Compile C program under linux

gistfile1.sh

$ vi hello.c
# #include <stdio.h>
# 
# int main() {
#   printf("Hello world!\n");
#   exit(0);
# }

$ gcc -o hello hello.c
hello.c: In function ‘main’:
hello.c:5:3: warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default]
$ ./hello 
Hello, world!

$ vi fred.c
# #include <stdio.h>
# 
# void fred(int arg) {
#   printf("fred: you have passed %d\n", arg);
# }

$ vi bill.c 
# #include <stdio.h>
# 
# void bill(char *arg) {
#   printf("bill: you have passed %s\n", arg);
# }

$ gcc -c fred.c bill.c 
$ ls *.o
bill.o  fred.o

$ vi lib.h
# /* This is lib.h. It declares the functions fred and bill for users */
# 
# void fred(int arg);
# void bill(char *arg);

$ vi program.c
# #include "lib.h"
# 
# int main() {
#   bill("Hello World!");
#   fred(123);
#   return 0;
# }
$ gcc -c program.c
$ gcc -o program program.o fred.o bill.o
$ ./program
bill: you have passed Hello World!
fred: you have passed 123

# create a static library
$ ar crv libfoo.a fred.o bill.o
a - bill.o
a - fred.o
$ ls libfoo.a
libfoo.a
$ ranlib libfoo.a

# linking static library
$ gcc -o program1 program.o libfoo.a
$ ls program1
program1

# list a program's neccessary share libraries
$ ldd program1
  linux-gate.so.1 =>  (0xb7727000)
	libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb756a000)
	/lib/ld-linux.so.2 (0xb7728000)