stat函数及ls功能

stat filename 

查看文件信息

---

stat函数

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

int stat(const char *pathname, struct stat *buf);

ls -l filename 功能的实现：

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <string.h>

int main(int argc, char* argv[])
{
    if(argc < 2){
        printf("参数错误 argc < 2
");
        exit(1);
    }

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

    char perms[11]={0};
    //判断文件类型
    switch(st.st_mode & S_IFMT)
    {
        case S_IFLNK:
            perms[0] = "l";
            break;
        case S_IFDIR:
            perms[0] = "d";
            break;
        case S_IFREG:
            perms[0] = "-";
            break;
        case S_IFBLK:
            perms[0] = "b";
            break;
        case S_IFCHR:
            perms[0] = "c";
            break;
        case S_IFSOCK:
            perms[0] = "s";
            break;
        case S_IFIFO:
            perms[0] = "P";
            break;
        default:
            perms[0] = "?";
            break;
    }

    //判断文件的访问权限

    //文件所有者
    perms[1] = (st.st_mode & S_IRUSR) ? "r" : "-";
    perms[2] = (st.st_mode & S_IWUSR) ? "w" : "-";
    perms[3] = (st.st_mode & S_IXUSR) ? "x" : "-";

    //group
    perms[4] = (st.st_mode & S_IRGRP) ? "r" : "-";
    perms[5] = (st.st_mode & S_IWGRP) ? "w" : "-";
    perms[6] = (st.st_mode & S_IXGRP) ? "x" : "-";

    //others
    perms[7] = (st.st_mode & S_IROTH) ? "r" : "-";
    perms[8] = (st.st_mode & S_IWOTH) ? "w" : "-";
    perms[9] = (st.st_mode & S_IXOTH) ? "x" : "-";

    //硬链接计数
    int linkNum = st.st_nlink;

    //文件所有者
    char* fileUser = getpwuid(st.st_uid)->pw_name;

    //文件所属组
    char* fileGroup = getgrgid(st.st_gid)->gr_name;

    //文件大小
    int fileSize = (int)st.st_size;

    //修改时间
    char* time = ctime(&st.st_mtime);
    char mtime[512]={0};
    strncpy(mtime, time, strlen(time)-1);
    char buf[1024];
    sprintf(buf, "%s %d %s %s %d %s %s",perms, linkNum, fileUser, fileGroup, fileSize, mtime, argv[1]);
    printf("%s
", buf);

    return 0;
}