        *  It would not be possible to come up with a compatible superset of
           the BSD and System V flags that met the requirements of the
           standard developers. The historical default od output is the
           specified default output of this utility. None of the option
           letters chosen for this version of od conflict with any of the
           options to historical versions of od.

        *  On systems with different sizes for short, int, and long, there
           was no way to ask for dumps of ints, even in the BSD version.
           Because of the way options are named, the name space could not be
           extended to solve these problems. This is why the −t option was
           added (with type specifiers more closely matched to the printf()
           formats used in the rest of this volume of POSIX.1‐2008) and the
           optional field sizes were added to the d, f, o, u, and x type
           specifiers. It is also one of the reasons why the historical
           practice was not mandated as a required obsolescent form of od.
           (Although the old versions of od are not listed as an obsolescent
           form, implementations are urged to continue to recognize the
           older forms for several more years.) The a, c, f, o, and x types
           match the meaning of the corresponding format characters in the
           historical implementations of od except for the default sizes of
           the fields converted. The d format is signed in this volume of
           POSIX.1‐2008 to match the printf() notation. (Historical versions
           of od used d as a synonym for u in this version. The System V
           implementation uses s for signed decimal; BSD uses i for signed
           decimal and s for null-terminated strings.) Other than d and u,
           all of the type specifiers match format characters in the
           historical BSD version of od.

           The sizes of the C-language types char, short, int, long, float,
           double, and long double are used even though it is recognized
           that there may be zero or more than one compiler for the C
           language on an implementation and that they may use different
           sizes for some of these types. (For example, one compiler might
           use 2 bytes shorts, 2 bytes ints, and 4 bytes longs, while
           another compiler (or an option to the same compiler) uses 2 bytes
           shorts, 4 bytes ints, and 4 bytes longs.)  Nonetheless, there has
           to be a basic size known by the implementation for these types,
           corresponding to the values reported by invocations of the
           getconf utility when called with system_var operands {UCHAR_MAX},
           {USHORT_MAX}, {UINT_MAX}, and {ULONG_MAX} for the types char,
           short, int, and long, respectively. There are similar constants
           required by the ISO C standard, but not required by the System
           Interfaces volume of POSIX.1‐2008 or this volume of POSIX.1‐2008.
           They are {FLT_MANT_DIG}, {DBL_MANT_DIG}, and {LDBL_MANT_DIG} for
           the types float, double, and long double, respectively. If the
           optional c99 utility is provided by the implementation and used
           as specified by this volume of POSIX.1‐2008, these are the sizes
           that would be provided. If an option is used that specifies
           different sizes for these types, there is no guarantee that the
           od utility is able to interpret binary data output by such a
           program correctly.

           This volume of POSIX.1‐2008 requires that the numeric values of
           these lengths be recognized by the od utility and that symbolic
           forms also be recognized. Thus, a conforming application can
           always look at an array of unsigned long data elements using od
           −t uL.

        *  The method of specifying the format for the address field based
           on specifying a starting offset in a file unnecessarily tied the
           two together. The −A option now specifies the address base and
           the −S option specifies a starting offset.

        *  It would be difficult to break the dependence on US ASCII to
           achieve an internationalized utility. It does not seem to be any
           harder for od to dump characters in the current locale than it is
           for the ed or sed l commands. The c type specifier does this
           without difficulty and is completely compatible with the
           historical implementations of the c format character when the
           current locale uses a superset of the ISO/IEC 646:1991 standard
           as a codeset. The a type specifier (from the BSD a format
           character) was left as a portable means to dump ASCII (or more
           correctly ISO/IEC 646:1991 standard (IRV)) so that headers
           produced by pax could be deciphered even on systems that do not
           use the ISO/IEC 646:1991 standard as a subset of their base
           codeset.

       The use of "**" as an indication of continuation of a multi-byte
       character in c specifier output was chosen based on seeing an
       implementation that uses this method. The continuation bytes have to
       be marked in a way that is not ambiguous with another single-byte or
       multi-byte character.

       An early proposal used −S and −n, respectively, for the −j and −N
       options eventually selected. These were changed to avoid conflicts
       with historical implementations.

       The original standard specified −t o2 as the default when no output
       type was given. This was changed to −t oS (the length of a short) to
       accommodate a supercomputer implementation that historically used 64
       bits as its default (and that defined shorts as 64 bits). This change
       should not affect conforming applications. The requirement to support
       lengths of 1, 2, and 4 was added at the same time to address an
       historical implementation that had no two-byte data types in its C
       compiler.

       The use of a basic integer data type is intended to allow the
       implementation to choose a word size commonly used by applications on
       that architecture.

       Earlier versions of this standard allowed for implementations with
       bytes other than eight bits, but this has been modified in this
       version.

FUTURE DIRECTIONS         top

       All option and operand interfaces marked XSI may be removed in a
       future version.

SEE ALSO         top

       c99(1p), sed(1p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 5, File Format
       Notation, Chapter 8, Environment Variables, Section 12.2, Utility
       Syntax Guidelines

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                              OD(1P)