NM(1P) POSIX Programmer's Manual NM(1P)PROLOG
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.
NAMEnm — write the name list of an object file (DEVELOPMENT)
SYNOPSISnm [−APv] [−g|−u] [−t format] file...
nm [−APv] [−efox] [−g|−u] [−t format] file...
DESCRIPTION
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.
OPTIONS
The nm utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
−A Write the full pathname or library name of an object on each
line.
−e Write only external (global) and static symbol information.
−f Produce full output. Write redundant symbols (.text, .data,
and .bss), normally suppressed.
−g Write only external (global) symbol information.
−o Write numeric values in octal (equivalent to −t o).
−P Write information in a portable output format, as specified
in the STDOUT section.
−t format Write each numeric value in the specified format. The format
shall be dependent on the single character used as the format
option-argument:
d The offset is written in decimal (default).
o The offset is written in octal.
x The offset is written in hexadecimal.
−u Write only undefined symbols.
−v Sort output by value instead of by symbol name.
−x Write numeric values in hexadecimal (equivalent to −t x).
OPERANDS
The following operand shall be supported:
file A pathname of an object file, executable file, or object-file
library.
STDIN
See the INPUT FILES section.
INPUT FILES
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 edit‐
ing, or an executable file. The nm utility may accept additional imple‐
mentation-defined object library formats for the input file.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of nm:
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables 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.
ASYNCHRONOUS EVENTS
Default.
STDOUT
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 by symbol name according to
the collation sequence in the current locale.
* 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 sin‐
gle 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 dis‐
played using the following portable format. The three versions differ
depending on whether −t d, −t o, or −t x was specified, respectively:
"%s%s %s %d %d\n", <library/object name>, <name>, <type>,
<value>, <size>
"%s%s %s %o %o\n", <library/object name>, <name>, <type>,
<value>, <size>
"%s%s %s %x %x\n", <library/object name>, <name>, <type>,
<value>, <size>
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 sym‐
bols 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 contain‐
ing 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.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
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.
EXAMPLES
None.
RATIONALE
Historical implementations of nm have used different bases for numeric
output and supplied different default types of symbols that were
reported. The −t format 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 −t format versus using −d, −o, and other simi‐
lar 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 pro‐
vided here as −t and as −o on XSI-conformant systems).
The option list was significantly reduced from that provided by histor‐
ical implementations.
The nm description is a subset of both the System V and BSD nm utili‐
ties 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 dynami‐
cally 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 limita‐
tions.
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 Eng‐
lish descriptions are included). All of the systems currently have the
information available to use this format.
The format given in nm STDOUT uses <space> characters between the
fields, which may be any number of <blank> characters required to align
the columns. The single-character types were selected to match histori‐
cal practice, and the requirement that implementation additions also be
single characters made parsing the information easier for shell
scripts.
FUTURE DIRECTIONS
None.
SEE ALSO
ar, c99
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
COPYRIGHT
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 Electri‐
cal 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.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 NM(1P)
