od.html

unix 下的C开发手册,还用详细的例程。

The number of bytes transformed by the output type specifier
c
may be variable depending on the LC_CTYPE category.
<p>
The default number of bytes transformed by output type specifiers
d,
f,
o,
u
and
x
will correspond to the various C-language types as follows.
If the
<i><a href="c89.html">c89</a></i>
compiler is present on the system, these specifiers
will correspond to the sizes used by default in that compiler.
Otherwise, these sizes are implementation-dependent.
<ul>
<p>
<li>
For the type specifier characters
d,
o,
u
and
x,
the default number of
bytes will correspond to the size of the
underlying implementation's basic integral data type.
For these specifier characters,
the implementation will support values of the
optional number of bytes to be converted corresponding to the number of
bytes in the C-language types
<b>char</b>,
<b>short</b>,
<b>int</b>
and
<b>long.</b>
These numbers can also be specified by an application as
the characters
C,
S,
I
and
L,
respectively.
The byte order
used when interpreting numeric values
is implementation-dependent, but
will correspond to the order in which a constant of the corresponding
type is stored in memory on the system.
<br>
<p>
<li>
For the type specifier character
f,
the default number of bytes
will correspond to the number of bytes in
the underlying
implementation's basic double precision floating-point data type.
The implementation will support values of
the optional number of bytes to be
converted corresponding to the number of bytes in the C-language types
<b>float,</b>
<b>double</b>
and
<b>long double</b>.
These numbers can also be
specified by an application as the characters
F,
D
and
L,
respectively.
<p>
</ul>
<p>
The type specifier character
a
specifies that bytes are interpreted
as named characters from the
International Reference Version (IRV) of the ISO/IEC&nbsp;646:1991 standard.
Only the least significant seven bits of each byte will be used for
this type specification.
Bytes with the values listed in the following table
will be written using the corresponding names for those characters.
<br>
<p><table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Value</b>
<th align=center><b>Name</b>
<th align=center><b>Value</b>
<th align=center><b>Name</b>
<th align=center><b>Value</b>
<th align=center><b>Name</b>
<th align=center><b>Value</b>
<th align=center><b>Name</b>
<tr valign=top><td align=left>\000
<td align=left><b>nul</b>
<td align=left>\001
<td align=left><b>soh</b>
<td align=left>\002
<td align=left><b>stx</b>
<td align=left>\003
<td align=left><b>etx</b>
<tr valign=top><td align=left>\004
<td align=left><b>eot</b>
<td align=left>\005
<td align=left><b>enq</b>
<td align=left>\006
<td align=left><b>ack</b>
<td align=left>\007
<td align=left><b>bel</b>
<tr valign=top><td align=left>\010
<td align=left><b>bs</b>
<td align=left>\011
<td align=left><b>ht</b>
<td align=left>\012
<td align=left><b>lf or nl<sup><small>*</small></sup></b>
<td align=left>\013
<td align=left><b>vt</b>
<tr valign=top><td align=left>\014
<td align=left><b>ff</b>
<td align=left>\015
<td align=left><b>cr</b>
<td align=left>\016
<td align=left><b>so</b>
<td align=left>\017
<td align=left><b>si</b>
<tr valign=top><td align=left>\020
<td align=left><b>dle</b>
<td align=left>\021
<td align=left><b>dc1</b>
<td align=left>\022
<td align=left><b>dc2</b>
<td align=left>\023
<td align=left><b>dc3</b>
<tr valign=top><td align=left>\024
<td align=left><b>dc4</b>
<td align=left>\025
<td align=left><b>nak</b>
<td align=left>\026
<td align=left><b>syn</b>
<td align=left>\027
<td align=left><b>etb</b>
<tr valign=top><td align=left>\030
<td align=left><b>can</b>
<td align=left>\031
<td align=left><b>em</b>
<td align=left>\032
<td align=left><b>sub</b>
<td align=left>\033
<td align=left><b>esc</b>
<tr valign=top><td align=left>\034
<td align=left><b>fs</b>
<td align=left>\035
<td align=left><b>gs</b>
<td align=left>\036
<td align=left><b>rs</b>
<td align=left>\037
<td align=left><b>us</b>
<tr valign=top><td align=left>\040
<td align=left><b>sp</b>
<td align=left>\177
<td align=left><b>del</b>
<td align=left>&nbsp;
<td align=left>&nbsp;
<td align=left>&nbsp;
<td align=left>&nbsp;
</table>
<h6 align=center><xref table="Named Characters in <I>od</i>"></xref>Table: Named Characters in <i>od</i></h6>
<dl><dt><b>Note:</b>
<dd>The
<b>\012</b>
value may be written either as
<b>lf</b>
or
<b>nl</b>.
</dl>
<p>
The type specifier character
c
specifies that bytes will be interpreted
as characters specified by the current setting of the LC_CTYPE locale category.
Characters listed in the table in
the <b>XBD</b> specification, <a href="../xbd/notation.html"><b>File Format Notation</b>&nbsp;</a> 
(\\,
\a,
\b,
\f,
\n,
\r,
\t,
\v)
will be written as
the corresponding escape sequences, except that backslash will be
written as a single backslash
and a NUL will be written as
\0.
Other non-printable characters will be
written as one three-digit octal number
for each byte in the character.
If the size of a byte on the system is greater than nine bits,
the format used for non-printable characters is implementation-dependent.
Printable multi-byte characters will be written
in the area corresponding to the first byte of the character; the
two-character sequence
**
will be written in the area corresponding to
each remaining byte in the character, as an indication that the character
is continued.
When either the
<b>-j</b>&nbsp;<i>skip</i>
or
<b>-N</b>&nbsp;<i>count</i>
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-dependent.
<p>
The input data is 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 will 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 will sequentially transform the parts of the input block, and
the output from each of the transformations will be separated by one or
more
blank characters.
<p>
If, as a result of the specification of the
<b>-N</b>
option or end-of-file
being reached on the last input file,
input data only partially satisfies
an output type, the input will be extended sufficiently with null bytes
to write the last byte of the input.
<p>
Unless
<b>-A n</b>
is specified, the first output line produced for each input
block will 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 will not contain any
blank characters,
will start at the
first character of the output line, and will be
followed by one or more
blank characters.
In addition, the offset of the byte following the last byte written
will be written after all the input data has been processed, but will not
be followed by any
blank characters.
<p>
If no
<b>-A</b>
option is specified, the input offset base is unspecified.
</blockquote><h4><a name = "tag_001_014_1606">&nbsp;</a>EXIT STATUS</h4><blockquote>
The following exit values are returned:
<dl compact>

