nm(1) — Commands
NAME
nm − Name list dump of object files
SYNOPSIS
nm [−B|-P|-S] [-AabdfhnoprTVvwx] [−e|-g|-u] [−t format]
[−mangled_name_only]
[−mangled_name_also] [file ...]
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
nm: XPG4, XPG4−UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
FLAGS
The nm command accepts both XPG4−UNIX standard options and Digital extensions.
The following flags control the format of the output:
defaultPrints output in OSF format.
−B[Digital] Prints output in Berkeley (4.3 BSD) format. This format produces an address or value field followed by a letter showing what section the symbol is located in. The third and final field is the name of the symbol.
−PPrints output in a portable (POSIX) format. This format prints lines containing each symbol’s name, type (single letter), value, and size.
−S[Digital] Prints output in System V format.
The following flags control the contents of the output, how sorting is done, and how numeric values are printed. Note that the format that is in effect influences the results of many of these flags:
−APrints the full pathname or library name of an object on each line.
−a[Digital] Prints full debugging information.
−b[Digital] For Berkeley (−B) format only, prints the value field in octal. Equivalent to −t o.
−d[Digital] Prints the value field in decimal. Equivalent to −t d.
−ePrints only external and static symbol information.
−gPrints only external symbol information.
−h[Digital] Suppresses the printing of headers.
−n[Digital] For Berkeley (−B) format, sorts all symbols by value. For System V (−S) format, sorts external symbols by name. For other formats, sorts all symbols by name.
−oPrints numeric values in octal (equivalent to −t o).
[Digital] For Berkeley format (-B), prepends the filename to each symbol (equivalent to −A).
−p[Digital] Prints symbols in the order in which they are found in the file.
−r[Digital] Reverses the order of a value or name sort.
−T[Digital] Truncates long names, inserting an asterisk (∗) as the last printed character.
−t format
Writes each numeric value in the specified format as follows:
dThe offset is written in decimal. Equivalent to -d.
oThe offset is written in octal. Equivalent to -o.
xThe offset is written in hexadecimal. Equivalent to -x.
−uPrints only undefined symbols.
−V[Digital] Prints version information on stderr.
−vSorts output by value instead of alphabetically.
[Digital] For System V format (-S), sorts external symbols by value.
−w[Digital] Identifies weak symbols using an asterisk (∗). For the default, portable (−P), and Berkeley (−B) formats, the asterisk follows the symbol type letter. For System V (−S), an additional column is added to the end of each line containing an asterisk for weak symbols.
−xPrints numeric values in hexadecimal. Equivalent to −t x.
[Digital] The DEC C++ compiler encodes type information in function, template, variable, and virtual table names to enable type-safe linkages. This encoding is called "name mangling." The following options can be used to instruct the nm command to print either the original name (that is, the demangled name), the mangled name, or both, by specifying one of the following flags. By default, nm shows the demangled names only.
−mangled_name_only
[Digital] Prints only the mangled name.
−mangled_name_also
[Digital] Prints both the mangled and the demangled names.
DESCRIPTION
The nm command prints formatted listings of the symbol and external sections of an object file symbol table. A file can be an object file, an archive library, or a shared library. If you do not specify a file, this command assumes a.out.
The nm tool supports four output formats:
−OSF (the default)
−[Digital] Berkeley 4.3 BSD (−B flag)
−[Digital] System V (−S flag)
−Portable (−P flag)
The following default behaviors are the same for all four formats:
−Sort by name
−Show external and static symbols
−Output in hexadecimal
The only exception to these defaults is that numbers in OSF format are in decimal by default.
Each format has a distinctive output style and can influence the results of some of the options that affect content, how sorting is done, and how numeric values are printed, as explained in the FLAGS section.
Output
If symbolic information is present in the input files, nm writes the following information for each file or archive member by default:
−Symbol name
−Value of the symbol
−Symbol type
−Size associated with the symbol, if applicable
For example:
Name Value Type Size
_gp | 0000005368742016 | A | 0000000000000008
exit | 0000004831842368 | U | 0000000000000008
main | 0000004831842816 | T | 0000000000000008
For the default, portable (-P), and Berkeley (-B) formats, single characters are used as an abbreviation for symbol types. Uppercase characters represent external symbols, and lowercase letters represent local symbols.
The symbol types and their abbreviations are as follows:
AExternal absolute
aLocal absolute
BExternal zeroed data
bLocal zeroed data
C[Digital] Common
DExternal initialized data
dLocal initialized data
E[Digital] Small common
G[Digital] External small initialized data
g[Digital] Local small initialized data
H [Digital] TLS common
J[Digital] TLS initialized data
K[Digital] TLS zeroed data
N[Digital] Nil storage class, compiler internal usage
Q[Digital] Read-only constants
q[Digital] Local read-only constants
R[Digital] External read-only data
r[Digital] Local read-only data
S[Digital] External small zeroed data
s[Digital] Local small zeroed data
TExternal text
tLocal text
UExternal undefined
V[Digital] External small undefined
Z[Digital] No storage allocated
[Digital] If the −a option is specified, an expanded listing in System V format is written, formatted with the following columns:
Name The symbol or external name
ValueValue field for the symbol or external, usually an address or interesting debugging information
ClassThe symbol type
TypeThe symbol’s declaration
SizeThe symbol’s size
IndexThe symbol’s index field
SectionThe symbol’s storage class
RELATED INFORMATION
Guides: Programmer’s Guide, Assembly Language Programmer’s Guide
Standards: standards(5)