1OD(1P) POSIX Programmer's Manual OD(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 od — dump files in various formats
14
16 od [−v] [−A address_base] [−j skip] [−N count] [−t type_string]...
17 [file...]
18 od [−bcdosx] [file] [[+]offset[.][b]]
20
22 The od utility shall write the contents of its input files to standard
23 output in a user-specified format.
24
26 The od utility shall conform to the Base Definitions volume of
27 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that the
28 order of presentation of the −t options and the −bcdosx options is sig‐
29 nificant.
30 The following options shall be supported:
32 −A address_base
34 Specify the input offset base. See the EXTENDED DESCRIPTION
35 section. The application shall ensure that the address_base
36 option-argument is a character. The characters 'd', 'o', and
37 'x' specify that the offset base shall be written in decimal,
38 octal, or hexadecimal, respectively. The character 'n' speci‐
39 fies that the offset shall not be written.
40 −b Interpret bytes in octal. This shall be equivalent to −t o1.
42 −c Interpret bytes as characters specified by the current set‐
44 ting of the LC_CTYPE category. Certain non-graphic characters
45 appear as C escapes: "NUL=\0", "BS=\b", "FF=\f", "NL=\n",
46 "CR=\r", "HT=\t"; others appear as 3-digit octal numbers.
47 −d Interpret words (two-byte units) in unsigned decimal. This
49 shall be equivalent to −t u2.
50 −j skip Jump over skip bytes from the beginning of the input. The od
52 utility shall read or seek past the first skip bytes in the
53 concatenated input files. If the combined input is not at
54 least skip bytes long, the od utility shall write a diagnos‐
55 tic message to standard error and exit with a non-zero exit
56 status.
57 By default, the skip option-argument shall be interpreted as
59 a decimal number. With a leading 0x or 0X, the offset shall
60 be interpreted as a hexadecimal number; otherwise, with a
61 leading '0', the offset shall be interpreted as an octal num‐
62 ber. Appending the character 'b', 'k', or 'm' to offset shall
63 cause it to be interpreted as a multiple of 512, 1024, or
64 1048576 bytes, respectively. If the skip number is hexadeci‐
65 mal, any appended 'b' shall be considered to be the final
66 hexadecimal digit.
67 −N count Format no more than count bytes of input. By default, count
69 shall be interpreted as a decimal number. With a leading 0x
70 or 0X, count shall be interpreted as a hexadecimal number;
71 otherwise, with a leading '0', it shall be interpreted as an
72 octal number. If count bytes of input (after successfully
73 skipping, if −j skip is specified) are not available, it
74 shall not be considered an error; the od utility shall format
75 the input that is available.
76 −o Interpret words (two-byte units) in octal. This shall be
78 equivalent to −t o2.
79 −s Interpret words (two-byte units) in signed decimal. This
81 shall be equivalent to −t d2.
82 −t type_string
84 Specify one or more output types. See the EXTENDED DESCRIP‐
85 TION section. The application shall ensure that the
86 type_string option-argument is a string specifying the types
87 to be used when writing the input data. The string shall con‐
88 sist of the type specification characters a, c, d, f, o, u,
89 and x, specifying named character, character, signed decimal,
90 floating point, octal, unsigned decimal, and hexadecimal,
91 respectively. The type specification characters d, f, o, u,
92 and x can be followed by an optional unsigned decimal integer
93 that specifies the number of bytes to be transformed by each
94 instance of the output type. The type specification character
95 f can be followed by an optional F, D, or L indicating that
96 the conversion should be applied to an item of type float,
97 double, or long double, respectively. The type specification
98 characters d, o, u, and x can be followed by an optional C,
99 S, I, or L indicating that the conversion should be applied
100 to an item of type char, short, int, or long, respectively.
101 Multiple types can be concatenated within the same
102 type_string and multiple −t options can be specified. Output
103 lines shall be written for each type specified in the order
104 in which the type specification characters are specified.
105 −v Write all input data. Without the −v option, any number of
107 groups of output lines, which would be identical to the imme‐
108 diately preceding group of output lines (except for the byte
109 offsets), shall be replaced with a line containing only an
110 <asterisk> ('*').
111 −x Interpret words (two-byte units) in hexadecimal. This shall
113 be equivalent to −t x2.
114 Multiple types can be specified by using multiple −bcdostx options.
116 Output lines are written for each type specified in the order in which
117 the types are specified.
118
120 The following operands shall be supported:
121 file A pathname of a file to be read. If no file operands are
123 specified, the standard input shall be used.
