C Starting

On CS Systems - gcc

For CS courses that use C, the gcc compiler is often used. This is already installed on the CS server. To get started do the following.

• Use a terminal text editor (see Text Editors) to edit your C program file. Let's say your program is hello.c
• Compile the program using the gcc command:

gcc hello.c -o hello.o

If you do not have any errors in your program, the file hello.o will be created.

• Run the program by running:

./hello.o

You can use the classic "hello world" program as a first attempt.

#include <stdio.h>

int main(int argc, char *argv[]) {
  printf("Hello world!\n");
  return 0;
}

Makefile

Rather than type the gcc command each time you want to compile, you can put the right commands into a Makefile and use the make command. The following is a basic Makefile which will compile all .c files in the current directory.

SHELL = /bin/sh
CFLAGS = -g -Wall -O0
SRCS = $(wildcard *.c)
OBJS = $(SRCS:.c=.o)

all: $(OBJS)

%.o : %.c
	gcc $(CFLAGS) $< -o $@

clean:
	rm -f *.o

Save this file with the filename Makefile. Then type make to compile all of the .c files. Type make clean</clean> to remove the compiled .o files, to then recompile all .c files with the next make command.

Note that the make command invokes GNU Make, which is documented at https://www.gnu.org/software/make/manual/make.html