Linux:open

1.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <fcntl.h>

int main(int argc, char* argv[])
{
    
    
    if ( argc != 3 )
    {
    
    
        printf("arg err\n");
        return 0;
    }

    char * filename = argv[1];
    char * newfilename = argv[2];

    int fdr = open(filename,O_RDONLY);
    int fdw = open(newfilename,O_WRONLY|O_CREAT,0600);
    if ( fdr == -1 || fdw == -1 )
    {
    
    
        printf("open file failed\n");
        return 0;
    }

    char buff[512] = {
    
    0};
    int n = 0;
    while( ( n = read(fdr,buff,512)) > 0 )
    {
    
    
        write(fdw,buff,n);
    }

    close(fdr);
    close(fdw);

    /*
    int fd = open("a.txt",O_RDONLY);
    assert( fd != -1 );

    char buff[128] = {0};
    int n = read(fd,buff,127);// read() == 0   

    printf("buff=%s,n=%d\n",buff,n);

    close(fd);
    */

    /*
    int fd = open("a.txt",O_WRONLY|O_CREAT,0600);
    assert( fd != -1 );

    write(fd,"hello",5);

    close(fd);    

    */
}

7_24
Fork复制进程
僵死进程：子进程先于父进程结束，父进程没有获取子进程的退出码。
文件操作调用：open,read,write,close
Man:1 命令 2 系统调用 3 库函数
Linux 不区分二进制和文本文件，特殊字符
替换进程：exec系列