ldd本身不是一个程序，而仅是一个shell脚本：ldd可以列出一个程序所需要得动态链接库（so）
[root@xiaolizi ~ ]$ ldd /usr/bin/ls
linux-vdso.so.1 => (0x00007ffc91c56000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f9ffa9f4000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f9ffa7ef000)
libacl.so.1 => /lib64/libacl.so.1 (0x00007f9ffa5e5000)
libc.so.6 => /lib64/libc.so.6 (0x00007f9ffa222000)
libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f9ff9fc0000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f9ff9dbb000)
/lib64/ld-linux-x86-64.so.2 (0x00005654fcee0000)
libattr.so.1 => /lib64/libattr.so.1 (0x00007f9ff9bb6000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f9ff999a000)