ldd - print shared object dependencies
ldd [
option]...
file...
ldd prints the shared objects (shared libraries) required by each program
or shared object specified on the command line. An example of its use and
output is the following:
$ ldd /bin/ls
linux-vdso.so.1 (0x00007ffcc3563000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f87e5459000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f87e5254000)
libc.so.6 => /lib64/libc.so.6 (0x00007f87e4e92000)
libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f87e4c22000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f87e4a1e000)
/lib64/ld-linux-x86-64.so.2 (0x00005574bf12e000)
libattr.so.1 => /lib64/libattr.so.1 (0x00007f87e4817000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f87e45fa000)
In the usual case,
ldd invokes the standard dynamic linker (see
ld.so(8)) with the
LD_TRACE_LOADED_OBJECTS environment variable
set to 1. This causes the dynamic linker to inspect the program's dynamic
dependencies, and find (according to the rules described in
ld.so(8))
and load the objects that satisfy those dependencies. For each dependency,
ldd displays the location of the matching object and the (hexadecimal)
address at which it is loaded. (The
linux-vdso and
ld-linux
shared dependencies are special; see
vdso(7) and
ld.so(8).)
Be aware that in some circumstances (e.g., where the program specifies an ELF
interpreter other than
ld-linux.so), some versions of
ldd may
attempt to obtain the dependency information by attempting to directly execute
the program, which may lead to the execution of whatever code is defined in
the program's ELF interpreter, and perhaps to execution of the program itself.
(In glibc versions before 2.27, the upstream
ldd implementation did
this for example, although most distributions provided a modified version that
did not.)
Thus, you should
never employ
ldd on an untrusted executable,
since this may result in the execution of arbitrary code. A safer alternative
when dealing with untrusted executables is:
$ objdump -p /path/to/program | grep NEEDED
Note, however, that this alternative shows only the direct dependencies of the
executable, while
ldd shows the entire dependency tree of the
executable.
- --version
- Print the version number of ldd.
- -v, --verbose
- Print all information, including, for example, symbol versioning
information.
- -u, --unused
- Print unused direct dependencies. (Since glibc 2.3.4.)
- -d, --data-relocs
- Perform relocations and report any missing objects (ELF only).
- -r, --function-relocs
- Perform relocations for both data objects and functions, and report any
missing objects or functions (ELF only).
- --help
- Usage information.
ldd does not work on a.out shared libraries.
ldd does not work with some extremely old a.out programs which were built
before
ldd support was added to the compiler releases. If you use
ldd on one of these programs, the program will attempt to run with
argc = 0 and the results will be unpredictable.
pldd(1),
sprof(1),
ld.so(8),
ldconfig(8)