Segfault when executing chattr clone

Question

I implemented the chattr command but I have a problem. When I give them ./chattr in the terminal I receive segmentation fault (core dumb), I should have seen the list of attributes. How can I fix this problem and stop showing it to me?

program:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/fs.h>

void usage_error()
{
    printf("usage: chattr [mode] files...\n");
    exit(EXIT_FAILURE);
}

int main(int argc, char *argv[])
{
    int fd, modify, attr, new_attr = 0;

    modify = argv[1][0];
    for (int i = 1; argv[1][i] != '\0'; ++i)
    {
        switch (argv[1][i])
        {
        case 'a':
            new_attr |= FS_APPEND_FL;
            break;

        case 'A':
            new_attr |= FS_NOATIME_FL;
            break;

        case 'c':
            new_attr |= FS_COMPR_FL;
            break;

        case 'd':
            new_attr |= FS_NODUMP_FL;
            break;

        case 'D':
            new_attr |= FS_DIRSYNC_FL;
            break;

        case 'i':
            new_attr |= FS_IMMUTABLE_FL;
            break;

        case 'j':
            new_attr |= FS_JOURNAL_DATA_FL;
            break;

        case 's':
            new_attr |= FS_SECRM_FL;
            break;

        case 'S':
            new_attr |= FS_SYNC_FL;
            break;

        case 't':
            new_attr |= FS_NOTAIL_FL;
            break;

        case 'T':
            new_attr |= FS_TOPDIR_FL;
            break;

        case 'u':
            new_attr |= FS_UNRM_FL;
            break;

        default:
            usage_error();
            break;
        }
    }

    for (int i = 2; i < argc; ++i)
    {
        if ((fd = open(argv[i], O_RDONLY)) == -1)
        {
            fprintf(stderr, "%s open failed\n", argv[i]);
            continue;
        }

        if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == -1)
        {
            fprintf(stderr, "ioctl get flags failed\n");
            close(fd);
            continue;
        }

        switch (modify)
        {
        case '+':
            attr |= new_attr;
            break;

        case '-':
            attr &= (~new_attr);
            break;

        case '=':
            attr = new_attr;
            break;

        default:
            usage_error();
            break;
        }

        if (ioctl(fd, FS_IOC_SETFLAGS, &attr) == -1)
            fprintf(stderr, "ioctl set flags failed\n");

        close(fd);
    }

    return 0;
}