124 If there are no more than two operands, none of the −A, −j,
126 −N, −t, or −v options is specified, and either of the follow‐
127 ing is true: the first character of the last operand is a
128 <plus-sign> ('+'), or there are two operands and the first
129 character of the last operand is numeric; the last operand
130 shall be interpreted as an offset operand on XSI-conformant
131 systems. Under these conditions, the results are unspecified
132 on systems that are not XSI-conformant systems.
133 [+]offset[.][b]
135 The offset operand specifies the offset in the file where
136 dumping is to commence. This operand is normally interpreted
137 as octal bytes. If '.' is appended, the offset shall be
138 interpreted in decimal. If 'b' is appended, the offset shall
139 be interpreted in units of 512 bytes.
140
142 The standard input shall be used if no file operands are specified, and
143 shall be used if a file operand is '−' and the implementation treats
144 the '−' as meaning standard input. Otherwise, the standard input shall
145 not be used. See the INPUT FILES section.
146
148 The input files can be any file type.
149
151 The following environment variables shall affect the execution of od:
152 LANG Provide a default value for the internationalization vari‐
154 ables that are unset or null. (See the Base Definitions vol‐
155 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
156 ables for the precedence of internationalization variables
157 used to determine the values of locale categories.)
158 LC_ALL If set to a non-empty string value, override the values of
160 all the other internationalization variables.
161 LC_CTYPE Determine the locale for the interpretation of sequences of
163 bytes of text data as characters (for example, single-byte as
164 opposed to multi-byte characters in arguments and input
165 files).
166 LC_MESSAGES
168 Determine the locale that should be used to affect the format
169 and contents of diagnostic messages written to standard
170 error.
171 LC_NUMERIC
173 Determine the locale for selecting the radix character used
174 when writing floating-point formatted output.
175 NLSPATH Determine the location of message catalogs for the processing
177 of LC_MESSAGES.
178
180 Default.
181
183 See the EXTENDED DESCRIPTION section.
184
186 The standard error shall be used only for diagnostic messages.
187
189 None.
190
192 The od utility shall copy sequentially each input file to standard out‐
193 put, transforming the input data according to the output types speci‐
194 fied by the −t option or the −bcdosx options. If no output type is
195 specified, the default output shall be as if −t oS had been specified.
196 The number of bytes transformed by the output type specifier c may be
198 variable depending on the LC_CTYPE category.
199 The default number of bytes transformed by output type specifiers d, f,
201 o, u, and x corresponds to the various C-language types as follows. If
202 the c99 compiler is present on the system, these specifiers shall cor‐
203 respond to the sizes used by default in that compiler. Otherwise, these
204 sizes may vary among systems that conform to POSIX.1‐2008.
205 * For the type specifier characters d, o, u, and x, the default num‐
207 ber of bytes shall correspond to the size of the underlying imple‐
208 mentation's basic integer type. For these specifier characters, the
209 implementation shall support values of the optional number of bytes
210 to be converted corresponding to the number of bytes in the C-lan‐
211 guage types char, short, int, and long. These numbers can also be
212 specified by an application as the characters 'C', 'S', 'I', and
213 'L', respectively. The implementation shall also support the values
214 1, 2, 4, and 8, even if it provides no C-Language types of those
215 sizes. The implementation shall support the decimal value corre‐
216 sponding to the C-language type long long. The byte order used
217 when interpreting numeric values is implementation-defined, but
218 shall correspond to the order in which a constant of the corre‐
219 sponding type is stored in memory on the system.
220 * For the type specifier character f, the default number of bytes
222 shall correspond to the number of bytes in the underlying implemen‐
223 tation's basic double precision floating-point data type. The
224 implementation shall support values of the optional number of bytes
225 to be converted corresponding to the number of bytes in the C-lan‐
226 guage types float, double, and long double. These numbers can also
227 be specified by an application as the characters 'F', 'D', and 'L',
228 respectively.
229 The type specifier character a specifies that bytes shall be inter‐
231 preted as named characters from the International Reference Version
232 (IRV) of the ISO/IEC 646:1991 standard. Only the least significant
233 seven bits of each byte shall be used for this type specification.
234 Bytes with the values listed in the following table shall be written
235 using the corresponding names for those characters.
