text: /* See LICENSE file for copyright and license details. */
  #include <dirent.h>
  #include <stdbool.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  #include <sys/stat.h>
  
  #define FLAG(x)  (flag[(x)-'a'])
  
  static void test(const char *, const char *);
  
  static bool match = false;
  static bool flag[26];
  static struct stat old, new;
  
  int
  main(int argc, char *argv[]) {
  	struct dirent *d;
  	char buf[BUFSIZ], *p;
  	DIR *dir;
  	int opt;
  	int x = 0;
  
  	while((opt = getopt(argc, argv, "abcdefghln:o:pqrsuwx")) != -1)
  		switch(opt) {
  		case 'n': /* newer than file */
  		case 'o': /* older than file */
  			if(!(FLAG(opt) = !stat(optarg, (opt == 'n' ? &new : &old))))
  				perror(optarg);
  			break;
  		default:  /* miscellaneous operators */
  			FLAG(opt) = true;
  			break;
  		case '?': /* error: unknown flag */
  			fprintf(stderr, "usage: %s [-abcdefghlpqrsuwx] [-n file] [-o file] [file...]\n", argv[0]);
  			exit(2);
  		}
  	if(optind == argc)
  		while(fgets(buf, sizeof(buf), stdin)) {
  			if((p = strchr(buf, '\n')))
  				*p = '\0';
  			test(buf, buf);
  		}
  	for(; optind < argc; optind++)
  		if(FLAG('l') && (dir = opendir(argv[optind]))) {
  			/* test directory contents */
  			while((d = readdir(dir))) {
  				if ((x = snprintf(buf, sizeof(buf), "%s/%s", argv[optind], d->d_name)) < 0)
  					exit(3);
  				if(((size_t)x) < sizeof(buf))
  					test(buf, d->d_name);
  			}
  			closedir(dir);
  		}
  		else
  			test(argv[optind], argv[optind]);
  
  	return match ? 0 : 1;
  }
  
  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)) {                 /* executable        */
  		if(FLAG('q'))
  			exit(0);
  		match = true;
  		puts(name);
  	}
  }
  