man unbuffer

truncate -s 2M fs.img
mkfs.ext2 fs.img
mkdir ./tmpdir
sudo mount -o loop fs.img ./tmpdir/
sudo touch ./tmpdir/a # add your desired number of files
sudo umount ./tmpdir

#include <cstdint>
#include <fcntl.h>
#include <linux/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define EXT2_NDIR_BLOCKS 12
#define EXT2_IND_BLOCK EXT2_NDIR_BLOCKS
#define EXT2_DIND_BLOCK (EXT2_IND_BLOCK + 1)
#define EXT2_TIND_BLOCK (EXT2_DIND_BLOCK + 1)
#define EXT2_N_BLOCKS (EXT2_TIND_BLOCK + 1)
struct ext2_inode {
    __le16 i_mode;        /* File mode */
    __le16 i_uid;         /* Low 16 bits of Owner Uid */
    __le32 i_size;        /* Size in bytes */
    __le32 i_atime;       /* Access time */
    __le32 i_ctime;       /* Creation time */
    __le32 i_mtime;       /* Modification time */
    __le32 i_dtime;       /* Deletion Time */
    __le16 i_gid;         /* Low 16 bits of Group Id */
    __le16 i_links_count; /* Links count */
    __le32 i_blocks;      /* Blocks count */
    __le32 i_flags;       /* File flags */
    union {
        struct {
            __le32 l_i_reserved1;
        } linux1;
        struct {
            __le32 h_i_translator;
        } hurd1;
        struct {
            __le32 m_i_reserved1;
        } masix1;
    } osd1;                        /* OS dependent 1 */
    __le32 i_block[EXT2_N_BLOCKS]; /* Pointers to blocks */
    __le32 i_generation;           /* File version (for NFS) */
    __le32 i_file_acl;             /* File ACL */
    __le32 i_dir_acl;              /* Directory ACL */
    __le32 i_faddr;                /* Fragment address */
    union {
        struct {
            __u8 l_i_frag;  /* Fragment number */
            __u8 l_i_fsize; /* Fragment size */
            __u16 i_pad1;
            __le16 l_i_uid_high; /* these 2 fields    */
            __le16 l_i_gid_high; /* were reserved2[0] */
            __u32 l_i_reserved2;
        } linux2;
        struct {
            __u8 h_i_frag;  /* Fragment number */
            __u8 h_i_fsize; /* Fragment size */
            __le16 h_i_mode_high;
            __le16 h_i_uid_high;
            __le16 h_i_gid_high;
            __le32 h_i_author;
        } hurd2;
        struct {
            __u8 m_i_frag;  /* Fragment number */
            __u8 m_i_fsize; /* Fragment size */
            __u16 m_pad1;
            __u32 m_i_reserved2[2];
        } masix2;
    } osd2; /* OS dependent 2 */
};

struct ext2_dirent {
    __u32 inode;
    __u16 rlen;
    __u8 nlen;
    __u8 ttype;
};

int main(int argc, char *argv[]) {
    FILE *fs = fopen("fs.img", "r+");
#define ROOT_INODE_BLK 12
#define BSIZE 1024
#define ROOT_INODE_IDX 2
#define INODE_SIZE 256
#define BPTR(id) ((id) * BSIZE)
#define INODE_PTR(id) (BPTR(ROOT_INODE_BLK) + (id) * INODE_SIZE)
    // #define
    // printf("x %lu\n", sizeof(struct ext2_inode));
    //

    struct ext2_inode nd;
    fseek(fs, INODE_PTR(1), SEEK_SET);
    fread(&nd, sizeof(nd), 1, fs);

    __u8 dat[BSIZE];
    __u32 blkptr = BPTR(nd.i_block[0]);
    fseek(fs, blkptr, SEEK_SET);
    fread(dat, sizeof(dat), 1, fs);

    // printf("%x\n", nd.i_mode);

    __u8 *ptr = dat;
    struct ext2_dirent dirent;

    int i = 0;
    do {
        memcpy(&dirent, ptr, sizeof(dirent));

        if (i++ > 0) {
            dirent.nlen = 1;
            memcpy(ptr, &dirent, sizeof(dirent));
            memcpy(ptr + sizeof(dirent), "..", 1);
        }

        printf("%u %u %u %u %.*s\n", dirent.inode, dirent.rlen, dirent.nlen,
               dirent.ttype, dirent.nlen, (char *)(ptr + sizeof(dirent)));
        ptr += dirent.rlen;
    } while (ptr < dat + BSIZE);

    fseek(fs, blkptr, SEEK_SET);
    fwrite(dat, sizeof(dat), 1, fs);
}

g++ wtf.c && ./a.out
sudo mount -o loop fs.img ./tmpdir/
/bin/ls ./tmpdir