236 Table: Named Characters in od
238 ┌─────────────┬──────────────┬───────────────────┬──────────────┐
240 │Value Name │ Value Name │ Value Name │ Value Name │
241 ├─────────────┼──────────────┼───────────────────┼──────────────┤
242 │\000 nul │ \001 soh │ \002 stx │ \003 etx │
243 │\004 eot │ \005 enq │ \006 ack │ \007 bel │
244 │\010 bs │ \011 ht │ \012 lf or nl* │ \013 vt │
245 │\014 ff │ \015 cr │ \016 so │ \017 si │
246 │\020 dle │ \021 dc1 │ \022 dc2 │ \023 dc3 │
247 │\024 dc4 │ \025 nak │ \026 syn │ \027 etb │
248 │\030 can │ \031 em │ \032 sub │ \033 esc │
249 │\034 fs │ \035 gs │ \036 rs │ \037 us │
250 │\040 sp │ \177 del │ │ │
251 └─────────────┴──────────────┴───────────────────┴──────────────┘
252 Note: The "\012" value may be written either as lf or nl.
253 The type specifier character c specifies that bytes shall be inter‐
255 preted as characters specified by the current setting of the LC_CTYPE
256 locale category. Characters listed in the table in the Base Definitions
257 volume of POSIX.1‐2008, Chapter 5, File Format Notation ('\\', '\a',
258 '\b', '\f', '\n', '\r', '\t', '\v') shall be written as the correspond‐
259 ing escape sequences, except that <backslash> shall be written as a
260 single <backslash> and a NUL shall be written as '\0'. Other non-
261 printable characters shall be written as one three-digit octal number
262 for each byte in the character. Printable multi-byte characters shall
263 be written in the area corresponding to the first byte of the charac‐
264 ter; the two-character sequence "**" shall be written in the area cor‐
265 responding to each remaining byte in the character, as an indication
266 that the character is continued. When either the −j skip or −N count
267 option is specified along with the c type specifier, and this results
268 in an attempt to start or finish in the middle of a multi-byte charac‐
269 ter, the result is implementation-defined.
270 The input data shall be manipulated in blocks, where a block is defined
272 as a multiple of the least common multiple of the number of bytes
273 transformed by the specified output types. If the least common multiple
274 is greater than 16, the results are unspecified. Each input block shall
275 be written as transformed by each output type, one per written line, in
276 the order that the output types were specified. If the input block size
277 is larger than the number of bytes transformed by the output type, the
278 output type shall sequentially transform the parts of the input block,
279 and the output from each of the transformations shall be separated by
280 one or more <blank> characters.
281 If, as a result of the specification of the −N option or end-of-file
283 being reached on the last input file, input data only partially satis‐
284 fies an output type, the input shall be extended sufficiently with null
285 bytes to write the last byte of the input.
286 Unless −A n is specified, the first output line produced for each input
288 block shall be preceded by the input offset, cumulative across input
289 files, of the next byte to be written. The format of the input offset
290 is unspecified; however, it shall not contain any <blank> characters,
291 shall start at the first character of the output line, and shall be
292 followed by one or more <blank> characters. In addition, the offset of
293 the byte following the last byte written shall be written after all the
294 input data has been processed, but shall not be followed by any <blank>
295 characters.
296 If no −A option is specified, the input offset base is unspecified.
298
300 The following exit values shall be returned:
301 0 All input files were processed successfully.
303 >0 An error occurred.
305
307 Default.
308 The following sections are informative.
310
312 XSI-conformant applications are warned not to use filenames starting
313 with '+' or a first operand starting with a numeric character so that
314 the old functionality can be maintained by implementations, unless they
315 specify one of the −A, −j, or −N options. To guarantee that one of
316 these filenames is always interpreted as a filename, an application
317 could always specify the address base format with the −A option.
318
320 If a file containing 128 bytes with decimal values zero to 127, in
321 increasing order, is supplied as standard input to the command:
322 od −A d −t a
324 on an implementation using an input block size of 16 bytes, the stan‐
326 dard output, independent of the current locale setting, would be simi‐
327 lar to:
328 0000000 nul soh stx etx eot enq ack bel bs ht nl vt ff cr so si
330 0000016 dle dc1 dc2 dc3 dc4 nak syn etb can em sub esc fs gs rs us
331 0000032 sp ! " # $ % & ' ( ) * + , − . /
332 0000048 0 1 2 3 4 5 6 7 8 9 : ; < = > ?
