List shared or dynamic libraries required by a program

In Linux, the

ldd

is used to find out the shared libraries or dependencies required by a program if it is a dynamic executable. ldd requires the full path to the executable as input.

For instance, the Linux ps command depends on the following shared or dynamic libraries -

[root@kauai rtc0]# ldd $(which ps)
	linux-vdso.so.1 =>  (0x00007ffeb6277000)
	libselinux.so.1 => /lib64/libselinux.so.1 (0x0000003ef6200000)
	libproc-3.2.8.so => /lib64/libproc-3.2.8.so (0x0000003ef4e00000)
	libc.so.6 => /lib64/libc.so.6 (0x0000003ef4a00000)
	libdl.so.2 => /lib64/libdl.so.2 (0x0000003ef5600000)
	/lib64/ld-linux-x86-64.so.2 (0x0000003ef4600000)

You can also use the ldd command to find out if an executable has an expected dependencies. In this case, we expect that the *htpasswd, login and sshd* commands depend on the crypt library as they prompt a user for a password for authentication purposes -


[root@kauai rtc0]# ldd $(which htpasswd) |grep crypt
	libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007f010c8ab000)

[root@kauai rtc0]# ldd $(which login) | grep crypt
	libcrypt.so.1 => /lib64/libcrypt.so.1 (0x0000003efd200000)

[root@kauai rtc0]# ldd $(which sshd) | grep crypt
	libcrypto.so.10 => /usr/lib64/libcrypto.so.10 (0x00007ffb0b1f2000)
	libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007ffb0a988000)
	libk5crypto.so.3 => /lib64/libk5crypto.so.3 (0x00007ffb0a015000)

References -

http://man7.org/linux/man-pages/man1/ldd.1.html

FILED UNDERldd shared dynamic libraries