The C Programming Language

To be continued...
第8章 UNIX系统接口
#include <stdio.h>
#include <fcntl.h>
#include "syscalls.h"
#defien PERMS 0666
void error(char *, ...);
/* cp函数: 将 f1 复制到 f2 */
int main(int argc, char *argv[])
{
    int f1, f2, n;
    char buf[BUFSIZ];
   
    if (argc != 3)
        error("Usage: c from to");
    if ((f1 = open(argv[1], O_RDONLY, 0)) == -1)
        error("cp: can't open %s", argv[1]);
    if ((f2 = creat(argv[2], PERMS)) == -1)
        error("cp: can't create %s, mode %03o", argv[2], PERMS);
    while ((n = read(f1, buf, BUFSIZ)) > 0)
        if (write(f2, buf, n) != n)
            error("cp: write error on file %s", argv[2]);
    return 0;
}
#include <stdio.h>
#include <stdarg.h>
/* error函数: 打印一个出错信息，然后终止 */
void error(char *fmt, ...)
{
    va_list args;
   
    va_start(args, fmt);
    fprintf(stderr, "error:");
    vfprintf(stderr, fmt, args);
    fprintf(stderr, "\n");
    va_end(args);
    exit (1);
}