nm

List symbols from object files (POSIX)

Syntax:

nm [ -a ]  [ -g ]
   [ -B ]  [ -C ] [ -D ]
   [ -s ]  [ -A | -o ]
   [ -n | -v ]  [ -p ]
   [ -r ]  [ --size-sort ] [ -u ]
   [ -t radix ] [ -P ]
   [ --target=bfdname ] [ -f format ]
   [ --defined-only ] [-l ]
   [ --no-demangle ] [ -V ]  [ --help ]  
   [ objfile... ]

Options:

-A
-o

Precede each symbol by the name of the input file (or archive element) in which it was found, rather than identify the input file once only, before all of its symbols.

-a

Display all symbols, even debugger-only symbols; normally these aren't listed.

-B

The same as -f bsd (for compatibility with the MIPS nm).

-C

Decode (demangle) low-level symbol names into user-level names. Besides removing any initial underscore prepended by the system, this makes C++ function names readable.

-D

Display the dynamic symbols rather than the normal symbols. This is meaningful only for dynamic objects, such as certain types of shared libraries.

-f format

Use the output format format, which can be bsd, sysv, or posix. The default is bsd. Only the first character of format is significant; you can use either upper- or lowercase.

-g

Display only external symbols.

-l

("el") For each symbol, use debugging information to try to find a filename and line number. For a defined symbol, look for the line number of the address of the symbol. For an undefined symbol, look for the line number of a relocation entry that refers to the symbol. If line number information can be found, print it after the other symbol information.

-n
-v

Sort symbols numerically by their addresses, rather than alphabetically by their names.

-p

Don't bother to sort the symbols in any order; print them in the order encountered.

-P

Use the POSIX.2 standard output format instead of the default format. Equivalent to -f posix.

-r

Reverse the order of the sort (whether numeric or alphabetic); let the last come first.

-s

When listing symbols from archive members, include the index: a mapping (stored in the archive by ar) of which modules contain definitions for which names.

-t radix

Use radix as the radix for printing the symbol values. It must be d for decimal, o for octal, or x for hexadecimal.

-u

Display only undefined symbols (those external to each object file).

-V

Show the version number of nm and exit.

GNU extensions

--defined-only

Display only defined symbols for each object file.

--help

Show a summary of the options to nm and exit.

--no-demangle

Don't demangle low-level symbol names. This is the default.

--size-sort

Sort symbols by size. The size is computed as the difference between the value of the symbol and the value of the symbol with the next higher value. The size of the symbol is printed, rather than the value.

--target=bfdname

Specify an object code format other than your system's default format. For more information, see "Target Selection" in the appendix Selecting the Target System.

Description:

The nm utility lists the symbols from the specified object files. If no object files are listed as arguments, nm assumes a.out.

For each symbol, nm shows:

• The symbol value, in the radix selected by options (see below), or hexadecimal by default.
• The symbol type. At least the following types are used; others are, as well, depending on the object file format. If lowercase, the symbol is local; if uppercase, the symbol is global (external).

  A

  The symbol's value is absolute, and isn't changed by further linking.

  B

  The symbol is in the uninitialized data section (known as BSS).

  C

  The symbol is common. Common symbols are uninitialized data. When linking, multiple common symbols may appear with the same name. If the symbol is defined anywhere, the common symbols are treated as undefined references. For more details on common symbols, see the discussion of the --warn-common option for ld.

  D

  The symbol is in the initialized data section.

  G

  The symbol is in an initialized data section for small objects. Some object file formats permit more efficient access to small data objects, such as a global int variable, as opposed to a large global array.

  I

  The symbol is an indirect reference to another symbol. This is a GNU extension to the a.out object file format that's rarely used.

  N

  The symbol is a debugging symbol.

  R

  The symbol is in a read-only data section.

  S

  The symbol is in an uninitialized data section for small objects.

  T

  The symbol is in the text (code) section.

  U

  The symbol is undefined.

  W

  The symbol is weak. When a weak defined symbol is linked with a normal defined symbol, the normal defined symbol is used with no error. When a weak undefined symbol is linked and the symbol isn't defined, the value of the weak symbol becomes zero with no error.

  -

  The symbol is a stabs symbol in an a.out object file. In this case, the next values printed are parts of the stabs information for the symbol. Stabs symbols are used to hold debugging information; for more information, see "Stabs Overview" in The stabs debug format in the full online GNU documentation.

  ?

  The symbol type is unknown, or specific to the object file format.

• The symbol name.

Author:

GNU

See also:

ar