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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 (con-
sult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on
Linux.

NAME
nm - write the name list of an object file (DEVELOPMENT)

SYNOPSIS
nm [-APv][-efox][ -g| -u][-t format] file...

DESCRIPTION
This utility shall be provided on systems that support both the User Portability Utilities option and the Software Devel-
opment 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.

OPTIONS
The nm utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guide-
lines.

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 alphabetically.

-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 util-
ity for link editing, or an executable file. The nm utility may accept additional implementation-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 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 international-
ization 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 stan-
dard 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 util-
ity 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 repre-
sented 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 contain-
ing 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.

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 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.

FUTURE DIRECTIONS
None.