LD_DEBUG and LD_LIBRARY_PATH

It is useful to find out which library are loaded when running the program.

LD_DEBUG = help ./a.out

Vaild option for LD_DEBUG
libs	display library search paths
reloc	display relocation processing
files	display progress for input file
symbols	display symbol table processing
bindings	display information about symbol binding
versions	display version dependencies
all	all previous options combined
statistics	display relocation statistic
unused	determined unused DSOs
help	display this help message and exit

LD_DEBUG=libs ./a.out

17315:    find library=libc.so.6 [0]; searching
17315:     search cache=/etc/ld.so.cache
17315:      trying file=/lib/tls/i686/cmov/libc.so.6
17315:
17315:
17315:    calling init: /lib/tls/i686/cmov/libc.so.6
17315:
17315:
17315:    initialize program: ./a.out
17315:
17315:
17315:    transferring control: ./a.out
17315:
17315:
17315:    calling fini: ./a.out [0]
17315:
17315:
17315:    calling fini: /lib/tls/i686/cmov/libc.so.6 [0]
17315:

From above result, it will find the file "ld.so.conf" to know where the standard library is located.
In this case, the library I only use is glibc. So it is a simple code.
But it is handy tool if your program is very complex and you want to know which library is linked.

gcc --share b.c -o libb.so
gcc -o a{,.c} -lb -L.

Then you should export libary PATH "LD_LIBRARY_PATH"

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH;./

The program will be executed successfully.
You can try LD_DEBUG again and the loader will search additional path "./" you assigned  and load the specific library to memory.