333 0000064 @ A B C D E F G H I J K L M N O
334 0000080 P Q R S T U V W X Y Z [ \ ] ^ _
335 0000096 ` a b c d e f g h i j k l m n o
336 0000112 p q r s t u v w x y z { | } ~ del
337 0000128
338 Note that this volume of POSIX.1‐2008 allows nl or lf to be used as the
340 name for the ISO/IEC 646:1991 standard IRV character with decimal value
341 10. The IRV names this character lf (line feed), but traditional imple‐
342 mentations have referred to this character as newline (nl) and the
343 POSIX locale character set symbolic name for the corresponding charac‐
344 ter is a <newline>.
345 The command:
347 od −A o −t o2x2x −N 18
349 on a system with 32-bit words and an implementation using an input
351 block size of 16 bytes could write 18 bytes in approximately the fol‐
352 lowing format:
353 0000000 032056 031440 041123 042040 052516 044530 020043 031464
355 342e 3320 4253 4420 554e 4958 2023 3334
356 342e3320 42534420 554e4958 20233334
357 0000020 032472
358 353a
359 353a0000
360 0000022
361 The command:
363 od −A d −t f −t o4 −t x4 −N 24 −j 0x15
365 on a system with 64-bit doubles (for example, IEEE Std 754‐1985 double
367 precision floating-point format) would skip 21 bytes of input data and
368 then write 24 bytes in approximately the following format:
369 0000000 1.00000000000000e+00 1.57350000000000e+01
371 07774000000 00000000000 10013674121 35341217270
372 3ff00000 00000000 402f3851 eb851eb8
373 0000016 1.40668230000000e+02
374 10030312542 04370303230
375 40619562 23e18698
376 0000024
377
379 The od utility went through several names in early proposals, including
380 hd, xd, and most recently hexdump. There were several objections to
381 all of these based on the following reasons:
382 * The hd and xd names conflicted with historical utilities that
384 behaved differently.
385 * The hexdump description was much more complex than needed for a
387 simple dump utility.
388 * The od utility has been available on all historical implementations
390 and there was no need to create a new name for a utility so similar
391 to the historical od utility.
392 The original reasons for not standardizing historical od were also
394 fairly widespread. Those reasons are given below along with rationale
395 explaining why the standard developers believe that this version does
396 not suffer from the indicated problem:
397 * The BSD and System V versions of od have diverged, and the inter‐
399 section of features provided by both does not meet the needs of the
400 user community. In fact, the System V version only provides a mech‐
401 anism for dumping octal bytes and shorts, signed and unsigned deci‐
402 mal shorts, hexadecimal shorts, and ASCII characters. BSD added the
403 ability to dump floats, doubles, named ASCII characters, and octal,
404 signed decimal, unsigned decimal, and hexadecimal longs. The ver‐
405 sion presented here provides more normalized forms for dumping
406 bytes, shorts, ints, and longs in octal, signed decimal, unsigned
407 decimal, and hexadecimal; float, double, and long double; and named
408 ASCII as well as current locale characters.
409 * It would not be possible to come up with a compatible superset of
411 the BSD and System V flags that met the requirements of the stan‐
412 dard developers. The historical default od output is the specified
413 default output of this utility. None of the option letters chosen
414 for this version of od conflict with any of the options to histori‐
415 cal versions of od.
416 * On systems with different sizes for short, int, and long, there was
418 no way to ask for dumps of ints, even in the BSD version. Because
419 of the way options are named, the name space could not be extended
420 to solve these problems. This is why the −t option was added (with
421 type specifiers more closely matched to the printf() formats used
422 in the rest of this volume of POSIX.1‐2008) and the optional field
423 sizes were added to the d, f, o, u, and x type specifiers. It is
424 also one of the reasons why the historical practice was not man‐
425 dated as a required obsolescent form of od. (Although the old ver‐
426 sions of od are not listed as an obsolescent form, implementations
427 are urged to continue to recognize the older forms for several more
428 years.) The a, c, f, o, and x types match the meaning of the corre‐
429 sponding format characters in the historical implementations of od
430 except for the default sizes of the fields converted. The d format
431 is signed in this volume of POSIX.1‐2008 to match the printf()
432 notation. (Historical versions of od used d as a synonym for u in
433 this version. The System V implementation uses s for signed deci‐
434 mal; BSD uses i for signed decimal and s for null-terminated
435 strings.) Other than d and u, all of the type specifiers match for‐
436 mat characters in the historical BSD version of od.
