ls -l的代码实现

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

#include <pwd.h>
#include <grp.h>
#include <time.h>

void print_file_type(struct stat buf);
void print_access_permission(struct stat buf);
void print_access_permission_data(struct stat buf);

int main(int argc,char **argv)
{
    if(2 !=argc)
    {
        printf("usage:%s file\n",argv[0]);
        exit(1);
    }

    int ret_val = -1;
    struct stat buf;
    ret_val = lstat(argv[1],&buf);
    if(-1 == ret_val)
    {
        perror("lstat");
        exit(1);
    }

    print_file_type(buf);
    print_access_permission(buf);
    printf(" ");
    /*打印链接数*/
    printf("%d ",buf.st_nlink);

    /*获取uid*/
    printf("%s ",getpwuid(buf.st_uid)->pw_name);

    /*获取gid*/
    printf("%s ",getgrgid(buf.st_gid)->gr_name);

    /*获取大小*/
    printf("%ld ",buf.st_size);


    /*获取时间*/
    struct tm *ptime;
    ptime = localtime(&(buf.st_mtime));
    printf("%d-%d-%d %d:%d",ptime->tm_year + 1900,ptime->tm_mon,
            ptime->tm_mday,ptime->tm_hour,ptime->tm_min);

    printf(" ");
    printf("%s\n",argv[1]);
    return 0;

}


void print_file_type(struct stat buf)
{
    if(S_ISREG(buf.st_mode))
    {
        printf("-");
    }
    else if(S_ISDIR(buf.st_mode))
    {
        printf("d");
    }
    else if(S_ISCHR(buf.st_mode))
    {
        printf("c");
    }
    else if(S_ISBLK(buf.st_mode))
    {
        printf("b");
    }
    else if(S_ISFIFO(buf.st_mode))
    {
        printf("p");
    }
    else if(S_ISLNK(buf.st_mode))
    {
        printf("l");
    }
    else if(S_ISSOCK(buf.st_mode))
    {
        printf("s");
    }
}

void print_access_permission(struct stat buf)
{
    /*用户的读写执行权限*/
    if(S_IRUSR & buf.st_mode)
    {
        printf("r");
    }
    else
    {
        printf("-");
    }

    if(S_IWUSR & buf.st_mode)
    {
        printf("w");
    }
    else
    {
        printf("-");
    }

    if(S_IXUSR & buf.st_mode)
    {
        printf("x");
    }
    else
    {
        printf("-");
    }


    /*组读写执行权限*/
    if(S_IRGRP & buf.st_mode)
    {
        printf("r");
    }
    else
    {
        printf("-");
    }

    if(S_IWGRP & buf.st_mode)
    {
        printf("w");
    }
    else
    {
        printf("-");
    }

    if(S_IXGRP & buf.st_mode)
    {
        printf("x");
    }
    else
    {
        printf("-");
    }

    /*其他的读写执行权限*/
    if(S_IROTH & buf.st_mode)
    {
        printf("r");
    }
    else
    {
        printf("-");
    }

    if(S_IWOTH & buf.st_mode)
    {
        printf("w");
    }
    else
    {
        printf("-");
    }

    if(S_IXOTH & buf.st_mode)
    {
        printf("x");
    }
    else
    {
        printf("-");
    }
}

/*
通过buf.st_mode的0-9位屏蔽字来
确定该文件的访问权限
*/
void print_access_permission_data(struct stat buf)
{
    printf("buf:%x\n",buf.st_mode);
    printf("S_IRUSR:%x\n",S_IRUSR);
    printf("S_IWUSR:%x\n",S_IWUSR);
    printf("S_IXUSR:%x\n",S_IXUSR);

    printf("S_IRGRP:%x\n",S_IRGRP);
    printf("S_IWGRP:%x\n",S_IWGRP);
    printf("S_IXGRP:%x\n",S_IXGRP);

    printf("S_IROTH:%x\n",S_IROTH);
    printf("S_IWOTH:%x\n",S_IWOTH);
    printf("S_IXOTH:%x\n",S_IXOTH);
}