How can I get a list of the functions defined in a shared object library, or find out if a particular function is defined in one?
2 Answers
There are different executable file formats on a *nix system. a.out was a common format some years ago and today its ELF on nearby all major systems.
ELF consists of a headers describing each of the files data sections.
The part you are looking for is the symbol table, where each symbol (function, variable) is mapped to its address.
Shared libraries keep their global symbols in a section called .dynsym
What you are looking for are symbols of the type function and a global binding in this section.
readelf --syms ./libfoo.so will give you a output of the symbols.
On Solaris and FreeBSD theres also elfdump available.
objdump displays also a lot of information about your object file and you can specify a section by using the -j switch.
Use nm with the -D (dynamic) switch:
$ nm -D /usr/lib/libpng.so 00000000 A PNG12_0 w _Jv_RegisterClasses w __cxa_finalize U __fprintf_chk w __gmon_start__ U __longjmp_chk U __memcpy_chk U __snprintf_chk U __stack_chk_fail U _setjmp U abort U crc32 U deflate U deflateEnd U deflateInit2_ U deflateReset U fflush U fread U free U fwrite U gmtime U inflate U inflateEnd U inflateInit_ U inflateReset U malloc U memcmp U memcpy U memset 00003fd0 T png_access_version_number 00016ef0 T png_build_grayscale_palette 00004810 T png_check_sig 0001d2d0 T png_chunk_error 0001d070 T png_chunk_warning 00013390 T png_convert_from_struct_tm 00014a90 T png_convert_from_time_t 000048d0 T png_convert_to_rfc1123 000051b0 T png_create_info_struct 00013040 T png_create_read_struct 00012c20 T png_create_read_struct_2 00014a40 T png_create_write_struct 00014710 T png_create_write_struct_2 00004230 T png_data_freer 00005140 T png_destroy_info_struct 00010eb0 T png_destroy_read_struct 00013da0 T png_destroy_write_struct 0001d0f0 T png_error 0001ca10 T png_free 00004a50 T png_free_data 0001c9d0 T png_free_default ... 