<dt>0<dd>All input files were processed successfully.

<dt>&gt;0<dd>An error occurred.

</dl>
</blockquote><h4><a name = "tag_001_014_1607">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>
Default.
</blockquote><h4><a name = "tag_001_014_1608">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
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 new options specified by the ISO/IEC 9945-2:1993 standard.
To guarantee that one of these
filenames will always be interpreted as a filename, an
application could always specify the address base format with the
<b>-A</b>
option.
</blockquote><h4><a name = "tag_001_014_1609">&nbsp;</a>EXAMPLES</h4><blockquote>
If a file containing 128 bytes with decimal values zero to
127, in increasing order, is supplied as standard input to the command:
<pre>
<code>
od -A d -t a
</code>
</pre>
on an implementation using an input block size of 16 bytes, the
standard output, independent of the current locale setting,
would be similar to:
<pre>
<code>
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   !   "   #   $   %   &amp;   '   (   )   *   +   ,   -   .   /
0000048   0   1   2   3   4   5   6   7   8   9   :   ;   &lt;   =   &gt;   ?
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
</code>
</pre>
<p>
Note that this specification allows
<b>nl</b>
or
<b>lf</b>
to be used as the name for the ISO/IEC&nbsp;646:1991 standard
IRV character with decimal value 10.
The IRV names this character
<b>lf</b>
(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 character.
<p>
The command:
<pre>
<code>
od -A o -t o2x2x -n 18
</code>
</pre>
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:
<pre>
<code>
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
</code>
</pre>
<p>
The command:
<pre>
<code>
od -A d -t f -t o4 -t x4 -n 24 -j 0x15
</code>
</pre>
on a system with 64-bit doubles (for example, the IEEE Std. 754 double
precision floating-point format) would skip 21 bytes of input data and
then write 24 bytes in approximately the following format:
<pre>
<code>
0000000    1.00000000000000e+00    1.57350000000000e+01
        07774000000 00000000000 10013674121 35341217270
           3ff00000    00000000    402f3851    eb851eb8
0000016    1.40668230000000e+02
        10030312542 04370303230
           40619562    23e18698
0000024
</code>
</pre>
</blockquote><h4><a name = "tag_001_014_1610">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
All option and operand interfaces marked as extensions may be
withdrawn in a future issue.
<p>
The IEEE PASC 1003.2 Interpretations Committee has forwarded concerns about
parts of this interface definition to the IEEE PASC 1003.2 Interpretations Committee
which is identifying the corrections.
A future revision of this specification will align with
IEEE Std. 1003.2b when finalised.
</blockquote><h4><a name = "tag_001_014_1611">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="sed.html">sed</a></i>.
</blockquote><hr size=2 noshade>
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