1、图片拷贝

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <sys/stat.h>
#include <fcntl.h>

typedef struct xccpy
{
    int num;
    off_t size;
    int fd_r;
    int fd_w;
}cpy;
void* hello(void*arg)
{
    char c;
    for(((cpy*)arg)->num=0;((cpy*)arg)->num<(((cpy*)arg)->size)/2;(((cpy*)arg)->num)++)
    {
        read(((cpy*)arg)->fd_r,&c,1);
        write(((cpy*)arg)->fd_w,&c,1);
    }
}
                                                                                                                 
int main( int argc, const char *argv[])
{
    struct xccpy xc;
    xc.num=0;
    xc.size=lseek(xc.fd_r,0,SEEK_END);

    xc.fd_r=open("./1.jpg",O_RDONLY);
    if(xc.fd_r<0)
    {
        perror("open");
        return -1;
    }
    xc.fd_w=open("./2.jpg",O_WRONLY|O_CREAT,0664);
    if(xc.fd_w<0)
    {
        perror("open");
        return -1;
    }
    pthread_t tid;
    pthread_create(&tid,NULL,hello,(void*)&xc);
    int i=0;
    char c;
    while(xc.num>=(xc.size)/2)
    {
        for(i=(xc.size)/2;i<xc.size;i++)
        {
            read(xc.fd_r,&c,1);
            write(xc.fd_w,&c,1);
            (xc.num)++;
        }
    }

    return 0;
}

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
char buf[]="1234567";
void *fz(void*arg)
{
    int i=0;
    int j=6;
    for(;i<j;i++,j--)
    {
        ((char*)arg)[i]=((char*)arg)[i]^((char*)arg)[j];
        ((char*)arg)[j]=((char*)arg)[i]^((char*)arg)[j];
        ((char*)arg)[i]=((char*)arg)[i]^((char*)arg)[j];

    }
}
int main( int argc, const char *argv[])                          
{
    
    pthread_t tid;
    pthread_create(&tid,NULL,fz,(void*)&buf);
    int i=0;
    while(1)
    {
        printf("%s\n",buf);
    }
    return 0;
}