Linux系统编程10-模拟实现 ls -l 命令

//-rw-rw-r-- 1 username groupname 112 Wed Sep 14 22:08:30 2022 hello.txt

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

int main(int argc, char const *argv[])
{
    //判断输入的参数是否正确
    if (argc < 2)
    {
        printf("%s filename\n", argv[0]);
        return -1;
    }

    //通过stat函数获取用户传入的文件信息
    struct stat st;
    int ret = stat(argv[1], &st);
    if (ret == -1)
    {
        perror("stat err");
        return -1;
    }

    //获取文件类型和文件权限
    char perms[11] = {0}; //用于保存文件类型和文件权限的字符串

    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;
    }

    //判断文件访问权限
    perms[1] = (st.st_mode & S_IRUSR) ? 'r' : '-';
    perms[2] = (st.st_mode & S_IWUSR) ? 'w' : '-';
    perms[3] = (st.st_mode & S_IXUSR) ? 'x' : '-';

    //文件所在组
    perms[4] = (st.st_mode & S_IRGRP) ? 'r' : '-';
    perms[5] = (st.st_mode & S_IWGRP) ? 'w' : '-';
    perms[6] = (st.st_mode & S_IXGRP) ? 'x' : '-';

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

    //获取硬链接数
    int linkNum = st.st_nlink;

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

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

    //文件大小
    long int fileSize = st.st_size;

    //获取修改时间
    char *time = ctime(&st.st_mtime);
    char mtime[512];
    strncpy(mtime, time, strlen(time) - 1);

    char buf[1024];
    sprintf(buf, "%s %d %s %s %ld %s %s", perms, linkNum, fileUser, fileGroup, fileSize, mtime, argv[1]);
    printf("%s\n", buf);

    return 0;
}