#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <stdio.h>

int main()

{

    int fd;

    fd = open("abc.txt", O_CREAT|O_RDWR, ); // 若flag中使用了O_CREAT,则需要指定第三个参数访问权限

    if (fd < )

        printf("file create failure");

    printf("current fd is: %d\n", fd);

    close(fd);

    return ;

}

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <unistd.h>

#include <string.h>

static const char *str = "http://www.baidu.com\n";

int main()

{

    int fd;

    fd = open("cde.txt", O_CREAT|O_RDWR|O_APPEND, );

    write(fd, str, strlen(str));

    close(fd);

    return ;

}

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <string.h>

#include <unistd.h>

#include <stdio.h>

int main()

{

    char tmp[];

    char str[]; 

    int wr_fd;

    wr_fd = open("aaa.txt", O_CREAT|O_WRONLY|O_APPEND, );

    int rd_fd;

    rd_fd = open("cde.txt", O_RDONLY);

    int total = , len;

    while((len = read(rd_fd, tmp, ))) {

        strncpy(str+total, tmp, len);

        total+=len;

    }

    str[total-] = '\0';

    close(wr_fd);

    close(rd_fd);

    printf("str is: %s\n", str);

    return ;

}

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <unistd.h>

#include <string.h>

static const char *str = "http://www.ibm.com\n";

int main()

{

    int fd;

    off_t offset;

    fd = open("cde.txt", O_RDWR);

    offset = lseek(fd, , SEEK_END);

    write(fd, str, strlen(str));

    close(fd);

    printf("cur offset is: %d\n", offset);

    return ;

}

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <unistd.h>

#include <stdio.h>

int main()

{

    int fd;

    off_t offset;

    fd = open("cde.txt", O_RDWR);

    offset = lseek(fd, , SEEK_END);

    printf("cur file size is: %d\n", offset);

    close(fd);

    return ;

}

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <errno.h>

#include <stdlib.h>

#include <unistd.h>

#include <stdio.h>

int main()

{

    int fd;

    if ((fd = open("hh.txt", O_RDWR | O_CREAT | O_EXCL, )) == -) {

        perror("open error");

        exit();

    }    

    int var;

    if ((var = fcntl(fd, F_GETFL, )) < ) {

        perror("fcntl error");

        close(fd);

        exit();

    }

    switch(var & O_ACCMODE) {

        case O_RDONLY:

            printf("Read only ...\n");

        break;

        case O_WRONLY:

            printf("Write only ...\n");

        break;

        case O_RDWR:

            printf("Read And Write ...\n");

        break;

        default:

            printf("Do't know...\n");

        break;

    }

    if (var & O_APPEND) {

        printf("And Append...\n");

    }

    if (var & O_NONBLOCK) {

        printf("And Blocking...\n");

    }

    if (close(fd) == -) {

        perror("close error");

    }

    return ;

}

#include <sys/ioctl.h>

#include <stdio.h>

#include <errno.h>

#include <stdlib.h>

#include <unistd.h>

int main()

{

    struct winsize size;

    if (isatty(STDOUT_FILENO) == )

        exit();

    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &size) < ) {

        perror("ioctl TIOCGWINSZ error");

        exit();

    }

    printf("%d rows, %d columns\n", size.ws_row, size.ws_col);

    return ;

}