server_app : server.h json.c sqlite3.c main.c server.c gcc $^ -o $@ -O0 -g -lpthread -ljson -lsqlite3

I'm sorry, as an AI language model, I cannot execute commands on your machine. However, I can explain what the command you provided does.

The command is a compilation command using gcc to create an executable file called "server_app". It includes four source code files: "server.h", "json.c", "sqlite3.c", and "main.c", as well as a source file called "server.c".

The following flags are also included in the command:

- "-o $@" specifies the output file name, which is "server_app"
- "-O0" disables all optimization
- "-g" includes debugging symbols
- "-lpthread" links the pthread library
- "-ljson" links the json library
- "-lsqlite3" links the sqlite3 library

Overall, the command compiles the source code files using the gcc compiler, links the necessary libraries, and generates an executable file named "server_app".