nm -- Command

Print a program's symbol table
nm [ -adgnopru ] file ...

The command  nm prints the  symbol table of  each file. It  can read binary
files produced by the compiler, assembler, or linker.

When a C  source file is compiled with the  -c switch to the cc command, or
when a  file of  assembly language  is assembled, the  result is  an object
module, which is signified by the suffix .o.

The linker ld links multiple  object modules to form an executable program.
Frequently used object modules often are  grouped by the archiver ar into a
library, which is signified by the  suffix .a.  nm can read all three kinds
of files: .o, .a, and fully linked executables.

Options

nm recognizes the following options:

-a (COHERENT 286 only)
   Print all symbols.  Normally, nm prints names that are in C-style format
   and ignores symbols with names inaccessible from C programs.

-d Print only defined symbol.

-g Print only global symbols.

-n Sort numerically rather  than alphabetically.  nm uses unsigned compares
   when sorting symbols with this option.

-o Append the file name to the beginning of each output line.

-p Print symbols in the order in which they appear within the symbol table.

-r Sort in reverse-alphabetical order.

-u Print only undefined symbols.

Output Format

The output of nm is a series of lines of the form:

    segment address symbol

segment  gives  the segment  in  which  the symbol  appears,  or UNDEF  for
undefined symbols.   address is either  the address in  hexadecimal, or the
length of a common variable.  symbol names the symbol.

For example,  if foo.o is  a relocatable object  module, the output  of the
command nm -o foo.o would appears as follows:

    #nm foo.o
    UNDEF    00000000 _canl
    UNDEF    00000000 _stderr
    .text    0000077C acomp
    .text    00000034 acomp_old
    UNDEF    00000000 alloc
    .text    00000F28 archive
    .comm    00000004 asw
    .text    000003CC csymbol
    .comm    00000004 dsw

See Also

cc,
commands,
ld,
size,
strip

© 2012 by Stephen A. Ness