437 The sizes of the C-language types char, short, int, long, float,
439 double, and long double are used even though it is recognized that
440 there may be zero or more than one compiler for the C language on
441 an implementation and that they may use different sizes for some of
442 these types. (For example, one compiler might use 2 bytes shorts, 2
443 bytes ints, and 4 bytes longs, while another compiler (or an option
444 to the same compiler) uses 2 bytes shorts, 4 bytes ints, and 4
445 bytes longs.) Nonetheless, there has to be a basic size known by
446 the implementation for these types, corresponding to the values
447 reported by invocations of the getconf utility when called with
448 system_var operands {UCHAR_MAX}, {USHORT_MAX}, {UINT_MAX}, and
449 {ULONG_MAX} for the types char, short, int, and long, respectively.
450 There are similar constants required by the ISO C standard, but not
451 required by the System Interfaces volume of POSIX.1‐2008 or this
452 volume of POSIX.1‐2008. They are {FLT_MANT_DIG}, {DBL_MANT_DIG},
453 and {LDBL_MANT_DIG} for the types float, double, and long double,
454 respectively. If the optional c99 utility is provided by the imple‐
455 mentation and used as specified by this volume of POSIX.1‐2008,
456 these are the sizes that would be provided. If an option is used
457 that specifies different sizes for these types, there is no guaran‐
458 tee that the od utility is able to interpret binary data output by
459 such a program correctly.
460 This volume of POSIX.1‐2008 requires that the numeric values of
462 these lengths be recognized by the od utility and that symbolic
463 forms also be recognized. Thus, a conforming application can always
464 look at an array of unsigned long data elements using od −t uL.
465 * The method of specifying the format for the address field based on
467 specifying a starting offset in a file unnecessarily tied the two
468 together. The −A option now specifies the address base and the −S
469 option specifies a starting offset.
470 * It would be difficult to break the dependence on US ASCII to
472 achieve an internationalized utility. It does not seem to be any
473 harder for od to dump characters in the current locale than it is
474 for the ed or sed l commands. The c type specifier does this with‐
475 out difficulty and is completely compatible with the historical
476 implementations of the c format character when the current locale
477 uses a superset of the ISO/IEC 646:1991 standard as a codeset. The
478 a type specifier (from the BSD a format character) was left as a
479 portable means to dump ASCII (or more correctly ISO/IEC 646:1991
480 standard (IRV)) so that headers produced by pax could be deciphered
481 even on systems that do not use the ISO/IEC 646:1991 standard as a
482 subset of their base codeset.
483 The use of "**" as an indication of continuation of a multi-byte char‐
485 acter in c specifier output was chosen based on seeing an implementa‐
486 tion that uses this method. The continuation bytes have to be marked in
487 a way that is not ambiguous with another single-byte or multi-byte
488 character.
489 An early proposal used −S and −n, respectively, for the −j and −N
491 options eventually selected. These were changed to avoid conflicts with
492 historical implementations.
493 The original standard specified −t o2 as the default when no output
495 type was given. This was changed to −t oS (the length of a short) to
496 accommodate a supercomputer implementation that historically used 64
497 bits as its default (and that defined shorts as 64 bits). This change
498 should not affect conforming applications. The requirement to support
499 lengths of 1, 2, and 4 was added at the same time to address an histor‐
500 ical implementation that had no two-byte data types in its C compiler.
501 The use of a basic integer data type is intended to allow the implemen‐
503 tation to choose a word size commonly used by applications on that
504 architecture.
505 Earlier versions of this standard allowed for implementations with
507 bytes other than eight bits, but this has been modified in this ver‐
508 sion.
509
511 All option and operand interfaces marked XSI may be removed in a future
512 version.
513
515 c99, sed
516 The Base Definitions volume of POSIX.1‐2008, Chapter 5, File Format
518 Notation, Chapter 8, Environment Variables, Section 12.2, Utility Syn‐
519 tax Guidelines
520
522 Portions of this text are reprinted and reproduced in electronic form
523 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
524 -- Portable Operating System Interface (POSIX), The Open Group Base
525 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
526 cal and Electronics Engineers, Inc and The Open Group. (This is
527 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
528 event of any discrepancy between this version and the original IEEE and
529 The Open Group Standard, the original IEEE and The Open Group Standard
530 is the referee document. The original Standard can be obtained online
531 at http://www.unix.org/online.html .
532 Any typographical or formatting errors that appear in this page are
534 most likely to have been introduced during the conversion of the source
535 files to man page format. To report such errors, see https://www.ker‐
536 nel.org/doc/man-pages/reporting_bugs.html .
537IEEE/The Open Group 2013 OD(1P)