unix环境高级编程--不带缓冲的IO操作-蒲公英云

unix环境高级编程--不带缓冲的IO操作

最近在学习linux环境下的编程，《UNIX环境高级编程》自不用说，是经典中的经典了。下面贴出我的测试代码，测试环境ubuntu11.10， gcc编译通过

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
char buf1[] = "abcdefghij";
char buf2[] = "ABCDEFGHIJ";
void stdio_test();
int main(int argc, char *argv[])
{
//    iotest();
    stdio_test();
    return 0;
}
#define BUFFSIZE 4096
void stdio_test()
{
    int n;
    char buf[BUFFSIZE];
    while ((n = read(STDIN_FILENO, buf, BUFFSIZE)) > 0)
    {
        if (write(STDOUT_FILENO, buf, n) != n)
        {
            printf("write err\n");
        }
    }
    if (n < 0)
    {
        printf("read err");
    }
    exit(0);
}
void iotest()
{
    int fd = 0;
    int iRet = 0;
    char buf_to_read[30] = {0};
    fd = open("example", O_RDWR | O_CREAT, 00644);
    if (fd == -1)
    {
        printf("open err\n");
        return;
    }
    if (write(fd, buf1, 10) != 10)
    {
        printf("write buf1 err\n");
        return;
    }
//这个地方lseek一定要有，否则下一步read会失败，目的是将文件偏移指针移到文件首，因为write会更改文件偏移指针
    if (lseek(fd, 0, SEEK_SET) == -1)
    {
        printf("lseek err\n");
        return;
    }
    if (read(fd, buf_to_read, 30) == -1)
    {
        printf("read err\n");
        return;
    }
    printf("read: %s\n", buf_to_read);
    exit(0);
}