How to List the Symbols in a .So File

How do I list the symbols in a .so file

The standard tool for listing symbols is nm, you can use it simply like this:

nm -gD yourLib.so

If you want to see symbols of a C++ library, add the "-C" option which demangle the symbols (it's far more readable demangled).

nm -gDC yourLib.so

If your .so file is in elf format, you have two options:

Either objdump (-C is also useful for demangling C++):

$ objdump -TC libz.so

libz.so:     file format elf64-x86-64

DYNAMIC SYMBOL TABLE:
0000000000002010 l    d  .init  0000000000000000              .init
0000000000000000      DF *UND*  0000000000000000  GLIBC_2.2.5 free
0000000000000000      DF *UND*  0000000000000000  GLIBC_2.2.5 __errno_location
0000000000000000  w   D  *UND*  0000000000000000              _ITM_deregisterTMCloneTable

Or use readelf:

$ readelf -Ws libz.so
Symbol table '.dynsym' contains 112 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000002010     0 SECTION LOCAL  DEFAULT   10
     2: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND free@GLIBC_2.2.5 (14)
     3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __errno_location@GLIBC_2.2.5 (14)
     4: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_deregisterTMCloneTable

nm - show file that declares a symbol in a .so file

If I compile this file into a shared object file, file.so, I should get a "U" for the get_data symbol

You are mistaken: since nothing references get_data, you wouldn't in fact get a U for it.

To answer your question: the info that file.cpp referenced get_data symbol is gone, unless you compiled file.cpp with debugging info.

If you did, you could use objdump -dS file.so to find that file.cpp is where the reference originates.

How do I find out what all symbols are exported from a shared object?

Do you have a "shared object" (usually a shared library on AIX), a UNIX shared library, or a Windows DLL? These are all different things, and your question conflates them all :-(

• For an AIX shared object, use dump -Tv /path/to/foo.o.
• For an ELF shared library, use readelf -Ws --dyn-syms /path/to/libfoo.so, or (if you have GNU nm) nm -D /path/to/libfoo.so.
• For a non-ELF UNIX shared library, please state which UNIX you are interested in.
• For a Windows DLL, use dumpbin /EXPORTS foo.dll.

How can I look inside a Linux .so or .a object and see what functions they contain?

you can do nm Linux.so and it'll show the functions and variables inside the .so file.

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