How do I get the entry point of other binary(executable) in Linux without recompile?

Question

I'm trying to get the entry point of other binary.
I want to write the program in C which hooking the specified function of other binary in Linux.

There are 2 programs.

1. binary (any language, any compile option)
2. The program that executes the hooks

I search how to do that without recompile Program 1.
It is assumed that I know the name of the function specified.

I don't want to modify Program 1. So I need the entry point of function of other binary for hooking without recompile.
On the other hand, Program 2, I can make as many changes as I like.
What should I do?

Here's an overview

Goal:

• How to get the entry point of other binary(executable) in Linux?

Assumes:

1. Program 1 is generated by compiling the C language.(any options)
   It is better if I could support not only C language.

2. Program 2 is generated by compiling the C language.

Requirement:

1. without recompile Program 1.