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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 |
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NM(1P) POSIX Programmer's Manual NM(1P)
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.
nm — write the name list of an object file (DEVELOPMENT)
nm [-APv] [-g|-u] [-t format] file...
nm [-APv] [-efox] [-g|-u] [-t format] file...
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 if
the -P option is not specified.
The nm utility shall conform to the Base Definitions volume of
POSIX.1‐2017, 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 decimal (default if -P is not specified).
o octal.
x hexadecimal (default if -P is specified).
-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).
The following operand shall be supported:
file A pathname of an object file, executable file, or
object-file library.
See the INPUT FILES section.
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 POSIX.1‐2017, 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.
Default.
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
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:
"%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 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.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
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.
None.
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
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 <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 historical practice, and the requirement that implementation
additions also be single characters made parsing the information
easier for shell scripts.
None.
ar(1p), c99(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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 2017 NM(1P)
Pages that refer to this page: c99(1p), strings(1p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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