使用教材

《“笨办法” 学C语言（Learn C The Hard Way）》
https://www.jianshu.com/p/b0631208a794

ex9.c

#include <stdio.h>

int main(int argc, char *argv[])
{
    int i = 25;
    while(i >= 0) {
        printf("%d ",i);
        i--;
    }

    // need this to add a final newline
    printf("\n");

    return 0;
}

Makefile

CC=clang
CFLAGS=-Wall -g

clean:
    rm -f ex9

run

anno@anno-m:~/Documents/mycode/ex9$ make ex9
clang -Wall -g    ex9.c   -o ex9
anno@anno-m:~/Documents/mycode/ex9$ ./ex9
25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0