List symbols from object files (POSIX)
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... ]
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.
- Display all symbols, even debugger-only symbols; normally these aren't
- The same as -f bsd (for compatibility with the MIPS nm).
- 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.
- Display the dynamic symbols rather than the normal symbols. This is
meaningful only for dynamic objects, such as certain types of shared
- -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.
- Display only external symbols.
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.
- Sort symbols numerically by their addresses, rather than alphabetically
by their names.
- Don't bother to sort the symbols in any order; print them in the order
- Use the POSIX.2 standard output format instead of the default format.
Equivalent to -f posix.
- Reverse the order of the sort (whether numeric or alphabetic); let the
last come first.
- 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
- Display only undefined symbols (those external to each object file).
- Show the version number of nm and exit.
- Display only defined symbols for each object file.
- Show a summary of the options to nm and exit.
- Don't demangle low-level symbol names. This is the default.
- 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.
Specify an object code format other than your system's default format.
For more information, see
in the appendix Selecting the Target System.
The nm utility
lists the symbols from the specified object files.
If no object files are listed as arguments, nm assumes
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).
- The symbol's value is absolute, and isn't changed by further
- The symbol is in the uninitialized data section (known as BSS).
- 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
- The symbol is in the initialized data section.
- 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.
- 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.
- The symbol is a debugging symbol.
- The symbol is in a read-only data section.
- The symbol is in an uninitialized data section for small objects.
- The symbol is in the text (code) section.
- The symbol is undefined.
- 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
- The symbol type is unknown, or specific to the object file format.
- The symbol name.