Using the 'ldd' Command in Linux

Find the software libraries your programs are using

Use the ldd command to show the shared libraries required by any given program. The ldd command is useful for working out when there is a missing dependency. The command also lists missing functions and objects.

ldd Command Syntax

Observe the proper syntax for the ldd command to avoid errors:

ldd [OPTION]... FILE...

Use one or more of the available ldd command switches, inserted into the [OPTION] spot in the above command:

  • --help: Print this help and exit.
  • --version: Print version information and exit.
  • -d, --data-relocs: Process data relocations.
  • -r, --function-relocs: Process data and function relocations.
  • -u, --unused: Print unused direct dependencies.
  • -v, --verbose: Print all information.

How to Use the ldd Command

Execute the following command to get more information about a program:

ldd -v /path/to/program/executable

The output shows version information as well as the paths and addresses to the shared libraries, like this:

libshared.so
linux-vdso.so.1 => (0x00007fff26ac8000)
libc.so.6 => /lib/libc.so.6 0x00007ff1df55a000)
/lib64/ld-linux-x86-64.so.2 (0x00007ff1dfafe000)
Linux ldd command

If the SO file doesn't exist at all, you can find the missing libraries using the following command:

ldd -d path/to/program

The output is similar to the following:

linux-vdso.so.1 (0x00007ffc2936b000)
/home/gary/demo/garylib.so => not foundlibc.so.6 => usr/lib/libc.so.6 (0x00007fd0c6259000)
/lib64/ld-linux-x86-64.so.2 (0x00007fd0c65fd000)
Linux ldd command missing

Never run the ldd command against an untrusted program because the ldd command might execute it. Instead, use a safer alternative that shows the direct dependencies only and not the whole dependency tree:

objdump -p /path/to/program | grep NEEDED
Linux objdump ldd alternative

How to Find the Path to an Application

You have to provide the full path to an application if you want to find its dependencies with ldd, which you can do in several ways.

For example, this is how to find the path to Firefox:

find / -name firefox

The problem with the find command, however, is that it lists the executable and everywhere that Firefox is located, like this:

/etc/skel/.mozilla/firefox
/home//cache/mozilla/firefox
/home//.mozilla/firefox
/usr/bin/Firefox
/usr/lib/Firefox
/usr/lib/Firefox/Firefox

This approach is a bit of an overkill and you may need to use the sudo command to elevate your privileges, else you're likely to get man permission-denied errors.

It's instead easier to use the whereis command to find an application's path:

whereis firefox

This time the output might look like this:

/usr/bin/firefox
/etc/firefox
/usr/lib/firefox
Linux whereis command

Then, to find the shared libraries for Firefox, enter the following command:

ldd /usr/bin/firefox

The output from the command will be something like this:

linux-vdso.so.1 (0x00007ffff8364000)
libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007feb9917a000)
libdl.so.2 => /usr/lib/libdl.so.2 (0x00007feb98f76000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007feb98bf4000)
libm.so.6 => /usr/lib/libm.so.6 (0x00007feb988f6000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007feb986e0000)
libc.so.6 => /usr/lib/libc.so.6 (0x00007feb9833c000)
/lib64/ld-linux-x86-64.so.2 (0x00007feb99397000)

Linux-vdso.so.1 is the name of the library and the hex number is the address where the library is loaded to in memory.

On many lines, the => symbol is followed by a path. This is the path to the physical binary. The hex number is the address where the library is loaded.