文件IO-access

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


int access_read_test(const char * filename)
{
    return access(filename, R_OK);
}


int main(int argc, char * argv[])
{
    if (argc < 2)
    {
        printf("usage:./exe file\n");
        exit(EXIT_FAILURE);
    }

    char * buf = "hello";
    char * file = "a.txt";
    int fd = open(file, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
    
    if (fd == -1)
    {
        perror("Error open func.\n");
        exit(EXIT_FAILURE);
    }

    write(fd, buf, strlen(buf));

    const char * filename = NULL;   // 作用？
    filename = argv[1];
    
    if (access_read_test(filename) < 0)
    {
        perror("access read perrmission test: FAIL\n");
    } 
    else
    {
        printf("access read perrmission test: DONE\n");
    }

    exit(EXIT_SUCCESS);
}