c库：
#include <stdio.h>
int main(int argc,char *argv[])
{
FILE *p=NULL,*q=NULL;
char *ptr;
ptr=(char *)malloc(sizeof(char)*16);//如果没开辟空间的话会出现段错误。
if(argc<3)
printf("usage:copy file1 to file2");
if((p= fopen(argv[1],"r"))==NULL)
printf("open file1 fail");
else
{
if((q=fopen(argv[2],"a+"))==NULL)
printf("open file: %s fail",argv[2]);
else
while((!feof(p))&&(fread((void *)ptr,16,1,p)==1))
{
if(fwrite((void *)ptr,16,1,q)!=1)
printf("write file :%s error",argv[2]);
}
}
close(p);
close(q);
free(ptr);
}
系统调用：
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
int main(int argc,char *argv[])
{
int fd,to_fd;
char buf[128]={0};
int readbyte,writebyte;
char *ptr;
if(argc<3)
{
printf("usage:copy file1 to file2/n");
exit(-1);
}
fd=open(argv[1],O_RDONLY);
if(fd<0)
printf("open file:%s error/n",argv[1]);
to_fd=open(argv[2],O_RDWR|O_APPEND|O_CREAT,S_IRWXU);
if(to_fd<0)
{
printf("open file:%s error/n",argv[2]);
exit(-2);
}
while(readbyte=read(fd,buf,128))
{
if(readbyte==-1)
{
printf("read file:%s error/n",argv[2]);
exit(-3);
}
else
{
ptr=buf;
if((writebyte=write(to_fd,ptr,readbyte)==-1))
{
printf("wtite file:%s error/n",argv[2]);
exit(-4);
}
}
}
close(fd);
close(to_fd);
free（ptr）；
}