#include <sys/stat.h>

#include <dirent.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

char *argv0;

#define FLAG(x)  (flag[(x) - 'a'])

static void test(const char *, const char *);
static void usage();

static int match = 0;
static int flag[26];
static struct stat old, new;

static void test(const char *path, const char *name) {
    struct stat st, ln;

    if ((!stat(path, &st) && (FLAG('a') || name[0] != '.')        /* hidden files      */
    && (!FLAG('b') || S_ISBLK(st.st_mode))                        /* block special     */
    && (!FLAG('c') || S_ISCHR(st.st_mode))                        /* character special */
    && (!FLAG('d') || S_ISDIR(st.st_mode))                        /* directory         */
    && (!FLAG('e') || access(path, F_OK) == 0)                    /* exists            */
    && (!FLAG('f') || S_ISREG(st.st_mode))                        /* regular file      */
    && (!FLAG('g') || st.st_mode & S_ISGID)                       /* set-group-id flag */
    && (!FLAG('h') || (!lstat(path, &ln) && S_ISLNK(ln.st_mode))) /* symbolic link     */
    && (!FLAG('n') || st.st_mtime > new.st_mtime)                 /* newer than file   */
    && (!FLAG('o') || st.st_mtime < old.st_mtime)                 /* older than file   */
    && (!FLAG('p') || S_ISFIFO(st.st_mode))                       /* named pipe        */
    && (!FLAG('r') || access(path, R_OK) == 0)                    /* readable          */
    && (!FLAG('s') || st.st_size > 0)                             /* not empty         */
    && (!FLAG('u') || st.st_mode & S_ISUID)                       /* set-user-id flag  */
    && (!FLAG('w') || access(path, W_OK) == 0)                    /* writable          */
    && (!FLAG('x') || access(path, X_OK) == 0)) != FLAG('v')) {   /* executable        */
        if (FLAG('q')) {
            exit(0);
        }
        match = 1;
        puts(name);
    }
}

static void usage() {
    fprintf(stderr, "usage: %s [-abcdefghlpqrsuvwx] "
            "[-n file] [-o file] [file...]\n", argv0);
    exit(2); /* like test(1) return > 1 on error */
}

int main(int argc, char *argv[]) {
    struct dirent *d;
    char path[PATH_MAX], *line = NULL, *file;
    size_t linesiz = 0;
    ssize_t n;
    DIR *dir;
    int r;

    for (argv0 = *argv, argv++, argc--; argv[0] && argv[0][0] == '-' && argv[0][1]; argc--, argv++) {
        char argc_;
        char **argv_;
        int brk_;

        if (argv[0][1] == '-' && argv[0][2] == '\0') {
            argv++;
            argc--;
            break;
        }

        for (brk_ = 0, argv[0]++, argv_ = argv; argv[0][0] && !brk_; argv[0]++) {
            if (argv_ != argv) {
                break;
            }
            argc_ = argv[0][0];
            switch (argc_) {
                case 'n': /* newer than file */
                case 'o': /* older than file */
                    file = ((argv[0][1] == '\0' && argv[1] == NULL)?
                            ((usage()), abort(), (char *)0) : (brk_ = 1, (argv[0][1] != '\0')?
                            (&argv[0][1]) : (argc--, argv++, argv[0])));

                    if (!(FLAG(argc_) = !stat(file, (argc_ == 'n' ? &new : &old)))) {
                        perror(file);
                    }
                    break;
                default:
                    /* miscellaneous operators */
                    if (strchr("abcdefghlpqrsuvwx", argc_)) {
                        FLAG(argc_) = 1;
                    } else {
                        usage(); /* unknown flag */
                    }
            }
        }
    };

    if (!argc) {
        /* read list from stdin */
        while ((n = getline(&line, &linesiz, stdin)) > 0) {
            if (n && line[n - 1] == '\n') {
                line[n - 1] = '\0';
            }
            test(line, line);
        }
        free(line);
    } else {
        for (; argc; argc--, argv++) {
            if (FLAG('l') && (dir = opendir(*argv))) {
                /* test directory contents */
                while ((d = readdir(dir))) {
                    r = snprintf(path, sizeof path, "%s/%s", *argv, d -> d_name);
                    if (r >= 0 && (size_t)r < sizeof path) {
                        test(path, d -> d_name);
                    }
                }
                closedir(dir);
            } else {
                test(*argv, *argv);
            }
        }
    }
    return match ? 0 : 1;
}
