This utility shall be provided on systems that support both the User
Portability Utilities option and the Software Development
Utilities option. On other systems it is optional. Certain options
are only available on XSI-conformant systems.
The nm utility shall display symbolic information appearing
in the object file, executable file, or object-file library
named by file. If no symbolic information is available for a
valid input file, the nm utility shall report that fact,
but not consider it an error condition.
The default base used when numeric values are written is unspecified.
On XSI-conformant systems, it shall be decimal.
The input file shall be an object file, an object-file library whose
format is the same as those produced by the ar utility for link
editing, or an executable file. The nm utility may accept additional
implementation-defined object library formats for the input file.
The following environment variables shall affect the execution of
nm:
LANG
Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, 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_COLLATE
Determine the locale for character collation information for the symbol-name
and symbol-value collation sequences.
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).
LC_MESSAGES
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
NLSPATH
Determine the location of message catalogs for the processing of LC_MESSAGES
.
If symbolic information is present in the input files, then for each
file or for each member of an archive, the nm
utility shall write the following information to standard output.
By default, the format is unspecified, but the output shall be
sorted alphabetically by symbol name:
*
Library or object name, if -A is specified
*
Symbol name
*
Symbol type, which shall either be one of the following single characters
or an implementation-defined type represented by a
single character:
A
Global absolute symbol.
a
Local absolute symbol.
B
Global "bss" (that is, uninitialized data space) symbol.
b
Local bss symbol.
D
Global data symbol.
d
Local data symbol.
T
Global text symbol.
t
Local text symbol.
U
Undefined symbol.
*
Value of the symbol
*
The size associated with the symbol, if applicable
This information may be supplemented by additional information specific
to the implementation.
If the -P option is specified, the previous information shall
be displayed using the following portable format. The three
versions differ depending on whether -t d, -t o, or
-t x was specified, respectively:
where <library/object name> shall be formatted as follows:
*
If -A is not specified, <library/object name> shall be
an empty string.
*
If -A is specified and the corresponding file operand
does not name a library:
"%s: ", <file>
*
If -A is specified and the corresponding file operand
names a library. In this case,
<object file> shall name the object file in the library containing
the symbol being described:
"%s[%s]: ", <file>, <object file>
If -A is not specified, then if more than one file operand
is specified or if only one file operand is
specified and it names a library, nm shall write a line identifying
the object containing the following symbols before the
lines containing those symbols, in the form:
*
If the corresponding file operand does not name a library:
"%s:\n", <file>
*
If the corresponding file operand names a library; in this case,
<object file> shall be the name of the
file in the library containing the following symbols:
"%s[%s]:\n", <file>, <object file>
If -P is specified, but -t is not, the format shall be
as if -t x had been specified.
Mechanisms for dynamic linking make this utility less meaningful when
applied to an executable file because a dynamically linked
executable may omit numerous library routines that would be found
in a statically linked executable.
Historical implementations of nm have used different bases for
numeric output and supplied different default types of
symbols that were reported. The -tformat option, similar
to that used in od and strings, can be used to specify
the numeric
base; -g and -u can be used to restrict the amount of
output or the types of symbols included in the output.
The compromise of using -tformatversus using -d,
-o, and other similar options was
necessary because of differences in the meaning of -o between
implementations. The -o option from BSD has been
provided here as -A to avoid confusion with the -o from
System V (which has been provided here as -t and as
-o on XSI-conformant systems).
The option list was significantly reduced from that provided by historical
implementations.
The nm description is a subset of both the System V and BSD
nm utilities with no specified default output.
It was recognized that mechanisms for dynamic linking make this utility
less meaningful when applied to an executable file
(because a dynamically linked executable file may omit numerous library
routines that would be found in a statically linked
executable file), but the value of nm during software development
was judged to outweigh other limitations.
The default output format of nm is not specified because of
differences in historical implementations. The -P
option was added to allow some type of portable output format. After
a comparison of the different formats used in SunOS, BSD,
SVR3, and SVR4, it was decided to create one that did not match the
current format of any of these four systems. The format devised
is easy to parse by humans, easy to parse in shell scripts, and does
not need to vary depending on locale (because no English
descriptions are included). All of the systems currently have the
information available to use this format.
The format given in nm STDOUT uses spaces between the fields,
which may be any number of <blank>s required to align
the columns. The single-character types were selected to match historical
practice, and the requirement that implementation
additions also be single characters made parsing the information easier
for shell scripts.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
IEEE/The Open Group
NM (P)
2003
Generated by OpenAsthra.com from man1p/nm.1p using man macros.
